Table 6. Yield of sweet potato grown on sand, Sanford, 1981.

Cultivar

147 days 188 days

Tons/acre rjry wt. Tons/acre Dry wt.

fresh dry- fresh dry

W119

W149

Travis

W125

Morado

W115

W154

10.6

7.0

5.5

6.7

3.0

7.5

8.1

2.5

1.5

0.9

1.5

0.8

1.5

1.5

23.8

21.9

15.7

23.0

25.1

19.9

17.9

21.2

18.3

14.4

14.1

12.9

12.1

—

4.7

3.8

2.1

3.2

3.3

2.1

22.0

21.0

14.9

22.5

25.6

17.5

Acknowledgements

This paper reports results from a project that contributes

to a cooperative program between the Institute of Food &

Agricultural Sciences (IFAS) of the University of Florida.

and the Gas Research Institute (GRI), entitled, "Methane

from Biomass and Waste."

Literature Cited

1. Bagby, M. O. 1981. Energy: Alternative sources for agriculture.

Proc. Great Plains Agr. Council, p. 3-10.

2. Hall, D. O., G. W. Barnard, and P. A. Moss. 1982. Biomass for energy in the developing countries. Pergamon Press, New York.

220 p.

3. LeGrand, F. 1980. Producing ethanol by a community distillery for

use as a fuel. Florida Agr. Expt. Sta. Cir. 482. 11 p.

4. Silva, J. G. da, G. E. Serra, J. R. Moreira, J. C. Concalves, and

J. Goldenberg. 1978. Energy balance for ethyl alcohol production

from crops. Science 201:903-906.

Proc. Fla. State Hort. Soc. 95:367-374. 1982.

WETLAND TARO: A NEGLECTED CROP FOR FOOD, FEED AND FUEL1

Stephen K. O'Hair

IFAS, University of Florida,

Agricultural Research and Education Center,

Homestead, FL 33031

George H. Snyder

IFAS, University of Florida,

Agricultural Research and Education Center,

Belle Glade, FL 33440

Julia F. Morton

Morton Collectanea, University of Miami,

Coral Gables, FL 33124

Additional key words. Colocasia esculenta.

Abstract. Taro (Colocasia esculenta Schott) is an aroid with large, heartshaped, peltate leaves arising from a starchy main, cylindrical, tapered corm from which may develop numerous rounded side cormels. The species is highly vari able and it is claimed that there are more than 1,000 types or races varying in habit, degree of acridity, tenderness, color of plant and corm, and adaptability to dry or wetland culture. Although it is grown commercially, most crop production and

harvesting is done manually. For the past 50 yr, tropical agriculturists have tended to

replace dryland taro plantings with cocoyam (Xanthosoma

spp.) which gives a higher yield with less labor. Neverthe less, wetland taro has a place under conditions unsuitable for dryland crops. Machines are being developed to replace sev

eral difficult and tedious manual operations.

The corms can be peeled and boiled, fried, or dried and made into flour. Taro chip production is currently com

mercialized. Both the tops and corms can be used to feed swine. All plant parts can be converted to carbon-based fuels.

Monthly harvests were made of March planted 'Lehua

iFlorida Agricultural Experiment Stations Journal Series No. 4386. This paper reports results from a project that contributes to a coopera

tive program between the Institute of Food and Agricultural Sciences ot the University of Florida and the Gas Research Institute, "Methane from Biomass and Waste". Mention of a chemical product does not imply endorsement or registration in the U.S. for that use on taro.

Proc. Fla. State Hort. Soc. 95: 1982.

Maoli' taro in a flooded Pahokee muck soil in Belle Glade, Florida. Noticeable corm development began in July. A maximum of 3404 kg dry weight/ha was recorded after 305 days of growth in January. Maximum corm and cormel pro duction was recorded in December with a total of 9,317 kg dry weight/ha. Top growth reach a plateau of 3300 kg dry weight/ha by September, which was maintained unfif a

January frost.

Taro, Colocasia esculenta Schott (syns. C. antiquorum var. esculenta Schott; Caladium esculentum Hort.), has, historically, been the most prominent of the edible aroids (family Araceae), and it has acquired various regional names: coco (Jamaica), tannia or eddoe (Trinidad), eddo (Barbados), taya (French West Indies), oto (Panama), tiquisque (Nicaragua), nampi or nampy (Costa Rica), quequeisque, quiquisque (El Salvador), makal (Yucatan), ashipa (Peru), inhame branco or inhame da costa (Brazil), gabi (Philippines), talo (Samoa), dalo (Fiji), kulkas (Egypt), kolocasi (Cyprus), kalo, keladi, or tales (Indonesia and Surinam). In Guatemala, Cuba and some other Spanish-speaking areas, it is sometimes called "malanga", a term better limited to Xanthosoma spp. (cocoyam) to avoid con

fusion (23).

Origin and Distribution

Believed native to India and neighboring regions of southeastern Asia, taro has been cultivated there and in the East Indies for more than 2,400 yr. Recent archaeological research in Papua New Guinea indicates that taro was

grown in the swamps of the Western Highlands Province as

much as 9,000 yr ago (42). Taro was introduced into Egypt about 2,000 yr ago, and

thereafter to Italy and Spain. From Spain it was carried to the New World. Meanwhile, it spread to various parts of tropical Africa and throughout the Pacific Islands and be came a staple food long before the sweetpotato was known in Oceania. The northern and southern limits of taro's range of cultivation are "upwards of 10 degrees beyond that of the greater yam" (Dioscorea alata L.) (6).

Over the past 300 yr, taro has taken second place to the

367

sweetpotato, and some taro-producing swamplands have

been abandoned in Papua New Guinea. Nevertheless, wet

land taro is still important in the Cook Islands, Fiji, the

New Hebrides, and in New Caledonia where irrigated plant

ing declined for some years and then was revived (42).

Today, 99% of Hawaiian taro production is in flooded

fields similar to rice paddies (Fig. 1). Even in this case all of

the actual crop production and harvesting is done by hand.

Fig. 1. The Hanalei National Wildlife Refuge on the Hawaiian

Island of Kauai, a major site of wetland taro production in the state.

Taro production by private producers is encouraged in this wildlife

refuge because it helps reverse the state's trend toward reduced areas

of wetlands, a trend that poses a threat to such wetland dependent

birds as the Hawaiian gallinule.

For the past 50 years, tropical agriculturists have tended

to replace dryland taro plantings with cocoyams (Xantho-

soma spp.) which give a higher yield with less labor.

Filipinos have come to prefer the mealy, mucilaginous

texture and the flavor of cocoyams. In tropical Africa, taro

and yams are giving place to cocoyams bacause the latter are

more suitable for manufacturing the staple pasty food

product, fufu. Yet, wetland taro obviously has a place under

conditions unsuitable for dryland crops. When grown under

flooded conditions, adapted cultivars grow more rapidly

and mature more quickly than when grown as dryland taro,

and yields may far exceed those of dryland taro (11, 42).

Description

Taro is a perennial herb with erect, peltate, heart-shaped,

downward-pointing leaves 12 to 60 cm long, 7 to 50 cm

368

wide, on green, green-and-purple, or wholly purple, suc culent petioles 40 to 150 cm long. Leaf color varies from

light- or dark-green to more or less purple. The incon

spicuous inflorescence which forms seasonally (1 or from 2 to 5 together) is a cylindrical spadix about 10 cm long,

yellow or reddish above and green below. Male flowers

occupy 2.5 to 5 cm of the upper part and are separated by a

space from the female flowers which cover 2.5 to 5 cm of

the lower part. The whole inflorescence is shielded by a yellow-and-green spathe about 24 cm long. Seeds are seldom

set without hand-pollination although natural seed set oc

curs in some cultivars (40, 44). Some forms never have stout

corms or rhizomes (underground stems), but edible taro

has a starchy main, cylindrical, tapered corm, ranging up to

50 cm long and 20 cm wide, from which may develop sev

eral rounded lateral cormels. All are surrounded by a mass

of thick, cordlike feeder roots. Externally, corms and cormels

are brown-skinned, encircled by fibrous rings. Internally,

the corms or cormels may be white, yellow, orange, red, brownish-red, or purple. Cut surfaces often discolor when

exposed to air. There is great variation in the degree of acridity.

Varieties

The species is highly variable and it is claimed that there

are more than 1,000 types or races varying in habit, degree of

acridity, tenderness, color of plant and corm, adaptability to

dry or wetland culture, and suitability tor various food uses.

Var. aquatilis Hassk., with long, slender stolons and with

out a swollen corm, has levels of cold tolerance and is

naturalized along bodies of fresh water in the southern United States (1).

In 1903, O. F. Cook (9) reported that Californians of

Chinese history had "recently" started raising Chinese taro,

corms of which were being imported from Canton and Hong

Kong. The French name, "Taro de Chine" in Indochina,

was anglicized as "dasheen". This form which produces

abundant small cormels, became popular in the West Indies.

Dasheen is the botanical variety C. esculenta var. globulifera

R. A. Young and includes the cultivars 'Globulifera' (per

haps the same as 'Trinidad*), 'Sacramento', and 'Ventura'.

In Hawaii dasheen is called "Japanese" taro. Plants produc

ing only a central corm are classed as "Chinese" taro (8).

A taro collection started by O. W. Barrett in Puerto Rico

was transferred to Brooksville, Florida, in 1906, and the

United States Department of Agriculture made vigorous

efforts to promote dasheen growing throughout the southern

states (20). Nonetheless, taro has never competed success

fully with the potato and sweetpotato in this country (18).

In 1939, Whitney et ah (49) described 56 dryland and 31

wetland cultivars in Hawaii. A collection of 154 cultivars

(56 Hawaiian, 62 from other Polynesian sources, 28 Mela-

nesian, and 8 from other countries) is maintained under

dryland culture by the Harold L. Lyon Arboretum in the

upper Manoa Valley near the University of Hawaii campus

(2) (Fig. 2).

Only 5 or 6 cultivars are grown commercially in Hawaii. 'Lehua', the main cultivar, produces a pinkish-fleshed corm.

Others are 'Piko uaua', 'Piko kea', and 'Uliuli' (mostly

white-fleshed); and 'Maui Lehua' and 'Piialii' (reddish-

fleshed). The red-fleshed cultivars are preferred for poi (35).

The cultivar 'Sar kachu' is grown in Bengal as an aquatic, producing corms 15 to 30 cm long (48).

Cultivation

In India, Oceania and parts of Africa, wetland taro is often a fringe crop grown along rice paddy borders, ponds and streams. Larger plantings may require field leveling and

Proc. Fla. State Hort. Soc. 95: 1982.

Fig. 2. Mr. Don Anderson, Curator of the Harold L. Lyon Arboretum

taro variety collection pictured with a portion of the 150-plus selections

he has maintained for many years. Mr. Anderson has been growing taro

for over 60 yr.

puddling by plowing, disking, harrowing and grading along

with the development of drainage ditches 12.5 to 15 cm

deep around the inner field edges. Dike building is generally

necessary to control water depth and flow. Constant water

circulation is necessary to avoid root rot, to which most

cultivars are susceptible in warm, stagnant water.

Water depth should be maintained at 2.5 to 5 cm from

planting until the plant is well anchored in the soil. There

after water level is raised to fully cover the lower half of the

plant. Additional culture includes a drainage period of a

few days before and after the application of fertilizer (36),

and before harvesting to weaken the root structure and

facilitate removal of corms. Plantings can be made year

round (35). Mechanized planting is being explored in

Hawaii and a tractor for planting dryland taro has been

developed in Fiji (39); nevertheless wetland culture is still

largely manual.

Setts (corm and cormel crown cuttings with 15 to 25 cm

of leaf petioles attached), called "hulis" in Hawaii, are

pushed into the soil by hand. The base is submerged 5 to

7.5 cm or until moist soil has been reached. The corm gives

a higher yield than the smaller cormel. Spacing may be

much closer than with dryland taro, ranging from 12,000 to

100,000 plants/ha (11). However, the wider the spacing, the

larger the corm size. Planting at average densities may re

quire 15 to 20 man hr/ha (35). It has been found that taro

plants grown on mounds in flooded land are more produc

tive than plants grown on the level.

Adequate N is essential to taro. It is usually incorporated

into the soil at the outset because the plant requires most

of its N during the early stages of growth, and also to min

imize N losses through leaching and flooding. Wetland taro

has given good yields with application of 250 kg N and 250

kg K/ha. Fertilizer trials with wetland taro in Hawaii

showed highest yields in plots given 1120 kg/ha N. Yields

in a soil with high P fixation capacity were increased by

1120 kg/ha P and delaying harvesting to 15 months. Appli

cation of K gave no significant increase in corm yield (12,

13). Well fertilized paddies may yield 35,000 to 50,000 kg/ha,

twice the yield of sweetpotato (19).

In wetland culture, weeds are largely controlled by water

depth. Nevertheless some hand- or chemical-weeding is

needed. Propanil, prometon, prometryne and nitrofen are

considered appropriate for weed control in wetland culture

if necessary (3). However, no herbicide has yet been reg-

Proc. Fla. State Hort. Soc. 95: 1982.

istered for use on taro in Florida by the U.S. Environmental Protection Agency (EPA).

The wetland crop should be ready for harvesting in 12

to 15 months from planting. Corms cannot be left in the

ground as long as those in upland culture. The plants are

considered to be mature when the newest fully expanded

leaves are smaller than the older leaves. Corms taken from

immature plants are edible, however they do not store as

well as those from mature plants. At harvest the fields are

generally re-flooded.

It is usually necessary to cut through the feeder roots in

a circle around the plant to facilitate harvesting. Laborers

usually are equipped with a 1.5 to 2 m pipe with a sharp

ened tip (35). The remaining roots are manually detached

and the corms washed in the field, then put in mesh-

bottomed buckets and rafted to dry land (Fig. 3), where

they are further cleaned, bagged and then trucked to dealers

and processors (35).

Fig. 3. Windrowed taro corms and cormels with attached 'hulis'

ready for separation and loading onto a raft which is winched by the

tractor in the background to the dike roadway for transport from the

field.

Hawaiian growers look forward to the day of mechanical

harvesting. A horizontal auger tractor attachment has been

devised which can dig and windrow flooded taro (24, 35).

Compared to hand-digging, it takes 1/10 of the time. How

ever, it lifts up the corms with a thick coating of mud which

handicaps the manual cleaning and collecting operations. Therefore, pickup and cleaning machines are under develop ment (21,41).

Diseases and Pests

Leaf blight caused by Phytophthora colocasiae Rac. is a

common problem in taro paddies in Oceania and the Orient.

Attempts at chemical control have been partially successful (16, 17). Some cultivars may be tolerant to this disease. Leaf spot caused by Cladosporium colocasiae Samada is most

evident on older leaves. Copper fungicides will control it. Soft rot or pythium rot of the corm resulting from infection by several soil-borne species of Pythium has caused severe losses (10-50 or even 100%) in Hawaii. Sanitary measures, soil treatment with Captan 50W at 100 kg/ha and crop

rotation are effective means of control in acid soils. In the British Solomon Islands, Fusarium oxysporum Schlecht emend. Snyd. et Hans, has been found responsible for corm

rot in actively growing taro (17). Dasheen mosaic virus is the most common virus disease. Yield loss in taro as a result of this disease has not been documented.

Taro leaves are attacked by the taro leaf hopper (Taro-

369

phagus proserpina Kirkaldy. An effective predator, the Philippine sucking bug (Cyrtorhinus fulvus Knight) has

provided adequate control of this pest in the Eastern Caro

line Islands. Taro plants may be defoliated by the sweet-

potato hawk moth caterpillar (Hippotion celerio L.) or by

the small grasshopper, Gesonia sanguinolenta, and the cater

pillar, Agrius convolvuli L. Injuries also result from attacks

of other insects: striped mealybug (Ferrisia virgata

Cockerell), thrip (Heliothrips indicus Bagn.), taro thrips

(Organothrips bianchii Hood and Pseudobryocoris colo-

casicus Carvalho) and aphid (Aphis gossypii Glov.). Taro

beetles (Papuana laevipennis Arrow and P. huebneri Fairm)

feed on the stems and roots but may be deterred by soil ap

plications of dieldrin or aldrin (3, 23). The nematode

Meloidogyne incognita (Kofoid k White) Chitwood, has

been found on feeder roots of wetland taro in Trinidad (4).

Storage

Corms and cormels can be kept in storage at 10°C with

adequate ventilation for over 5 months (36). Shelf life at

ambient (ca. 25 °C) temperatures can be several months (22).

Food Uses

All parts of the taro plant contain irritant crystals of

calcium oxalate and/or an acid sapotoxin with definite seasonal variation, the concentration being highest at the

end of the dry season (32, 38, 46). Other factors besides

calcium oxalate have been associated with the acridity (31). 'None o£ the plant parts can be eaten raw. Most of the ir

ritant is in or near the skin and therefore is largely removed

by peeling (45). To reduce irritation of the hands, peeling

can be done underwater (6) or plastic gloves can be worn.

In Hawaii, taro is often pre-peeled for sale, being kept in

water to avoid discoloration (8). Thorough cooking elimi

nates the irritant in most cultivars.

In Oceania, whole taro is commonly roasted on stones or baked in ovens. The corm may be peeled, sliced or diced

and steamed, boiled or baked. In New Caledonia, peeled, sliced corms with chicken or fish and coconut cream are

wrapped in leaves and roasted (28). Corms are less

mucilaginous than the cormels, mealier and richer in flavor (48), and are better for making chips. Taro chips are made

like potato chips but absorb less fat and have a distinctive flavor (Fig. 4) (20, 33). Boiled corms are sometimes formed

into patties or fritters and fried, and are often added to

stews. In the Philippines, the boiled, sliced corms are sprin

kled with sugar and coconut (5). Japanese in Hawaii boil

peeled, cut-up corms for 7 min, drain, add sugar and soy

sauce and boil again till tender. They also fry and then

simmer diced corms with sliced meat, onion and a little soy sauce, or slice the corm and then cook it with chopped

pork and ham or bacon and diced shrimp. The mixture is

folded into batter, and steamed (8).

In Hawaii and Polynesia poi is a slightly fermented

paste of boiled and mashed taro which is easily digested and

considered beneficial to invalids and infants (Fig. 4). As a

part of the main meal, the paste may be eaten as such or

made into patties and baked or toasted. Poi is even added to

chocolate ice cream mix. There are several commercial

processors in Hawaii. The Julliard Fancy Foods Company

of San Francisco sells "Ready-mixed poi" through grocery

stores at $1.19/0.45 kg net weight jar. In southeast Asia, taro

is often preserved by salting and drying for future use (19).

Solar drying is a potential alternative where salt is not available (30).

Flour can be made from fresh or pre-cooked corms. Much

like potato flour, it is used in soups, gruels, puddings, gravies

370

Fig. 4. Ready mixed poi (jar in center) and several brands of taro

chips are widely available in Hawaiian markets.

and is used either alone or mixed with other flours to make

pancakes, rolls, cookies and bread (28, 48). The dough can

be kept for a long time in sealed metal boxes (28).

Young leaves and petioles of "luau" types, low in acrid

ity, are commonly eaten as greens (27, 34) after boiling

twice or adding baking soda, lime or lemon juice, milk,

butter or other fat when cooking to reduce or eliminate the

acrid properties. As a safeguard, it is best to peel the petioles

since the cuticle contains most of the irritant (10). Thorough

cooking may take 30 to 45 min (29). The leaves are an im

portant ingredient in calalu soup in Trinidad (19). They

are prepared as a creamed soup in Hawaii (27). In Samoa,

after removing the midribs, taro leaves are stacked on a

breadfruit-leaf "platter", filled with coconut cream, rolled

up and cooked on hot stones. In Tahiti, leaves and peeled

petioles are layered with chicken or pork, topped with

coconut cream and lemon juice, rolled up and cooked in an

oven (28).

Very young blanched shoots are obtained by mounding

up mature corms with soil or sphagnum moss in a dark

place, or in raised greenhouse beds with bottom heat and

heavy shading (50). Long, slim, white or white-and-purple

shoots will emerge. When 20 to 30 cm long, they are cut off,

bundled and sold in the market. They are cooked till tender

in salted water. Japanese farmers in Hawaii produce these

shoots on a commerical basis as "asparagus taro top" (Fig.

5) (8).

Food Value

Where a population is dependent on wetlands for a

starchy food staple, taro may be a better choice than rice

from the standpoint of human nutrition (14). In fact, it

equals potato for amino acid content (Table 1). Dr. David

Fairchild, in commenting on Hawaiian dietary studies,

wrote that "Japanese babies and children brought up on a rice diet in this tropical climate develop serious dental dif

ficulties. When fed on a diet of poi [made from taro], they

have strong teeth and far better health" (15). He was re

ferring to the results of an investigation by Dr. Nils P. Lar

son of Honolulu who conducted his nutritional experiiueut

with the people on a plantation of the Hawaiian Sugar Planters* Association (18).

Corms contain about 64% moisture, 32% carbohydrate

and 2% protein (Table 2). Leaves of certain cultivars are a

good source of calcium, phosphorus, carotene and vitamin

C, if the cooking water is not discarded (27). The starch

grains contain 28% amylase (46), are among the smallest of

Proc. Fla. State Hort. Soc. 95: 1982.

Table 2. Average nutritional value of taro (nutrients in 100 g edible

portion).

Fig. 5. Taro shoots (petioles) grown in the dark for use as "asparagus

taro top".

Table 1. Amino acid content of taro corms in comparison with potato

(mg in 100 g edible portion).

Conns Leaves

Young

shoots Petioles

Calories 137.0z 34.0y 33.0* 29.0*

Moisture (%) 64.4 89.9 89.5 93.0

Protein (g) 2.2 2.5 3.1 0.9

Fat (g) ' 0.2 1.0 0.6 0.2 Carbohydrates (g) 32.0 5.3 5.7 3.8

Fiber (g) 1.0 2.1 3.2 1.0

Ash (g) 1.2 1.3 1.1 1.3

Calcium (mg) 16.0 95.0 49.0 25.0

Phosphorus (mg) 47.0 328.0 80.0 12.0

Iron (mg) 0.9 2.0 0.3 0.5

B-Carotene eq. (mg) tr. 3300.0 — 180.0

Ascorbic acid (mg) 8.0 37.0 82.0 13.0

Thiamine (mg) 0.1 0.1 — tr.

Riboflavin (mg) 0.1 0.3 - tr.

Niacin (mg) 1.2 1.5 — 0.4

zfrom references 25, 26, 47.

yfroin references 25, 26

sfrom references 8, 25, 26

wfrom references 7, 8, 25, 26

suggest that it may be a crop that could be readily adapted

to Florida wetlands with final use as food, feed or fuel. To

observe taro growth and development on a flooded muck

soil an experimental planting was made at Belle Glade

(Fig. 6).

Taro Potato

Isoleucine

Leucine

Lysine

Methionine

Cystine

Phenylalanine

Tyrosine

Threonine

Tryptophan

Valine

Arginine

Histidine

Alanine

Aspartic acid

Glutamic acid

Glycine

Proline

Serine

160

128

58

21

153

64

129

24

141

119

42 49

217

95

81

74

137

77

125

106

22

19

67

54

77

21

115

105

35

80

262

352

70

77

70

zfrom reference 37

any plant and are more easily digested than those in other

foods (48).

Other Uses

Taro can be employed as feed for domestic stock (43).

In addition there is much interest in the potential of taro as

raw material for the production of bio-fuels. For this pur

pose taro has value in that it is well adapted to lowland

soils that are not of value for most other crops. It currently

is not of great economic importance in the United States for

food or export and its concentrated carbohydrates can be

readily converted to carbon based fuels.

Experimental Florida Planting

The versatility of taro along with its potential yields

Proc. Fla. State Hort. Soc. 95: 1982.

Fig. 6. An experimental planting of 'Lehua Maoli' taro grown in

flooded Pahokee muck soil at the University of Florida, IFAS, Agricul

tural Research and Education Center in Belle Glade as part of a taro

production study conducted in 1981.

Setts of 'Lehua Maoli' taro received from Dr. Ramon

de a Pena, University of Hawaii, were planted in 0.5 m

spacings in unflooded Pahokee muck soil at the AREC-Belle

Glade on March 5, 1981. The plot area had been cropped

to rice in 1979. Triple superphosphate was applied prior to

the taro planting to provide 30 kg P/ha. The field was

flooded so that the bottom half of the plants was covered, once the plants were established.

At 1-month intervals, 6 randomly selected whole plants

were harvested and divided into their constituent parts

(leaves, petioles, corms, cormels, roots and unidentifiable

senescent material). Fresh and dry weight yields were de

termined for each part, and the harvested material was

analyzed for starch and glucose. The monthly harvests were

made through March, 1982, and a final harvest was taken in

June, 1982. A severe freeze (—6°C) occurred on January 12,

1982. Taro leaves and petioles above the water line were

371

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Proc. Fla. State Hort. Soc. 95:374-376. 1982.

ABSORPTION AND TRANSLOCATION OF SOME

GROWTH REGULATORS BY TOMATO PLANTS GROWING

UNDER UV-B RADIATION AND THEIR EFFECTS ON FRUIT QUALITY AND YIELD

Agustin Prudot and Fouad M. Basiouny1

Department of Agricultural Sciences,

Tuskegee Institute,

Tuskegee Institute, Alabama 36088

Additional index words. Carotenoids, ascorbic acid, total

soluble solids.

Abstract. An experiment was conducted in the green

house to study the effects of UV-B irradiation on the absorp

tion and translocation of indoleacetic acid, gibberellic acid,

2,3,5-triiodobenzoic acid, 6-benzylamino purine, kinetin,

and ethylene by tomato plants. UV-B induced variable effects

on the absorption and translocation of different growth regu

lators. Regardless, of the growth regulator treatments plant

height, yield, total soluble solids, pH, carotenoids and

ascorbic acid were slightly reduced under UV-B enriched

conditions which indicated a direct effect of UV-B on different

morphological and physiological processes of the tomato

plants.

Plants growing in their natural habitat are constantly

exposed to radiant energy of all wavelengths from the sun

which reaches the surface of the earth. An important por

tion of this electromagnetic radiation is the ultraviolet.

There has been a growing concern that effluents from super

sonic and other highflying crafts, chlorofluoromethane, re

frigerants and aerosol propellants, that diffuse to the

iGraduate Student and Professor of Plant and Soil Sciences, respec

tively.

374

stratosphere could cause a reduction of atmospheric ozone

(1, 4, 9). This would result in a concomitant increase in

penetration of solar ultraviolet radiation to the earth's sur

face with possible biological consequences (5). Simulating

various atmospheric ozone concentrations, many investi

gators showed reduction in many aspects of plant growth

and development due to the exposure of plants to the UV-B

irradiation. The use of growth regulators to accelerate, re

tard, or modify plant growth and development is now com

monly accepted. Absorption and translocation of these com

pounds depend on many internal as well as environmental

conditions. Light quality has been reported to affect the

uptake of many organic and inorganic substances (8). This

experiment was conducted to evaluate the absorption and

translocation of several growth regulators by tomato plants

growing under UV-B conditions and their effect on fruit

quality and yield.

Materials and Methods

Tomato (Lycopersicon esculentum Mill cv. 'Walter')

seeds were planted in the greenhouse in a mixture of ver-

miculite, peat moss, and fine sand (1:1:1 by volume). Seeds

were germinated under ultraviolet light UV-B ( + UV-B) or

without UV-B (-UV-B) (UV-B = 280-310 nm,) in a ran

domized block design. When the plants reahed the second-

leaved stage, they were sprayed with six different growth

regulators (Table 1). UV-B irradiance was supplied by

twelve Westinghouse FS40 Sun Lamps filtered through

either cellulose acetate for (+ UV-B) or mylar film for

(-UV-B). The plants received a total of 872 hr of UV-B

irradiation during the growing season. The temperature of

Proc. Fla. State Hort. Soc. 95: 1982.