Research ArticleStructure and Stability of Cocoa Flowers andTheir Response to Pollination

Kofi Frimpong-Anin1 Michael K Adjaloo2 Peter K Kwapong1 and William Oduro3

1 Department of Entomology and Wildlife School of Biological Sciences University of Cape Coast Cape Coast Ghana2 Technology Consultancy Centre College of Engineering Kwame Nkrumah University of Science and Technology Kumasi Ghana3Department of Wildlife and Range Management Faculty of Renewable Natural ResourcesCollege of Agriculture and Natural Resources Kwame Nkrumah University of Science and Technology Kumasi Ghana

Correspondence should be addressed to Michael K Adjaloo mkadjaloogmailcom

Received 28 August 2013 Revised 31 December 2013 Accepted 10 January 2014 Published 2 March 2014

Academic Editor Curtis C Daehler

Copyright copy 2014 Kofi Frimpong-Anin et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

This study investigated the position of staminodes around the style of cocoa flowers and the stability of cocoa flowers relative topollination and seasonality Cocoa flowers were categorized into convergingle120mm parallel 121ndash240mm and splayge241mmdepending on the distance between the staminode and style Some flowers were hand pollinated while others were not and wereexcluded from insect visitors Proportions of flowers of converging (560) parallel (375) and splay (65) remained similaralong the vertical plane of cocoa trees Although pollination rates of flowers with splay staminodes were the lowest the overallpollination success of cocoa trees was not significantly affected because of the small proportion of splay flowersThe stability of thecocoa flowers depended on both the season and pollination During the dry season unpollinated flowers of cocoa trees showed aflower-stability ratio of 72 on the second day while the flower-stability ratio was 94 in the wet season Pollinated (senescent)flowers had a stability ratio of 95 after 5 days during the wet season but all pollinated flowers dropped after 5 days in the dryseason indicating that seasonal factors such as water stress can have dramatic effects on cocoa yields

1 Introduction

Very low fruit set of cocoa relative to the numerous flowersthe tree produces has been reported by several researchers(eg [1 2]) This implies that there is obviously a delicatebalance between crop success and failure Factors identi-fied include scarcity of the main pollinators (ceratopogonidmidges) especially in the dry season [3ndash5] Some authors[6 7] argued that the spatial arrangement of staminodesaround the style of the cocoa flower affects pollination successand hence may limit fruit set Others [8ndash10] also believedthat cocoa flowers are nectarless and odourless Young et al[11] have demonstrated the presence of microscopic nectarieson the pedicels sepals and guide lines of the petals andstaminodes that produce odour These characteristics of thecocoa flower seem to make it unattractive to many potentialpollinators and therefore only insects that have evolved withthe plant will successfully pollinate it The morphological

and behavioural characteristics of ceratopogonid midgeshowever make them effective pollinators of cocoa [3 12 13]

According to [7] midges are attracted to the verticallyoriented staminodes and use it for landing The dorsal partof the thorax of the midges brushes against the style therebysmearing the style with pollen grains as themidge probes anddescends toward the base of the staminodes after landingon the inner surface of a staminode The fact that stylepollination generally results inmore fruit set than stigma pol-linationmakes the ceratopogonidmidges efficient pollinatingcandidates [14] The insect may then proceed into the petalhood along the purple coloured guide lines where curvedbristles on the thorax press against the anther thereby pickingup pollen grains Kaufmann [7] argued that staminodeswhich splay away from the style are not efficiently pollinateddue to the widened staminode-style gap There is howeverno empirical evidence as to what staminode-style distancereduces pollination efficiency of cocoa flowers ldquoAchieving

Hindawi Publishing CorporationJournal of BotanyVolume 2014 Article ID 513623 6 pageshttpdxdoiorg1011552014513623

2 Journal of Botany

(a) Converging (b) Parallel (c) Splay

Figure 1 Cocoa flowers showing different staminode (arrowed) arrangement

maximum pollination is necessary for optimum yieldrdquo [15]It is therefore essential to acquire sound knowledge of thepollination ecology of cocoa which has been largely ignoredover the years [16 17] Winder and Silva [18] have observedthat in order to enhance knowledge on natural pollinationand hence the crop yield the characteristics of the cocoa treeand its flowersmust be consideredThis calls for some studiesof floral phenology of cocoa trees as well as flower persistenceand stability

This study therefore evaluated the staminode-style dis-tance in relation to fruit set of cocoa and the distribution ofthe different types of staminode-style arrangements along thevertical plane of the cocoa tree In addition the stability of thecocoa flowers under the dry and wet seasons was assessed todetermine their response to pollination

2 Methodology

21 Study Site The study was conducted from 2009 to2010 in two cocoa farms (N05∘194101015840 W001∘242111015840 andN05∘195161015840 W001∘241071015840) at Abrafo in the Twifo HemangLower Denkyira of the Central Region of Ghana togetherwith ten cocoa farms (6∘401015840364s N and 1∘211015840445s W)located at various distances to the Bobiri Forest Reserve atKubease in the Ejisu-Juaben District Ashanti Region All thefarms hadmixtures of hybrid and Upper Amazon varieties of15ndash25-year-old trees Each farm was divided into 4 quadrants(plots) each measuring 12 plusmn 02SD acres

22 Categorisation of Staminode-Style Distance A total of600 cocoa flowers (approximately 75 per plot) were randomlypicked from the trees together with fresh flowers that haddropped to the ground The flowers were put into glass jarswith moistened cotton wool at the base to prevent themfrom withering Distances between the style and 2 randomlyselected staminodes were measured in the laboratory undera stereomicroscope for each flower and the mean (plusmnSD) dis-tance between the staminode and stylewas determined Peaksand troughs of a distribution curve obtained by plottingmeanstaminode-style distance and their frequencies were used todetermine intervals for various flower categories Based onthese the flowers were categorized to three staminode typesconverging parallel and splay (Table 1 and Figure 1)

Table 1 Categorized staminode-style distance and percent fruit set

Type ofstaminoderelative tostyle

Style-staminodedistance (mm)

Per staminodetype Fruit setlowast

Converging le120 560 118a

Parallel 121ndash240 375 156a

Splay ge241 65 05blowastThe fruit set with the same letters is not significantly different

23 Distribution of Staminode Types along the Vertical Planeof Cocoa Trees Eight cocoa trees were randomly selectedfrom each plot and 3 vertical sections of the trunk at heights030ndash130m 131ndash230m and 231ndash330m were marked withpermanent marker Thirty buds which were due to openwithin the next 24 hours within each marked trunk heightwere also marked for each plot Matured buds about toopen can be identified by the prominence of grooves alongjoined edges of sepals where they burst open Buds thatopened about 24 hours after marking were plucked andimmediately put into glass jars with moistened cotton woolat the base Flowers from each trunk section were put indifferent labeled jars Flowers were carefully placed sideways(Figure 1) in the jars and were also spaced out to preventthe staminodes from tangling and subsequent altering oftheir spatial arrangement Staminode-style distances weremeasured as aforementioned in the laboratory This wasrepeated weekly for 6 weeks

24 Relationship between Staminode-Style Distance and Polli-nation Success The staminode type distribution experimentabove was repeated but in this case marked flowers budswere inspected after 72 hours All marked flowers that haddropped to the ground within the period were collectedand their staminode-style distances measured as beforeUnpollinated flowers usually drop off the tree after 48 hours[19] and thus flowers remaining on the tree after the 72-hourperiod were considered pollinated Success of pollination ofeach staminode-style type was estimated indirectly basedon the hypothesis that proportions of flowers that drop(unpollinated) should be comparable to that obtained inthe earlier experiment used to standardized staminode-styledistance categories if their efficiencies are similar

Journal of Botany 3

25 Flower Stability and Pollination A study was carried outduring two dry (JanuaryndashMarch) andwet (MayndashJuly) seasonsto determine the floral stability of cocoa flowers (ie howlong the flowers stayed when unpollinated or pollinated)By a simple random sampling approach one hundred andeleven (111) cocoa trees were selected from ten (10) cocoafarms A total of 555 (five flowers per tree) freshly openedcocoa flowers were randomly sampled from the selectedtrees for the study These flowers were covered with muslincloth to prevent contact with any insect A second set offlowers were selected and manually pollinated following thestandard manual cross-pollination of rubbing three anthersfrom flowers of three different trees against the subjectflowerrsquos stigma ensuring the likelihood of optimal pollination[20 21] A floral census was taken of both pollinated andunpollinated flowers from the second till the fifth day Thewhole process was repeated for each season while observingall exogenous factors that could affect floral stability

26 Data Analysis Chi-square analyses of proportions of thethree staminode-style types at different trunk heights werecompared to the expected proportions (values obtained inthe staminode type categorization experiment) This is todetermine if the types are uniformly distributed along thevertical plane of the cocoa tree Similarly the proportionsof marked flowers that dropped in the relationship betweenstaminode type and success of pollination experiment werealso compared to the expected values Thus a deviation inproportions between the obtained and expected results wouldmean that extent of pollination depends on the category ofstaminode-style distance

The flower-stability ratio was then calculated as thepercentage of the initial number of flowers Means were givenas plusmn1 standard error separated by Duncanrsquos test All analyseswere considered at an overall significance level of 119875 = 005

3 Result

The staminode-style distances ranged between 005mm and325mm and based on these measurements the three cat-egories of staminode types were set out (Table 1) Most(560) of the flowers had converging staminodes whilstsplay staminode constituted the least proportion (65)Proportions of the three staminode types were independentof the two varieties hence the results were pooled together

The fruit set of 156 recorded for parallel staminodeswas not significantly different from the 118 for flowers withconverging staminodes but both were significantly higher(119875 lt 005) than those with splay staminodes (Table 1) Thedistribution of the type of staminode was independent of thevertical section of the cocoa tree (Table 2) The proportionsof the various staminode types per vertical section were alsocomparable to the results obtained in the experiment used tocategorize staminode types

The number and rate of unpollinated flowers thatdropped were higher (119875 = 004) in the dry season than inthe wet During the dry season 512 (plusmn354) unpollinatedflowers had a flower-stability ratio of 72 but there were

Table 2 Distribution of staminode types along the vertical plane ofcocoa tree

Trunk heightabove soil (m)

Type of staminode ()Converging Parallel Splay

03ndash13 566 375 5913ndash23 570 360 7023ndash33 559 380 61

no unpollinated flowers on the tree after the third day(Table 3) On the other hand unpollinated flowers in the wetseason had a flower-stability ratio of 94 on the second dayThis however was reduced to 45 by the third day Dailyobservations of the mature buds during the studies indicatedthat mature buds were completely opened between 0500 and0700 hrs

Generally the number of senescent flowers (ie polli-nated flowers that remained stable on the trees) was signif-icantly higher (119875 = 0001) both during the dry and thewet seasons Pollinated flowers had a 65 stability ratio onthe third day in the dry season whereas the ratio was 95even on the fifth day in the wet season (Table 3) All thepollinated flowers were intact on the trees during the five daysof observation in the wet season except a few flowers that is15 (plusmn25) while pollinated flowers dropped after 4 days in thedry season

4 Discussion

Two key factors that determine the success of fertilizationof cocoa flowers after pollination are effective deposition ofpollen balls (an aggregate or cluster of pollen grains) andpollen compatibility Successful pollination of cocoa requiresthe smearing of pollen balls on the style andor stigmaof a receptive flower [9] A minimum of 35 compatiblepollen grains are required for successful fertilization [2223] Ceratopogonid midges are generally deemed the majorcocoa pollinators worldwide but their efficiency dependson their body sizes which generally ranges from lt1mm togt3mm Species lt2mm were inefficient because their thoraxusually fails to touch the style as the insect crawls along theinner surface of the staminode [7 24 25] Thus no pollenmay be deposited However when pollen is deposited thequantities smeared on the style are inadequate to initiatefertilization The efficiency of larger midges is also perceivedto be influenced by the arrangement of the staminode relativeto the style [7] The results obtained in this study givecredence to the perception Earlier studies by [26] showedcorrelation between the population of ceratopogonid midgesand fruit set of cocoa

The cocoa tree was found to produce flowers with varyingstaminode-style distances ranging from 005mm to 325mmMost of the flowers produced by the cocoa tree have stamin-odes separated from the style by less than 241mm Thusconverging and parallel staminode types of flowers form themajority and these two were also the most ideal staminode-style arrangements for effective pollination The converging

4 Journal of Botany

Table 3 Floral stability of pollinated and unpollinated cocoa flowers during the dry and wet seasons

Day

Dry season (JanuaryndashMarch) Wet season (MayndashJuly)Pollinated Unpollinated Pollinated Unpollinated

Flower-stability Flower-stability Flower-stability Flower-stabilityRatio () Total Ratio () Total Ratio () Total Ratio () Total

2 100 1110 72 800 100 1110 94 10433 65 7215 0 0 100 1110 45 5004 0 0 0 0 98 1088 5 05 0 0 0 0 95 1054 0 0

staminode flowers were expected to give higher fruit setcompared to the parallel because the smaller staminode-stylegap should offer a more intimate contact between pollinatingmidge and the style Consequentlymore pollen grains shouldbe dislodged from the midgersquos thorax onto the style On thecontrary parallel staminode flowers gave higher fruit setthough not statistically significant It is therefore possiblethat midges prefer landing on parallel staminodes relative toconverging ones and further studies on landing preferencesmust be conducted

Although splay staminode flowers were less efficientlypollinated they constituted very small proportions of thetotal flowers produced by the cocoa tree This implies thata very small proportion of unpollinated splay staminodeflowers did not influence significantly the proportion of suc-cessfully pollinated flowersMoreover aged flowers (about 48hours old) tend to splay their staminodes irrespective of thestaminode type during the receptive phase of the flower [7]It is therefore inferred that cocoa trees mostly produce thetype of flowers that could be effectively pollinated by the rightpollinators during the receptive phase of the flower Cocoaflowers are produced at old axillary buds which tend to swellto form a ldquoflower cushionrdquo after repetitive flowering Theseflower cushions are frequently injured through repeated podharvesting leading to reduced flower production at affectedpoints The even distribution of the three types of staminodeflowers along the vertical plane of cocoa trees indicates thatthe age and nature of the flower cushion do not affect the typeof staminode flowers they produce

The results show that cocoa trees generally droppedtheir flowers when unpollinated a confirmation of a widelyreported phenomenon (eg [17 27]) However this studyhas demonstrated that the loss is greater in the dry seasonswhen humidity is low Unpollinated flowers under the dryconditions could not be found after the second (2nd) day(Table 3) Flowers that dropped in the dry season appeareddry pinkish and reduced in size indicating some waterstress [28] The unpollinated flowers in the wet season wererelatively more stable as they achieved 5 flower-stabilityratio on the fourth (4th) day and some flowers were foundeven on the fifth (5th) day during the wet period The 2to 5 percent loss (flower-stability ratio 98 and 95) ofpollinated flowers on the 4th and 5th days in the wet seasoncould be explained in terms of flower abortion which is acommon feature in angiosperms [1] The observations implythat the stability of cocoa flowers may be influenced by two

major factors seasonal conditions (abiotic) and pollination(biotic)

Findings of this study could have bearing on the dynamicsof cocoa pollination Young [29] had noted that cocoa polli-nation involves harmonization between pollinator popula-tion cycle and the phenology of the flowering cocoa treesThis was further explained by [13] that indicated that thenumbers of cocoa pollinating midges were reduced duringthe dry season but increased in thewet season and attributedit to the habit of the midges which live and breed in a cooland moist environment During the dry season cocoa leaveswhich constituted the bulk of ground mat dried up and thusbecame unsuitable for breeding of midges [13 16] Vaughtonand Ramsey [30] have proposed two possible causes for thegreat loss through flower drops in the dry season reducedrate of pollination resulting from low numbers of pollinatorsand reduced accessibility to nutrients and nutrients uptakeTheir findings confirmed that the massive flower drops thatoccurred in the dry season could have been caused by adwindling pollinator population during the dry season Ithas long been known that tropical forest accumulates plantnutrients in the top few centimeters of soil When suchforest is cleared the nutrients are rapidly released and givethe soil a high fertility for a few years The Amazon cocoawhich is a high yielding variety depletes the soil of itsnutrients at a faster rate [31] Some authors have thereforesuggested that the fastidious clearing of cocoa farms aspertains in some cocoa areas should be discouraged [1532] The relatively higher stability of cocoa flowers in thewet season might be attributed to availability of requisitenutrients of cocoa which need water for effective uptakeand physiological cues inherent in the cocoa trees Duringthe dry season the reduced moisture in the soil might haveaffected the amount of nutrients for the cocoa plant To obtainfunctional balance flowers are abscised The vast number offlowers that abscised might also result from a predispositionof cocoa to limit fruit development as explained aboveConsequently only under the best of circumstances may thenecessary physiological signals be able to override the flowerabortion signal Hasenstein and Zavada [33] had attributedthe abscission process inmature flower buds to reduced auxinlevels This seems to apply to cocoa flowers studied Sinceflower production represents a considerable investment forthe plant [1] the number of flowers could affect the allotmentof auxin for each flower

Journal of Botany 5

5 Conclusion

Flowers of varying staminode-style distances are produced bythe cocoa tree and this has been categorized into convergingparallel and splay staminode flowers Splay staminode flow-ers were the least efficiently pollinated but were a small pro-portion of the total flowers hence they had an insignificanteffect on overall pollination success of the cocoa trees Thestability of cocoa flowers is largely determined by pollinationand seasons Flowers stay longer during the wet period andthis may coincide with high pollinator abundance

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This study was supported by the Department of Entomologyand Wildlife School of Biological Sciences University ofCape Coast Cape Coast and the Teaching and LearningInnovation Fund (TALIF) of World Bank The authors arealso grateful to the cocoa farmers in the study areas of thetwo regions for allowing them to use the cocoa trees on theirfarms

References

[1] A G Stephenson ldquoFlower and fruit abortion proximate causesand ultimate functionsrdquo Annual Review of Ecology and System-atics vol 12 pp 253ndash279 1981

[2] B Pıas and P Guitian ldquoBreeding system and pollen limitationin the masting tree Sorbus aucuparia L (Rosaceae) in the NWIberian Peninsulardquo Acta Oecologica vol 29 no 1 pp 97ndash1032006

[3] A M Young Population Biology of Tropical Insects PlenumPress New York NY USA 1982

[4] AM Young ldquoHabitat differences in cocoa tree flowering fruit-set and pollinator availability in Costa Ricardquo Journal of TropicalEcology vol 2 no 2 pp 163ndash186 1986

[5] E A Frimpong I Gordon P K Kwapong and B Gemmill-Herren ldquoDynamics of cocoa pollination tools and applicationsfor surveying and monitoring cocoa pollinatorsrdquo InternationalJournal of Tropical Insect Science vol 29 no 2 pp 62ndash69 2009

[6] D R Glendinning ldquoNatural pollination of CocoardquoNew Phytol-ogist vol 71 no 4 pp 719ndash729 1972

[7] T Kaufmann ldquoStudies on the ecology and biology of a cocoapollinator Forcipomyia squamipennis I and M (Diptera Cer-atopogonidae) in Ghanardquo Bulleting of Entomological Researchvol 65 pp 263ndash268 1975

[8] T Kaufmann ldquoPreliminary observations on a cecidomyiidmidge and its role as a cocoa pollinator in Ghanardquo GhanaJournal of Agricultural Science vol 6 pp 193ndash198 1973

[9] D B Murray ldquoThe botany of cocoardquo in Cocoa G A R WoodEd pp 7ndash18 Longman London UK 3rd edition 1975

[10] S E McGregor Insect Pollination of Cultivated Crop Plants USDepartment of Agriculture Handbook 1976

[11] A M Young M Schaller and M Strand ldquoFloral nectariesand trichomes in relation to pollination in some species of

Theobroma and Herrania (Sterculiaceae)rdquo American Journal ofBotany vol 71 no 4 pp 466ndash480 1984

[12] T Kaufmann ldquoBehavioural biology of a cocoa pollinator Forci-pormyia inornatipennis (Diptera Ceratopogonidae) in GhanardquoJournal of Kansas Entomological Society vol 47 no 4 pp 541ndash148 1974

[13] A H Brew ldquoStudies on cocoa pollination inGhanardquo in Proceed-ings of 9th Internationational Cocoa Research Conference LomeGuinea 1984

[14] A F Posnette and H M Entwistle ldquoThe Pollination of cocoaflowers Rptrdquo inCocoaConference pp 66ndash69GrosvenorHouseLondon UK September 1958 Plant Breeding vol 28 no 4 pp4550 1958

[15] T Mabbett ldquoMidges the insect key to cocoa pollinationrdquo Cocoaand Coffee International Issue vol 4 article 56 1989

[16] A H Brew and J Boorman ldquoPreliminary observations onthe classification of Forcipomyia midges (Diptera Ceratopogo-nidae) of Ghanawith special reference to species involved in thepollination of cocoa (Theobroma cacao L)rdquo Cafe CacaoThe vol372 pp 139ndash144 1993

[17] M M Bos I Steffan-Dewenter and T Tscharntke ldquoShade treemanagement affects fruit abortion insect pests and pathogensof cacaordquoAgriculture Ecosystems and Environment vol 120 no2-4 pp 201ndash205 2007

[18] J A Winder and P Silva ldquoCacao pollination microdiptera ofcacao plantations and some of their breeding placesrdquo Bulletin ofEntomological Research vol 61 pp 651ndash655 1972

[19] A D McKelvie ldquoA list of mutant genes in Arabidopsis thaliana(L) Heynhrdquo Radiation Botany vol 1 pp 233ndash241 1961

[20] M Falque A Vincent B E Vaissiere and A B Eskes ldquoEffect ofpollination intensity on fruit and seed set in cacao (Theobromacacao L)rdquo Sexual Plant Reproduction vol 8 no 6 pp 354ndash3601995

[21] M M Bos I Steffan-Dewenter and T Tscharntke ldquoShade treemanagement affects fruit abortion insect pests and pathogensof cacaordquoAgriculture Ecosystems and Environment vol 120 no2-4 pp 201ndash205 2007

[22] T Kaufmann ldquoBehavioural biology of a cocoa pollinator Forci-pomyia squampipannis (Diptera Ceratopogonidae) in GhanardquoJournal of the Kansas Entomological Society vol 47 pp 541ndash5481974

[23] T Kaufmann ldquoStudies on the ecology and biology of cocoapollinator Forcipomyia squampipannis (Diptera Ceratopogo-nidae) in Ghanardquo Bulletin of Entomological Research vol 65pp 263ndash268 1975

[24] T Kaufmann ldquoEcology and behaviour of cocoa pollinatingCeratopogonidae in Ghana West Africardquo Environmental Ento-mology vol 4 no 2 pp 347ndash351 1975

[25] A M Young ldquoEffects of shade cover and availability of midgebreeding sites on pollination midge populations and fruit set intwo cocoa farmsrdquo Journal of Applied Ecology vol 19 no 1 pp47ndash63 1982

[26] E A Frimpong B Gemmill-Herren I Gordon and P K Kwa-pong ldquoDynamics of insect pollinators as influenced by CocoaProduction systems in Ghanardquo Journal of Pollination Ecologyvol 5 no 10 pp 74ndash80 2011

[27] M Aneja T Gianfagna and E Ng ldquoThe roles of abscisic acidand ethylene in the abscission and senescence of cocoa flowersrdquoPlant Growth Regulation vol 27 no 3 pp 149ndash155 1999

[28] M K Adjaloo W Oduro and B K Banful ldquoFloral phenologyof Upper Amazon Cocoa trees implications for reproduction

6 Journal of Botany

and productivity of Cocoardquo International Scholarly ResearchNetwork (ISRN)Agronomy vol 2012 Article ID 461674 8 pages2012

[29] A M Young ldquoSeasonal differences in abundance and distri-bution of cocoa- pollinating midges in relation to floweringand fruit set between shaded and sunny habitats of the La LolaCocoa Farm in Costa Ricardquo Journal of Applied Ecology vol 20no 3 pp 801ndash831 1983

[30] G Vaughton andM Ramsey ldquoPollinators and seed productionrdquoin Seed Development and Germination J Kigel and G GaliliEds pp 475ndash490 Marcel Dekker NewYork NY USA 1995

[31] G J Anim-Kwapong K Opoku-Ameyaw F M Amoah et alCocoa Agronomy AReview Cocoa Research Insitute of GhanaNew Tafo-Akim Koforidua

[32] J A Winder ldquoCocoa flower Diptera their identity pollinatingactivity and breeding sitesrdquo PAN vol 24 pp 5ndash18 1978

[33] K H Hasenstein and M S Zavada ldquoAuxin modification ofthe incompatibility response in Theobroma cacaordquo PhysiologiaPlantarum vol 112 no 1 pp 113ndash118 2001

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Microbiology

2 Journal of Botany

(a) Converging (b) Parallel (c) Splay

Figure 1 Cocoa flowers showing different staminode (arrowed) arrangement

maximum pollination is necessary for optimum yieldrdquo [15]It is therefore essential to acquire sound knowledge of thepollination ecology of cocoa which has been largely ignoredover the years [16 17] Winder and Silva [18] have observedthat in order to enhance knowledge on natural pollinationand hence the crop yield the characteristics of the cocoa treeand its flowersmust be consideredThis calls for some studiesof floral phenology of cocoa trees as well as flower persistenceand stability

This study therefore evaluated the staminode-style dis-tance in relation to fruit set of cocoa and the distribution ofthe different types of staminode-style arrangements along thevertical plane of the cocoa tree In addition the stability of thecocoa flowers under the dry and wet seasons was assessed todetermine their response to pollination

2 Methodology

21 Study Site The study was conducted from 2009 to2010 in two cocoa farms (N05∘194101015840 W001∘242111015840 andN05∘195161015840 W001∘241071015840) at Abrafo in the Twifo HemangLower Denkyira of the Central Region of Ghana togetherwith ten cocoa farms (6∘401015840364s N and 1∘211015840445s W)located at various distances to the Bobiri Forest Reserve atKubease in the Ejisu-Juaben District Ashanti Region All thefarms hadmixtures of hybrid and Upper Amazon varieties of15ndash25-year-old trees Each farm was divided into 4 quadrants(plots) each measuring 12 plusmn 02SD acres

22 Categorisation of Staminode-Style Distance A total of600 cocoa flowers (approximately 75 per plot) were randomlypicked from the trees together with fresh flowers that haddropped to the ground The flowers were put into glass jarswith moistened cotton wool at the base to prevent themfrom withering Distances between the style and 2 randomlyselected staminodes were measured in the laboratory undera stereomicroscope for each flower and the mean (plusmnSD) dis-tance between the staminode and stylewas determined Peaksand troughs of a distribution curve obtained by plottingmeanstaminode-style distance and their frequencies were used todetermine intervals for various flower categories Based onthese the flowers were categorized to three staminode typesconverging parallel and splay (Table 1 and Figure 1)

Table 1 Categorized staminode-style distance and percent fruit set

Type ofstaminoderelative tostyle

Style-staminodedistance (mm)

Per staminodetype Fruit setlowast

Converging le120 560 118a

Parallel 121ndash240 375 156a

Splay ge241 65 05blowastThe fruit set with the same letters is not significantly different

23 Distribution of Staminode Types along the Vertical Planeof Cocoa Trees Eight cocoa trees were randomly selectedfrom each plot and 3 vertical sections of the trunk at heights030ndash130m 131ndash230m and 231ndash330m were marked withpermanent marker Thirty buds which were due to openwithin the next 24 hours within each marked trunk heightwere also marked for each plot Matured buds about toopen can be identified by the prominence of grooves alongjoined edges of sepals where they burst open Buds thatopened about 24 hours after marking were plucked andimmediately put into glass jars with moistened cotton woolat the base Flowers from each trunk section were put indifferent labeled jars Flowers were carefully placed sideways(Figure 1) in the jars and were also spaced out to preventthe staminodes from tangling and subsequent altering oftheir spatial arrangement Staminode-style distances weremeasured as aforementioned in the laboratory This wasrepeated weekly for 6 weeks

24 Relationship between Staminode-Style Distance and Polli-nation Success The staminode type distribution experimentabove was repeated but in this case marked flowers budswere inspected after 72 hours All marked flowers that haddropped to the ground within the period were collectedand their staminode-style distances measured as beforeUnpollinated flowers usually drop off the tree after 48 hours[19] and thus flowers remaining on the tree after the 72-hourperiod were considered pollinated Success of pollination ofeach staminode-style type was estimated indirectly basedon the hypothesis that proportions of flowers that drop(unpollinated) should be comparable to that obtained inthe earlier experiment used to standardized staminode-styledistance categories if their efficiencies are similar

Journal of Botany 3

25 Flower Stability and Pollination A study was carried outduring two dry (JanuaryndashMarch) andwet (MayndashJuly) seasonsto determine the floral stability of cocoa flowers (ie howlong the flowers stayed when unpollinated or pollinated)By a simple random sampling approach one hundred andeleven (111) cocoa trees were selected from ten (10) cocoafarms A total of 555 (five flowers per tree) freshly openedcocoa flowers were randomly sampled from the selectedtrees for the study These flowers were covered with muslincloth to prevent contact with any insect A second set offlowers were selected and manually pollinated following thestandard manual cross-pollination of rubbing three anthersfrom flowers of three different trees against the subjectflowerrsquos stigma ensuring the likelihood of optimal pollination[20 21] A floral census was taken of both pollinated andunpollinated flowers from the second till the fifth day Thewhole process was repeated for each season while observingall exogenous factors that could affect floral stability

26 Data Analysis Chi-square analyses of proportions of thethree staminode-style types at different trunk heights werecompared to the expected proportions (values obtained inthe staminode type categorization experiment) This is todetermine if the types are uniformly distributed along thevertical plane of the cocoa tree Similarly the proportionsof marked flowers that dropped in the relationship betweenstaminode type and success of pollination experiment werealso compared to the expected values Thus a deviation inproportions between the obtained and expected results wouldmean that extent of pollination depends on the category ofstaminode-style distance

The flower-stability ratio was then calculated as thepercentage of the initial number of flowers Means were givenas plusmn1 standard error separated by Duncanrsquos test All analyseswere considered at an overall significance level of 119875 = 005

3 Result

The staminode-style distances ranged between 005mm and325mm and based on these measurements the three cat-egories of staminode types were set out (Table 1) Most(560) of the flowers had converging staminodes whilstsplay staminode constituted the least proportion (65)Proportions of the three staminode types were independentof the two varieties hence the results were pooled together

The fruit set of 156 recorded for parallel staminodeswas not significantly different from the 118 for flowers withconverging staminodes but both were significantly higher(119875 lt 005) than those with splay staminodes (Table 1) Thedistribution of the type of staminode was independent of thevertical section of the cocoa tree (Table 2) The proportionsof the various staminode types per vertical section were alsocomparable to the results obtained in the experiment used tocategorize staminode types

The number and rate of unpollinated flowers thatdropped were higher (119875 = 004) in the dry season than inthe wet During the dry season 512 (plusmn354) unpollinatedflowers had a flower-stability ratio of 72 but there were

Table 2 Distribution of staminode types along the vertical plane ofcocoa tree

Trunk heightabove soil (m)

Type of staminode ()Converging Parallel Splay

03ndash13 566 375 5913ndash23 570 360 7023ndash33 559 380 61

no unpollinated flowers on the tree after the third day(Table 3) On the other hand unpollinated flowers in the wetseason had a flower-stability ratio of 94 on the second dayThis however was reduced to 45 by the third day Dailyobservations of the mature buds during the studies indicatedthat mature buds were completely opened between 0500 and0700 hrs

Generally the number of senescent flowers (ie polli-nated flowers that remained stable on the trees) was signif-icantly higher (119875 = 0001) both during the dry and thewet seasons Pollinated flowers had a 65 stability ratio onthe third day in the dry season whereas the ratio was 95even on the fifth day in the wet season (Table 3) All thepollinated flowers were intact on the trees during the five daysof observation in the wet season except a few flowers that is15 (plusmn25) while pollinated flowers dropped after 4 days in thedry season

4 Discussion

Two key factors that determine the success of fertilizationof cocoa flowers after pollination are effective deposition ofpollen balls (an aggregate or cluster of pollen grains) andpollen compatibility Successful pollination of cocoa requiresthe smearing of pollen balls on the style andor stigmaof a receptive flower [9] A minimum of 35 compatiblepollen grains are required for successful fertilization [2223] Ceratopogonid midges are generally deemed the majorcocoa pollinators worldwide but their efficiency dependson their body sizes which generally ranges from lt1mm togt3mm Species lt2mm were inefficient because their thoraxusually fails to touch the style as the insect crawls along theinner surface of the staminode [7 24 25] Thus no pollenmay be deposited However when pollen is deposited thequantities smeared on the style are inadequate to initiatefertilization The efficiency of larger midges is also perceivedto be influenced by the arrangement of the staminode relativeto the style [7] The results obtained in this study givecredence to the perception Earlier studies by [26] showedcorrelation between the population of ceratopogonid midgesand fruit set of cocoa

The cocoa tree was found to produce flowers with varyingstaminode-style distances ranging from 005mm to 325mmMost of the flowers produced by the cocoa tree have stamin-odes separated from the style by less than 241mm Thusconverging and parallel staminode types of flowers form themajority and these two were also the most ideal staminode-style arrangements for effective pollination The converging

4 Journal of Botany

Table 3 Floral stability of pollinated and unpollinated cocoa flowers during the dry and wet seasons

Day

Dry season (JanuaryndashMarch) Wet season (MayndashJuly)Pollinated Unpollinated Pollinated Unpollinated

Flower-stability Flower-stability Flower-stability Flower-stabilityRatio () Total Ratio () Total Ratio () Total Ratio () Total

2 100 1110 72 800 100 1110 94 10433 65 7215 0 0 100 1110 45 5004 0 0 0 0 98 1088 5 05 0 0 0 0 95 1054 0 0

staminode flowers were expected to give higher fruit setcompared to the parallel because the smaller staminode-stylegap should offer a more intimate contact between pollinatingmidge and the style Consequentlymore pollen grains shouldbe dislodged from the midgersquos thorax onto the style On thecontrary parallel staminode flowers gave higher fruit setthough not statistically significant It is therefore possiblethat midges prefer landing on parallel staminodes relative toconverging ones and further studies on landing preferencesmust be conducted

Although splay staminode flowers were less efficientlypollinated they constituted very small proportions of thetotal flowers produced by the cocoa tree This implies thata very small proportion of unpollinated splay staminodeflowers did not influence significantly the proportion of suc-cessfully pollinated flowersMoreover aged flowers (about 48hours old) tend to splay their staminodes irrespective of thestaminode type during the receptive phase of the flower [7]It is therefore inferred that cocoa trees mostly produce thetype of flowers that could be effectively pollinated by the rightpollinators during the receptive phase of the flower Cocoaflowers are produced at old axillary buds which tend to swellto form a ldquoflower cushionrdquo after repetitive flowering Theseflower cushions are frequently injured through repeated podharvesting leading to reduced flower production at affectedpoints The even distribution of the three types of staminodeflowers along the vertical plane of cocoa trees indicates thatthe age and nature of the flower cushion do not affect the typeof staminode flowers they produce

The results show that cocoa trees generally droppedtheir flowers when unpollinated a confirmation of a widelyreported phenomenon (eg [17 27]) However this studyhas demonstrated that the loss is greater in the dry seasonswhen humidity is low Unpollinated flowers under the dryconditions could not be found after the second (2nd) day(Table 3) Flowers that dropped in the dry season appeareddry pinkish and reduced in size indicating some waterstress [28] The unpollinated flowers in the wet season wererelatively more stable as they achieved 5 flower-stabilityratio on the fourth (4th) day and some flowers were foundeven on the fifth (5th) day during the wet period The 2to 5 percent loss (flower-stability ratio 98 and 95) ofpollinated flowers on the 4th and 5th days in the wet seasoncould be explained in terms of flower abortion which is acommon feature in angiosperms [1] The observations implythat the stability of cocoa flowers may be influenced by two

major factors seasonal conditions (abiotic) and pollination(biotic)

Findings of this study could have bearing on the dynamicsof cocoa pollination Young [29] had noted that cocoa polli-nation involves harmonization between pollinator popula-tion cycle and the phenology of the flowering cocoa treesThis was further explained by [13] that indicated that thenumbers of cocoa pollinating midges were reduced duringthe dry season but increased in thewet season and attributedit to the habit of the midges which live and breed in a cooland moist environment During the dry season cocoa leaveswhich constituted the bulk of ground mat dried up and thusbecame unsuitable for breeding of midges [13 16] Vaughtonand Ramsey [30] have proposed two possible causes for thegreat loss through flower drops in the dry season reducedrate of pollination resulting from low numbers of pollinatorsand reduced accessibility to nutrients and nutrients uptakeTheir findings confirmed that the massive flower drops thatoccurred in the dry season could have been caused by adwindling pollinator population during the dry season Ithas long been known that tropical forest accumulates plantnutrients in the top few centimeters of soil When suchforest is cleared the nutrients are rapidly released and givethe soil a high fertility for a few years The Amazon cocoawhich is a high yielding variety depletes the soil of itsnutrients at a faster rate [31] Some authors have thereforesuggested that the fastidious clearing of cocoa farms aspertains in some cocoa areas should be discouraged [1532] The relatively higher stability of cocoa flowers in thewet season might be attributed to availability of requisitenutrients of cocoa which need water for effective uptakeand physiological cues inherent in the cocoa trees Duringthe dry season the reduced moisture in the soil might haveaffected the amount of nutrients for the cocoa plant To obtainfunctional balance flowers are abscised The vast number offlowers that abscised might also result from a predispositionof cocoa to limit fruit development as explained aboveConsequently only under the best of circumstances may thenecessary physiological signals be able to override the flowerabortion signal Hasenstein and Zavada [33] had attributedthe abscission process inmature flower buds to reduced auxinlevels This seems to apply to cocoa flowers studied Sinceflower production represents a considerable investment forthe plant [1] the number of flowers could affect the allotmentof auxin for each flower

Journal of Botany 5

5 Conclusion

Flowers of varying staminode-style distances are produced bythe cocoa tree and this has been categorized into convergingparallel and splay staminode flowers Splay staminode flow-ers were the least efficiently pollinated but were a small pro-portion of the total flowers hence they had an insignificanteffect on overall pollination success of the cocoa trees Thestability of cocoa flowers is largely determined by pollinationand seasons Flowers stay longer during the wet period andthis may coincide with high pollinator abundance

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This study was supported by the Department of Entomologyand Wildlife School of Biological Sciences University ofCape Coast Cape Coast and the Teaching and LearningInnovation Fund (TALIF) of World Bank The authors arealso grateful to the cocoa farmers in the study areas of thetwo regions for allowing them to use the cocoa trees on theirfarms

References

[1] A G Stephenson ldquoFlower and fruit abortion proximate causesand ultimate functionsrdquo Annual Review of Ecology and System-atics vol 12 pp 253ndash279 1981

[2] B Pıas and P Guitian ldquoBreeding system and pollen limitationin the masting tree Sorbus aucuparia L (Rosaceae) in the NWIberian Peninsulardquo Acta Oecologica vol 29 no 1 pp 97ndash1032006

[3] A M Young Population Biology of Tropical Insects PlenumPress New York NY USA 1982

[4] AM Young ldquoHabitat differences in cocoa tree flowering fruit-set and pollinator availability in Costa Ricardquo Journal of TropicalEcology vol 2 no 2 pp 163ndash186 1986

[5] E A Frimpong I Gordon P K Kwapong and B Gemmill-Herren ldquoDynamics of cocoa pollination tools and applicationsfor surveying and monitoring cocoa pollinatorsrdquo InternationalJournal of Tropical Insect Science vol 29 no 2 pp 62ndash69 2009

[6] D R Glendinning ldquoNatural pollination of CocoardquoNew Phytol-ogist vol 71 no 4 pp 719ndash729 1972

[7] T Kaufmann ldquoStudies on the ecology and biology of a cocoapollinator Forcipomyia squamipennis I and M (Diptera Cer-atopogonidae) in Ghanardquo Bulleting of Entomological Researchvol 65 pp 263ndash268 1975

[8] T Kaufmann ldquoPreliminary observations on a cecidomyiidmidge and its role as a cocoa pollinator in Ghanardquo GhanaJournal of Agricultural Science vol 6 pp 193ndash198 1973

[9] D B Murray ldquoThe botany of cocoardquo in Cocoa G A R WoodEd pp 7ndash18 Longman London UK 3rd edition 1975

[10] S E McGregor Insect Pollination of Cultivated Crop Plants USDepartment of Agriculture Handbook 1976

[11] A M Young M Schaller and M Strand ldquoFloral nectariesand trichomes in relation to pollination in some species of

Theobroma and Herrania (Sterculiaceae)rdquo American Journal ofBotany vol 71 no 4 pp 466ndash480 1984

[12] T Kaufmann ldquoBehavioural biology of a cocoa pollinator Forci-pormyia inornatipennis (Diptera Ceratopogonidae) in GhanardquoJournal of Kansas Entomological Society vol 47 no 4 pp 541ndash148 1974

[13] A H Brew ldquoStudies on cocoa pollination inGhanardquo in Proceed-ings of 9th Internationational Cocoa Research Conference LomeGuinea 1984

[14] A F Posnette and H M Entwistle ldquoThe Pollination of cocoaflowers Rptrdquo inCocoaConference pp 66ndash69GrosvenorHouseLondon UK September 1958 Plant Breeding vol 28 no 4 pp4550 1958

[15] T Mabbett ldquoMidges the insect key to cocoa pollinationrdquo Cocoaand Coffee International Issue vol 4 article 56 1989

[16] A H Brew and J Boorman ldquoPreliminary observations onthe classification of Forcipomyia midges (Diptera Ceratopogo-nidae) of Ghanawith special reference to species involved in thepollination of cocoa (Theobroma cacao L)rdquo Cafe CacaoThe vol372 pp 139ndash144 1993

[17] M M Bos I Steffan-Dewenter and T Tscharntke ldquoShade treemanagement affects fruit abortion insect pests and pathogensof cacaordquoAgriculture Ecosystems and Environment vol 120 no2-4 pp 201ndash205 2007

[18] J A Winder and P Silva ldquoCacao pollination microdiptera ofcacao plantations and some of their breeding placesrdquo Bulletin ofEntomological Research vol 61 pp 651ndash655 1972

[19] A D McKelvie ldquoA list of mutant genes in Arabidopsis thaliana(L) Heynhrdquo Radiation Botany vol 1 pp 233ndash241 1961

[20] M Falque A Vincent B E Vaissiere and A B Eskes ldquoEffect ofpollination intensity on fruit and seed set in cacao (Theobromacacao L)rdquo Sexual Plant Reproduction vol 8 no 6 pp 354ndash3601995

[21] M M Bos I Steffan-Dewenter and T Tscharntke ldquoShade treemanagement affects fruit abortion insect pests and pathogensof cacaordquoAgriculture Ecosystems and Environment vol 120 no2-4 pp 201ndash205 2007

[22] T Kaufmann ldquoBehavioural biology of a cocoa pollinator Forci-pomyia squampipannis (Diptera Ceratopogonidae) in GhanardquoJournal of the Kansas Entomological Society vol 47 pp 541ndash5481974

[23] T Kaufmann ldquoStudies on the ecology and biology of cocoapollinator Forcipomyia squampipannis (Diptera Ceratopogo-nidae) in Ghanardquo Bulletin of Entomological Research vol 65pp 263ndash268 1975

[24] T Kaufmann ldquoEcology and behaviour of cocoa pollinatingCeratopogonidae in Ghana West Africardquo Environmental Ento-mology vol 4 no 2 pp 347ndash351 1975

[25] A M Young ldquoEffects of shade cover and availability of midgebreeding sites on pollination midge populations and fruit set intwo cocoa farmsrdquo Journal of Applied Ecology vol 19 no 1 pp47ndash63 1982

[26] E A Frimpong B Gemmill-Herren I Gordon and P K Kwa-pong ldquoDynamics of insect pollinators as influenced by CocoaProduction systems in Ghanardquo Journal of Pollination Ecologyvol 5 no 10 pp 74ndash80 2011

[27] M Aneja T Gianfagna and E Ng ldquoThe roles of abscisic acidand ethylene in the abscission and senescence of cocoa flowersrdquoPlant Growth Regulation vol 27 no 3 pp 149ndash155 1999

[28] M K Adjaloo W Oduro and B K Banful ldquoFloral phenologyof Upper Amazon Cocoa trees implications for reproduction

6 Journal of Botany

and productivity of Cocoardquo International Scholarly ResearchNetwork (ISRN)Agronomy vol 2012 Article ID 461674 8 pages2012

[29] A M Young ldquoSeasonal differences in abundance and distri-bution of cocoa- pollinating midges in relation to floweringand fruit set between shaded and sunny habitats of the La LolaCocoa Farm in Costa Ricardquo Journal of Applied Ecology vol 20no 3 pp 801ndash831 1983

[30] G Vaughton andM Ramsey ldquoPollinators and seed productionrdquoin Seed Development and Germination J Kigel and G GaliliEds pp 475ndash490 Marcel Dekker NewYork NY USA 1995

[31] G J Anim-Kwapong K Opoku-Ameyaw F M Amoah et alCocoa Agronomy AReview Cocoa Research Insitute of GhanaNew Tafo-Akim Koforidua

[32] J A Winder ldquoCocoa flower Diptera their identity pollinatingactivity and breeding sitesrdquo PAN vol 24 pp 5ndash18 1978

[33] K H Hasenstein and M S Zavada ldquoAuxin modification ofthe incompatibility response in Theobroma cacaordquo PhysiologiaPlantarum vol 112 no 1 pp 113ndash118 2001

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology

Journal of Botany 3

25 Flower Stability and Pollination A study was carried outduring two dry (JanuaryndashMarch) andwet (MayndashJuly) seasonsto determine the floral stability of cocoa flowers (ie howlong the flowers stayed when unpollinated or pollinated)By a simple random sampling approach one hundred andeleven (111) cocoa trees were selected from ten (10) cocoafarms A total of 555 (five flowers per tree) freshly openedcocoa flowers were randomly sampled from the selectedtrees for the study These flowers were covered with muslincloth to prevent contact with any insect A second set offlowers were selected and manually pollinated following thestandard manual cross-pollination of rubbing three anthersfrom flowers of three different trees against the subjectflowerrsquos stigma ensuring the likelihood of optimal pollination[20 21] A floral census was taken of both pollinated andunpollinated flowers from the second till the fifth day Thewhole process was repeated for each season while observingall exogenous factors that could affect floral stability

26 Data Analysis Chi-square analyses of proportions of thethree staminode-style types at different trunk heights werecompared to the expected proportions (values obtained inthe staminode type categorization experiment) This is todetermine if the types are uniformly distributed along thevertical plane of the cocoa tree Similarly the proportionsof marked flowers that dropped in the relationship betweenstaminode type and success of pollination experiment werealso compared to the expected values Thus a deviation inproportions between the obtained and expected results wouldmean that extent of pollination depends on the category ofstaminode-style distance

The flower-stability ratio was then calculated as thepercentage of the initial number of flowers Means were givenas plusmn1 standard error separated by Duncanrsquos test All analyseswere considered at an overall significance level of 119875 = 005

3 Result

The staminode-style distances ranged between 005mm and325mm and based on these measurements the three cat-egories of staminode types were set out (Table 1) Most(560) of the flowers had converging staminodes whilstsplay staminode constituted the least proportion (65)Proportions of the three staminode types were independentof the two varieties hence the results were pooled together

The fruit set of 156 recorded for parallel staminodeswas not significantly different from the 118 for flowers withconverging staminodes but both were significantly higher(119875 lt 005) than those with splay staminodes (Table 1) Thedistribution of the type of staminode was independent of thevertical section of the cocoa tree (Table 2) The proportionsof the various staminode types per vertical section were alsocomparable to the results obtained in the experiment used tocategorize staminode types

The number and rate of unpollinated flowers thatdropped were higher (119875 = 004) in the dry season than inthe wet During the dry season 512 (plusmn354) unpollinatedflowers had a flower-stability ratio of 72 but there were

Table 2 Distribution of staminode types along the vertical plane ofcocoa tree

Trunk heightabove soil (m)

Type of staminode ()Converging Parallel Splay

03ndash13 566 375 5913ndash23 570 360 7023ndash33 559 380 61

no unpollinated flowers on the tree after the third day(Table 3) On the other hand unpollinated flowers in the wetseason had a flower-stability ratio of 94 on the second dayThis however was reduced to 45 by the third day Dailyobservations of the mature buds during the studies indicatedthat mature buds were completely opened between 0500 and0700 hrs

Generally the number of senescent flowers (ie polli-nated flowers that remained stable on the trees) was signif-icantly higher (119875 = 0001) both during the dry and thewet seasons Pollinated flowers had a 65 stability ratio onthe third day in the dry season whereas the ratio was 95even on the fifth day in the wet season (Table 3) All thepollinated flowers were intact on the trees during the five daysof observation in the wet season except a few flowers that is15 (plusmn25) while pollinated flowers dropped after 4 days in thedry season

4 Discussion

Two key factors that determine the success of fertilizationof cocoa flowers after pollination are effective deposition ofpollen balls (an aggregate or cluster of pollen grains) andpollen compatibility Successful pollination of cocoa requiresthe smearing of pollen balls on the style andor stigmaof a receptive flower [9] A minimum of 35 compatiblepollen grains are required for successful fertilization [2223] Ceratopogonid midges are generally deemed the majorcocoa pollinators worldwide but their efficiency dependson their body sizes which generally ranges from lt1mm togt3mm Species lt2mm were inefficient because their thoraxusually fails to touch the style as the insect crawls along theinner surface of the staminode [7 24 25] Thus no pollenmay be deposited However when pollen is deposited thequantities smeared on the style are inadequate to initiatefertilization The efficiency of larger midges is also perceivedto be influenced by the arrangement of the staminode relativeto the style [7] The results obtained in this study givecredence to the perception Earlier studies by [26] showedcorrelation between the population of ceratopogonid midgesand fruit set of cocoa

The cocoa tree was found to produce flowers with varyingstaminode-style distances ranging from 005mm to 325mmMost of the flowers produced by the cocoa tree have stamin-odes separated from the style by less than 241mm Thusconverging and parallel staminode types of flowers form themajority and these two were also the most ideal staminode-style arrangements for effective pollination The converging

4 Journal of Botany

Table 3 Floral stability of pollinated and unpollinated cocoa flowers during the dry and wet seasons

Day

Dry season (JanuaryndashMarch) Wet season (MayndashJuly)Pollinated Unpollinated Pollinated Unpollinated

Flower-stability Flower-stability Flower-stability Flower-stabilityRatio () Total Ratio () Total Ratio () Total Ratio () Total

2 100 1110 72 800 100 1110 94 10433 65 7215 0 0 100 1110 45 5004 0 0 0 0 98 1088 5 05 0 0 0 0 95 1054 0 0

staminode flowers were expected to give higher fruit setcompared to the parallel because the smaller staminode-stylegap should offer a more intimate contact between pollinatingmidge and the style Consequentlymore pollen grains shouldbe dislodged from the midgersquos thorax onto the style On thecontrary parallel staminode flowers gave higher fruit setthough not statistically significant It is therefore possiblethat midges prefer landing on parallel staminodes relative toconverging ones and further studies on landing preferencesmust be conducted

Although splay staminode flowers were less efficientlypollinated they constituted very small proportions of thetotal flowers produced by the cocoa tree This implies thata very small proportion of unpollinated splay staminodeflowers did not influence significantly the proportion of suc-cessfully pollinated flowersMoreover aged flowers (about 48hours old) tend to splay their staminodes irrespective of thestaminode type during the receptive phase of the flower [7]It is therefore inferred that cocoa trees mostly produce thetype of flowers that could be effectively pollinated by the rightpollinators during the receptive phase of the flower Cocoaflowers are produced at old axillary buds which tend to swellto form a ldquoflower cushionrdquo after repetitive flowering Theseflower cushions are frequently injured through repeated podharvesting leading to reduced flower production at affectedpoints The even distribution of the three types of staminodeflowers along the vertical plane of cocoa trees indicates thatthe age and nature of the flower cushion do not affect the typeof staminode flowers they produce

The results show that cocoa trees generally droppedtheir flowers when unpollinated a confirmation of a widelyreported phenomenon (eg [17 27]) However this studyhas demonstrated that the loss is greater in the dry seasonswhen humidity is low Unpollinated flowers under the dryconditions could not be found after the second (2nd) day(Table 3) Flowers that dropped in the dry season appeareddry pinkish and reduced in size indicating some waterstress [28] The unpollinated flowers in the wet season wererelatively more stable as they achieved 5 flower-stabilityratio on the fourth (4th) day and some flowers were foundeven on the fifth (5th) day during the wet period The 2to 5 percent loss (flower-stability ratio 98 and 95) ofpollinated flowers on the 4th and 5th days in the wet seasoncould be explained in terms of flower abortion which is acommon feature in angiosperms [1] The observations implythat the stability of cocoa flowers may be influenced by two

major factors seasonal conditions (abiotic) and pollination(biotic)

Findings of this study could have bearing on the dynamicsof cocoa pollination Young [29] had noted that cocoa polli-nation involves harmonization between pollinator popula-tion cycle and the phenology of the flowering cocoa treesThis was further explained by [13] that indicated that thenumbers of cocoa pollinating midges were reduced duringthe dry season but increased in thewet season and attributedit to the habit of the midges which live and breed in a cooland moist environment During the dry season cocoa leaveswhich constituted the bulk of ground mat dried up and thusbecame unsuitable for breeding of midges [13 16] Vaughtonand Ramsey [30] have proposed two possible causes for thegreat loss through flower drops in the dry season reducedrate of pollination resulting from low numbers of pollinatorsand reduced accessibility to nutrients and nutrients uptakeTheir findings confirmed that the massive flower drops thatoccurred in the dry season could have been caused by adwindling pollinator population during the dry season Ithas long been known that tropical forest accumulates plantnutrients in the top few centimeters of soil When suchforest is cleared the nutrients are rapidly released and givethe soil a high fertility for a few years The Amazon cocoawhich is a high yielding variety depletes the soil of itsnutrients at a faster rate [31] Some authors have thereforesuggested that the fastidious clearing of cocoa farms aspertains in some cocoa areas should be discouraged [1532] The relatively higher stability of cocoa flowers in thewet season might be attributed to availability of requisitenutrients of cocoa which need water for effective uptakeand physiological cues inherent in the cocoa trees Duringthe dry season the reduced moisture in the soil might haveaffected the amount of nutrients for the cocoa plant To obtainfunctional balance flowers are abscised The vast number offlowers that abscised might also result from a predispositionof cocoa to limit fruit development as explained aboveConsequently only under the best of circumstances may thenecessary physiological signals be able to override the flowerabortion signal Hasenstein and Zavada [33] had attributedthe abscission process inmature flower buds to reduced auxinlevels This seems to apply to cocoa flowers studied Sinceflower production represents a considerable investment forthe plant [1] the number of flowers could affect the allotmentof auxin for each flower

Journal of Botany 5

5 Conclusion

Flowers of varying staminode-style distances are produced bythe cocoa tree and this has been categorized into convergingparallel and splay staminode flowers Splay staminode flow-ers were the least efficiently pollinated but were a small pro-portion of the total flowers hence they had an insignificanteffect on overall pollination success of the cocoa trees Thestability of cocoa flowers is largely determined by pollinationand seasons Flowers stay longer during the wet period andthis may coincide with high pollinator abundance

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This study was supported by the Department of Entomologyand Wildlife School of Biological Sciences University ofCape Coast Cape Coast and the Teaching and LearningInnovation Fund (TALIF) of World Bank The authors arealso grateful to the cocoa farmers in the study areas of thetwo regions for allowing them to use the cocoa trees on theirfarms

References

[1] A G Stephenson ldquoFlower and fruit abortion proximate causesand ultimate functionsrdquo Annual Review of Ecology and System-atics vol 12 pp 253ndash279 1981

[2] B Pıas and P Guitian ldquoBreeding system and pollen limitationin the masting tree Sorbus aucuparia L (Rosaceae) in the NWIberian Peninsulardquo Acta Oecologica vol 29 no 1 pp 97ndash1032006

[3] A M Young Population Biology of Tropical Insects PlenumPress New York NY USA 1982

[4] AM Young ldquoHabitat differences in cocoa tree flowering fruit-set and pollinator availability in Costa Ricardquo Journal of TropicalEcology vol 2 no 2 pp 163ndash186 1986

[5] E A Frimpong I Gordon P K Kwapong and B Gemmill-Herren ldquoDynamics of cocoa pollination tools and applicationsfor surveying and monitoring cocoa pollinatorsrdquo InternationalJournal of Tropical Insect Science vol 29 no 2 pp 62ndash69 2009

[6] D R Glendinning ldquoNatural pollination of CocoardquoNew Phytol-ogist vol 71 no 4 pp 719ndash729 1972

[7] T Kaufmann ldquoStudies on the ecology and biology of a cocoapollinator Forcipomyia squamipennis I and M (Diptera Cer-atopogonidae) in Ghanardquo Bulleting of Entomological Researchvol 65 pp 263ndash268 1975

[8] T Kaufmann ldquoPreliminary observations on a cecidomyiidmidge and its role as a cocoa pollinator in Ghanardquo GhanaJournal of Agricultural Science vol 6 pp 193ndash198 1973

[9] D B Murray ldquoThe botany of cocoardquo in Cocoa G A R WoodEd pp 7ndash18 Longman London UK 3rd edition 1975

[10] S E McGregor Insect Pollination of Cultivated Crop Plants USDepartment of Agriculture Handbook 1976

[11] A M Young M Schaller and M Strand ldquoFloral nectariesand trichomes in relation to pollination in some species of

Theobroma and Herrania (Sterculiaceae)rdquo American Journal ofBotany vol 71 no 4 pp 466ndash480 1984

[12] T Kaufmann ldquoBehavioural biology of a cocoa pollinator Forci-pormyia inornatipennis (Diptera Ceratopogonidae) in GhanardquoJournal of Kansas Entomological Society vol 47 no 4 pp 541ndash148 1974

[13] A H Brew ldquoStudies on cocoa pollination inGhanardquo in Proceed-ings of 9th Internationational Cocoa Research Conference LomeGuinea 1984

[14] A F Posnette and H M Entwistle ldquoThe Pollination of cocoaflowers Rptrdquo inCocoaConference pp 66ndash69GrosvenorHouseLondon UK September 1958 Plant Breeding vol 28 no 4 pp4550 1958

[15] T Mabbett ldquoMidges the insect key to cocoa pollinationrdquo Cocoaand Coffee International Issue vol 4 article 56 1989

[16] A H Brew and J Boorman ldquoPreliminary observations onthe classification of Forcipomyia midges (Diptera Ceratopogo-nidae) of Ghanawith special reference to species involved in thepollination of cocoa (Theobroma cacao L)rdquo Cafe CacaoThe vol372 pp 139ndash144 1993

[17] M M Bos I Steffan-Dewenter and T Tscharntke ldquoShade treemanagement affects fruit abortion insect pests and pathogensof cacaordquoAgriculture Ecosystems and Environment vol 120 no2-4 pp 201ndash205 2007

[18] J A Winder and P Silva ldquoCacao pollination microdiptera ofcacao plantations and some of their breeding placesrdquo Bulletin ofEntomological Research vol 61 pp 651ndash655 1972

[19] A D McKelvie ldquoA list of mutant genes in Arabidopsis thaliana(L) Heynhrdquo Radiation Botany vol 1 pp 233ndash241 1961

[20] M Falque A Vincent B E Vaissiere and A B Eskes ldquoEffect ofpollination intensity on fruit and seed set in cacao (Theobromacacao L)rdquo Sexual Plant Reproduction vol 8 no 6 pp 354ndash3601995

[21] M M Bos I Steffan-Dewenter and T Tscharntke ldquoShade treemanagement affects fruit abortion insect pests and pathogensof cacaordquoAgriculture Ecosystems and Environment vol 120 no2-4 pp 201ndash205 2007

[22] T Kaufmann ldquoBehavioural biology of a cocoa pollinator Forci-pomyia squampipannis (Diptera Ceratopogonidae) in GhanardquoJournal of the Kansas Entomological Society vol 47 pp 541ndash5481974

[23] T Kaufmann ldquoStudies on the ecology and biology of cocoapollinator Forcipomyia squampipannis (Diptera Ceratopogo-nidae) in Ghanardquo Bulletin of Entomological Research vol 65pp 263ndash268 1975

[24] T Kaufmann ldquoEcology and behaviour of cocoa pollinatingCeratopogonidae in Ghana West Africardquo Environmental Ento-mology vol 4 no 2 pp 347ndash351 1975

[25] A M Young ldquoEffects of shade cover and availability of midgebreeding sites on pollination midge populations and fruit set intwo cocoa farmsrdquo Journal of Applied Ecology vol 19 no 1 pp47ndash63 1982

[26] E A Frimpong B Gemmill-Herren I Gordon and P K Kwa-pong ldquoDynamics of insect pollinators as influenced by CocoaProduction systems in Ghanardquo Journal of Pollination Ecologyvol 5 no 10 pp 74ndash80 2011

[27] M Aneja T Gianfagna and E Ng ldquoThe roles of abscisic acidand ethylene in the abscission and senescence of cocoa flowersrdquoPlant Growth Regulation vol 27 no 3 pp 149ndash155 1999

[28] M K Adjaloo W Oduro and B K Banful ldquoFloral phenologyof Upper Amazon Cocoa trees implications for reproduction

6 Journal of Botany

and productivity of Cocoardquo International Scholarly ResearchNetwork (ISRN)Agronomy vol 2012 Article ID 461674 8 pages2012

[29] A M Young ldquoSeasonal differences in abundance and distri-bution of cocoa- pollinating midges in relation to floweringand fruit set between shaded and sunny habitats of the La LolaCocoa Farm in Costa Ricardquo Journal of Applied Ecology vol 20no 3 pp 801ndash831 1983

[30] G Vaughton andM Ramsey ldquoPollinators and seed productionrdquoin Seed Development and Germination J Kigel and G GaliliEds pp 475ndash490 Marcel Dekker NewYork NY USA 1995

[31] G J Anim-Kwapong K Opoku-Ameyaw F M Amoah et alCocoa Agronomy AReview Cocoa Research Insitute of GhanaNew Tafo-Akim Koforidua

[32] J A Winder ldquoCocoa flower Diptera their identity pollinatingactivity and breeding sitesrdquo PAN vol 24 pp 5ndash18 1978

[33] K H Hasenstein and M S Zavada ldquoAuxin modification ofthe incompatibility response in Theobroma cacaordquo PhysiologiaPlantarum vol 112 no 1 pp 113ndash118 2001

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology

4 Journal of Botany

Table 3 Floral stability of pollinated and unpollinated cocoa flowers during the dry and wet seasons

Day

Dry season (JanuaryndashMarch) Wet season (MayndashJuly)Pollinated Unpollinated Pollinated Unpollinated

Flower-stability Flower-stability Flower-stability Flower-stabilityRatio () Total Ratio () Total Ratio () Total Ratio () Total

2 100 1110 72 800 100 1110 94 10433 65 7215 0 0 100 1110 45 5004 0 0 0 0 98 1088 5 05 0 0 0 0 95 1054 0 0

staminode flowers were expected to give higher fruit setcompared to the parallel because the smaller staminode-stylegap should offer a more intimate contact between pollinatingmidge and the style Consequentlymore pollen grains shouldbe dislodged from the midgersquos thorax onto the style On thecontrary parallel staminode flowers gave higher fruit setthough not statistically significant It is therefore possiblethat midges prefer landing on parallel staminodes relative toconverging ones and further studies on landing preferencesmust be conducted

Although splay staminode flowers were less efficientlypollinated they constituted very small proportions of thetotal flowers produced by the cocoa tree This implies thata very small proportion of unpollinated splay staminodeflowers did not influence significantly the proportion of suc-cessfully pollinated flowersMoreover aged flowers (about 48hours old) tend to splay their staminodes irrespective of thestaminode type during the receptive phase of the flower [7]It is therefore inferred that cocoa trees mostly produce thetype of flowers that could be effectively pollinated by the rightpollinators during the receptive phase of the flower Cocoaflowers are produced at old axillary buds which tend to swellto form a ldquoflower cushionrdquo after repetitive flowering Theseflower cushions are frequently injured through repeated podharvesting leading to reduced flower production at affectedpoints The even distribution of the three types of staminodeflowers along the vertical plane of cocoa trees indicates thatthe age and nature of the flower cushion do not affect the typeof staminode flowers they produce

The results show that cocoa trees generally droppedtheir flowers when unpollinated a confirmation of a widelyreported phenomenon (eg [17 27]) However this studyhas demonstrated that the loss is greater in the dry seasonswhen humidity is low Unpollinated flowers under the dryconditions could not be found after the second (2nd) day(Table 3) Flowers that dropped in the dry season appeareddry pinkish and reduced in size indicating some waterstress [28] The unpollinated flowers in the wet season wererelatively more stable as they achieved 5 flower-stabilityratio on the fourth (4th) day and some flowers were foundeven on the fifth (5th) day during the wet period The 2to 5 percent loss (flower-stability ratio 98 and 95) ofpollinated flowers on the 4th and 5th days in the wet seasoncould be explained in terms of flower abortion which is acommon feature in angiosperms [1] The observations implythat the stability of cocoa flowers may be influenced by two

major factors seasonal conditions (abiotic) and pollination(biotic)

Findings of this study could have bearing on the dynamicsof cocoa pollination Young [29] had noted that cocoa polli-nation involves harmonization between pollinator popula-tion cycle and the phenology of the flowering cocoa treesThis was further explained by [13] that indicated that thenumbers of cocoa pollinating midges were reduced duringthe dry season but increased in thewet season and attributedit to the habit of the midges which live and breed in a cooland moist environment During the dry season cocoa leaveswhich constituted the bulk of ground mat dried up and thusbecame unsuitable for breeding of midges [13 16] Vaughtonand Ramsey [30] have proposed two possible causes for thegreat loss through flower drops in the dry season reducedrate of pollination resulting from low numbers of pollinatorsand reduced accessibility to nutrients and nutrients uptakeTheir findings confirmed that the massive flower drops thatoccurred in the dry season could have been caused by adwindling pollinator population during the dry season Ithas long been known that tropical forest accumulates plantnutrients in the top few centimeters of soil When suchforest is cleared the nutrients are rapidly released and givethe soil a high fertility for a few years The Amazon cocoawhich is a high yielding variety depletes the soil of itsnutrients at a faster rate [31] Some authors have thereforesuggested that the fastidious clearing of cocoa farms aspertains in some cocoa areas should be discouraged [1532] The relatively higher stability of cocoa flowers in thewet season might be attributed to availability of requisitenutrients of cocoa which need water for effective uptakeand physiological cues inherent in the cocoa trees Duringthe dry season the reduced moisture in the soil might haveaffected the amount of nutrients for the cocoa plant To obtainfunctional balance flowers are abscised The vast number offlowers that abscised might also result from a predispositionof cocoa to limit fruit development as explained aboveConsequently only under the best of circumstances may thenecessary physiological signals be able to override the flowerabortion signal Hasenstein and Zavada [33] had attributedthe abscission process inmature flower buds to reduced auxinlevels This seems to apply to cocoa flowers studied Sinceflower production represents a considerable investment forthe plant [1] the number of flowers could affect the allotmentof auxin for each flower

Journal of Botany 5

5 Conclusion

Flowers of varying staminode-style distances are produced bythe cocoa tree and this has been categorized into convergingparallel and splay staminode flowers Splay staminode flow-ers were the least efficiently pollinated but were a small pro-portion of the total flowers hence they had an insignificanteffect on overall pollination success of the cocoa trees Thestability of cocoa flowers is largely determined by pollinationand seasons Flowers stay longer during the wet period andthis may coincide with high pollinator abundance

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This study was supported by the Department of Entomologyand Wildlife School of Biological Sciences University ofCape Coast Cape Coast and the Teaching and LearningInnovation Fund (TALIF) of World Bank The authors arealso grateful to the cocoa farmers in the study areas of thetwo regions for allowing them to use the cocoa trees on theirfarms

References

[1] A G Stephenson ldquoFlower and fruit abortion proximate causesand ultimate functionsrdquo Annual Review of Ecology and System-atics vol 12 pp 253ndash279 1981

[2] B Pıas and P Guitian ldquoBreeding system and pollen limitationin the masting tree Sorbus aucuparia L (Rosaceae) in the NWIberian Peninsulardquo Acta Oecologica vol 29 no 1 pp 97ndash1032006

[3] A M Young Population Biology of Tropical Insects PlenumPress New York NY USA 1982

[4] AM Young ldquoHabitat differences in cocoa tree flowering fruit-set and pollinator availability in Costa Ricardquo Journal of TropicalEcology vol 2 no 2 pp 163ndash186 1986

[5] E A Frimpong I Gordon P K Kwapong and B Gemmill-Herren ldquoDynamics of cocoa pollination tools and applicationsfor surveying and monitoring cocoa pollinatorsrdquo InternationalJournal of Tropical Insect Science vol 29 no 2 pp 62ndash69 2009

[6] D R Glendinning ldquoNatural pollination of CocoardquoNew Phytol-ogist vol 71 no 4 pp 719ndash729 1972

[7] T Kaufmann ldquoStudies on the ecology and biology of a cocoapollinator Forcipomyia squamipennis I and M (Diptera Cer-atopogonidae) in Ghanardquo Bulleting of Entomological Researchvol 65 pp 263ndash268 1975

[8] T Kaufmann ldquoPreliminary observations on a cecidomyiidmidge and its role as a cocoa pollinator in Ghanardquo GhanaJournal of Agricultural Science vol 6 pp 193ndash198 1973

[9] D B Murray ldquoThe botany of cocoardquo in Cocoa G A R WoodEd pp 7ndash18 Longman London UK 3rd edition 1975

[10] S E McGregor Insect Pollination of Cultivated Crop Plants USDepartment of Agriculture Handbook 1976

[11] A M Young M Schaller and M Strand ldquoFloral nectariesand trichomes in relation to pollination in some species of

Theobroma and Herrania (Sterculiaceae)rdquo American Journal ofBotany vol 71 no 4 pp 466ndash480 1984

[12] T Kaufmann ldquoBehavioural biology of a cocoa pollinator Forci-pormyia inornatipennis (Diptera Ceratopogonidae) in GhanardquoJournal of Kansas Entomological Society vol 47 no 4 pp 541ndash148 1974

[13] A H Brew ldquoStudies on cocoa pollination inGhanardquo in Proceed-ings of 9th Internationational Cocoa Research Conference LomeGuinea 1984

[14] A F Posnette and H M Entwistle ldquoThe Pollination of cocoaflowers Rptrdquo inCocoaConference pp 66ndash69GrosvenorHouseLondon UK September 1958 Plant Breeding vol 28 no 4 pp4550 1958

[15] T Mabbett ldquoMidges the insect key to cocoa pollinationrdquo Cocoaand Coffee International Issue vol 4 article 56 1989

[16] A H Brew and J Boorman ldquoPreliminary observations onthe classification of Forcipomyia midges (Diptera Ceratopogo-nidae) of Ghanawith special reference to species involved in thepollination of cocoa (Theobroma cacao L)rdquo Cafe CacaoThe vol372 pp 139ndash144 1993

[17] M M Bos I Steffan-Dewenter and T Tscharntke ldquoShade treemanagement affects fruit abortion insect pests and pathogensof cacaordquoAgriculture Ecosystems and Environment vol 120 no2-4 pp 201ndash205 2007

[18] J A Winder and P Silva ldquoCacao pollination microdiptera ofcacao plantations and some of their breeding placesrdquo Bulletin ofEntomological Research vol 61 pp 651ndash655 1972

[19] A D McKelvie ldquoA list of mutant genes in Arabidopsis thaliana(L) Heynhrdquo Radiation Botany vol 1 pp 233ndash241 1961

[20] M Falque A Vincent B E Vaissiere and A B Eskes ldquoEffect ofpollination intensity on fruit and seed set in cacao (Theobromacacao L)rdquo Sexual Plant Reproduction vol 8 no 6 pp 354ndash3601995

[21] M M Bos I Steffan-Dewenter and T Tscharntke ldquoShade treemanagement affects fruit abortion insect pests and pathogensof cacaordquoAgriculture Ecosystems and Environment vol 120 no2-4 pp 201ndash205 2007

[22] T Kaufmann ldquoBehavioural biology of a cocoa pollinator Forci-pomyia squampipannis (Diptera Ceratopogonidae) in GhanardquoJournal of the Kansas Entomological Society vol 47 pp 541ndash5481974

[23] T Kaufmann ldquoStudies on the ecology and biology of cocoapollinator Forcipomyia squampipannis (Diptera Ceratopogo-nidae) in Ghanardquo Bulletin of Entomological Research vol 65pp 263ndash268 1975

[24] T Kaufmann ldquoEcology and behaviour of cocoa pollinatingCeratopogonidae in Ghana West Africardquo Environmental Ento-mology vol 4 no 2 pp 347ndash351 1975

[25] A M Young ldquoEffects of shade cover and availability of midgebreeding sites on pollination midge populations and fruit set intwo cocoa farmsrdquo Journal of Applied Ecology vol 19 no 1 pp47ndash63 1982

[26] E A Frimpong B Gemmill-Herren I Gordon and P K Kwa-pong ldquoDynamics of insect pollinators as influenced by CocoaProduction systems in Ghanardquo Journal of Pollination Ecologyvol 5 no 10 pp 74ndash80 2011

[27] M Aneja T Gianfagna and E Ng ldquoThe roles of abscisic acidand ethylene in the abscission and senescence of cocoa flowersrdquoPlant Growth Regulation vol 27 no 3 pp 149ndash155 1999

[28] M K Adjaloo W Oduro and B K Banful ldquoFloral phenologyof Upper Amazon Cocoa trees implications for reproduction

6 Journal of Botany

and productivity of Cocoardquo International Scholarly ResearchNetwork (ISRN)Agronomy vol 2012 Article ID 461674 8 pages2012

[29] A M Young ldquoSeasonal differences in abundance and distri-bution of cocoa- pollinating midges in relation to floweringand fruit set between shaded and sunny habitats of the La LolaCocoa Farm in Costa Ricardquo Journal of Applied Ecology vol 20no 3 pp 801ndash831 1983

[30] G Vaughton andM Ramsey ldquoPollinators and seed productionrdquoin Seed Development and Germination J Kigel and G GaliliEds pp 475ndash490 Marcel Dekker NewYork NY USA 1995

[31] G J Anim-Kwapong K Opoku-Ameyaw F M Amoah et alCocoa Agronomy AReview Cocoa Research Insitute of GhanaNew Tafo-Akim Koforidua

[32] J A Winder ldquoCocoa flower Diptera their identity pollinatingactivity and breeding sitesrdquo PAN vol 24 pp 5ndash18 1978

[33] K H Hasenstein and M S Zavada ldquoAuxin modification ofthe incompatibility response in Theobroma cacaordquo PhysiologiaPlantarum vol 112 no 1 pp 113ndash118 2001

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology

Journal of Botany 5

5 Conclusion

Flowers of varying staminode-style distances are produced bythe cocoa tree and this has been categorized into convergingparallel and splay staminode flowers Splay staminode flow-ers were the least efficiently pollinated but were a small pro-portion of the total flowers hence they had an insignificanteffect on overall pollination success of the cocoa trees Thestability of cocoa flowers is largely determined by pollinationand seasons Flowers stay longer during the wet period andthis may coincide with high pollinator abundance

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This study was supported by the Department of Entomologyand Wildlife School of Biological Sciences University ofCape Coast Cape Coast and the Teaching and LearningInnovation Fund (TALIF) of World Bank The authors arealso grateful to the cocoa farmers in the study areas of thetwo regions for allowing them to use the cocoa trees on theirfarms

References

[1] A G Stephenson ldquoFlower and fruit abortion proximate causesand ultimate functionsrdquo Annual Review of Ecology and System-atics vol 12 pp 253ndash279 1981

[2] B Pıas and P Guitian ldquoBreeding system and pollen limitationin the masting tree Sorbus aucuparia L (Rosaceae) in the NWIberian Peninsulardquo Acta Oecologica vol 29 no 1 pp 97ndash1032006

[3] A M Young Population Biology of Tropical Insects PlenumPress New York NY USA 1982

[4] AM Young ldquoHabitat differences in cocoa tree flowering fruit-set and pollinator availability in Costa Ricardquo Journal of TropicalEcology vol 2 no 2 pp 163ndash186 1986

[5] E A Frimpong I Gordon P K Kwapong and B Gemmill-Herren ldquoDynamics of cocoa pollination tools and applicationsfor surveying and monitoring cocoa pollinatorsrdquo InternationalJournal of Tropical Insect Science vol 29 no 2 pp 62ndash69 2009

[6] D R Glendinning ldquoNatural pollination of CocoardquoNew Phytol-ogist vol 71 no 4 pp 719ndash729 1972

[7] T Kaufmann ldquoStudies on the ecology and biology of a cocoapollinator Forcipomyia squamipennis I and M (Diptera Cer-atopogonidae) in Ghanardquo Bulleting of Entomological Researchvol 65 pp 263ndash268 1975

[8] T Kaufmann ldquoPreliminary observations on a cecidomyiidmidge and its role as a cocoa pollinator in Ghanardquo GhanaJournal of Agricultural Science vol 6 pp 193ndash198 1973

[9] D B Murray ldquoThe botany of cocoardquo in Cocoa G A R WoodEd pp 7ndash18 Longman London UK 3rd edition 1975

[10] S E McGregor Insect Pollination of Cultivated Crop Plants USDepartment of Agriculture Handbook 1976

[11] A M Young M Schaller and M Strand ldquoFloral nectariesand trichomes in relation to pollination in some species of

Theobroma and Herrania (Sterculiaceae)rdquo American Journal ofBotany vol 71 no 4 pp 466ndash480 1984

[12] T Kaufmann ldquoBehavioural biology of a cocoa pollinator Forci-pormyia inornatipennis (Diptera Ceratopogonidae) in GhanardquoJournal of Kansas Entomological Society vol 47 no 4 pp 541ndash148 1974

[13] A H Brew ldquoStudies on cocoa pollination inGhanardquo in Proceed-ings of 9th Internationational Cocoa Research Conference LomeGuinea 1984

[14] A F Posnette and H M Entwistle ldquoThe Pollination of cocoaflowers Rptrdquo inCocoaConference pp 66ndash69GrosvenorHouseLondon UK September 1958 Plant Breeding vol 28 no 4 pp4550 1958

[15] T Mabbett ldquoMidges the insect key to cocoa pollinationrdquo Cocoaand Coffee International Issue vol 4 article 56 1989

[16] A H Brew and J Boorman ldquoPreliminary observations onthe classification of Forcipomyia midges (Diptera Ceratopogo-nidae) of Ghanawith special reference to species involved in thepollination of cocoa (Theobroma cacao L)rdquo Cafe CacaoThe vol372 pp 139ndash144 1993

[17] M M Bos I Steffan-Dewenter and T Tscharntke ldquoShade treemanagement affects fruit abortion insect pests and pathogensof cacaordquoAgriculture Ecosystems and Environment vol 120 no2-4 pp 201ndash205 2007

[18] J A Winder and P Silva ldquoCacao pollination microdiptera ofcacao plantations and some of their breeding placesrdquo Bulletin ofEntomological Research vol 61 pp 651ndash655 1972

[19] A D McKelvie ldquoA list of mutant genes in Arabidopsis thaliana(L) Heynhrdquo Radiation Botany vol 1 pp 233ndash241 1961

[20] M Falque A Vincent B E Vaissiere and A B Eskes ldquoEffect ofpollination intensity on fruit and seed set in cacao (Theobromacacao L)rdquo Sexual Plant Reproduction vol 8 no 6 pp 354ndash3601995

[21] M M Bos I Steffan-Dewenter and T Tscharntke ldquoShade treemanagement affects fruit abortion insect pests and pathogensof cacaordquoAgriculture Ecosystems and Environment vol 120 no2-4 pp 201ndash205 2007

[22] T Kaufmann ldquoBehavioural biology of a cocoa pollinator Forci-pomyia squampipannis (Diptera Ceratopogonidae) in GhanardquoJournal of the Kansas Entomological Society vol 47 pp 541ndash5481974

[23] T Kaufmann ldquoStudies on the ecology and biology of cocoapollinator Forcipomyia squampipannis (Diptera Ceratopogo-nidae) in Ghanardquo Bulletin of Entomological Research vol 65pp 263ndash268 1975

[24] T Kaufmann ldquoEcology and behaviour of cocoa pollinatingCeratopogonidae in Ghana West Africardquo Environmental Ento-mology vol 4 no 2 pp 347ndash351 1975

[25] A M Young ldquoEffects of shade cover and availability of midgebreeding sites on pollination midge populations and fruit set intwo cocoa farmsrdquo Journal of Applied Ecology vol 19 no 1 pp47ndash63 1982

[26] E A Frimpong B Gemmill-Herren I Gordon and P K Kwa-pong ldquoDynamics of insect pollinators as influenced by CocoaProduction systems in Ghanardquo Journal of Pollination Ecologyvol 5 no 10 pp 74ndash80 2011

[27] M Aneja T Gianfagna and E Ng ldquoThe roles of abscisic acidand ethylene in the abscission and senescence of cocoa flowersrdquoPlant Growth Regulation vol 27 no 3 pp 149ndash155 1999

[28] M K Adjaloo W Oduro and B K Banful ldquoFloral phenologyof Upper Amazon Cocoa trees implications for reproduction

6 Journal of Botany

and productivity of Cocoardquo International Scholarly ResearchNetwork (ISRN)Agronomy vol 2012 Article ID 461674 8 pages2012

[29] A M Young ldquoSeasonal differences in abundance and distri-bution of cocoa- pollinating midges in relation to floweringand fruit set between shaded and sunny habitats of the La LolaCocoa Farm in Costa Ricardquo Journal of Applied Ecology vol 20no 3 pp 801ndash831 1983

[30] G Vaughton andM Ramsey ldquoPollinators and seed productionrdquoin Seed Development and Germination J Kigel and G GaliliEds pp 475ndash490 Marcel Dekker NewYork NY USA 1995

[31] G J Anim-Kwapong K Opoku-Ameyaw F M Amoah et alCocoa Agronomy AReview Cocoa Research Insitute of GhanaNew Tafo-Akim Koforidua

[32] J A Winder ldquoCocoa flower Diptera their identity pollinatingactivity and breeding sitesrdquo PAN vol 24 pp 5ndash18 1978

[33] K H Hasenstein and M S Zavada ldquoAuxin modification ofthe incompatibility response in Theobroma cacaordquo PhysiologiaPlantarum vol 112 no 1 pp 113ndash118 2001

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology

6 Journal of Botany

and productivity of Cocoardquo International Scholarly ResearchNetwork (ISRN)Agronomy vol 2012 Article ID 461674 8 pages2012

[29] A M Young ldquoSeasonal differences in abundance and distri-bution of cocoa- pollinating midges in relation to floweringand fruit set between shaded and sunny habitats of the La LolaCocoa Farm in Costa Ricardquo Journal of Applied Ecology vol 20no 3 pp 801ndash831 1983

[30] G Vaughton andM Ramsey ldquoPollinators and seed productionrdquoin Seed Development and Germination J Kigel and G GaliliEds pp 475ndash490 Marcel Dekker NewYork NY USA 1995

[31] G J Anim-Kwapong K Opoku-Ameyaw F M Amoah et alCocoa Agronomy AReview Cocoa Research Insitute of GhanaNew Tafo-Akim Koforidua

[32] J A Winder ldquoCocoa flower Diptera their identity pollinatingactivity and breeding sitesrdquo PAN vol 24 pp 5ndash18 1978

[33] K H Hasenstein and M S Zavada ldquoAuxin modification ofthe incompatibility response in Theobroma cacaordquo PhysiologiaPlantarum vol 112 no 1 pp 113ndash118 2001

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

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BioinformaticsAdvances in

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Signal TransductionJournal of

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BioMed Research International

Evolutionary BiologyInternational Journal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

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Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

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Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology