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CANADIAN TREE IMPROVEM ENT ASSOCIATION/
ASSOCIATION CANADIENNE POUR L’AMÉLIORATION DES ARBR ES
Tree Seed Working Group
NEWS BULLETIN No. 37 June 2003
THIS ISSUE AT A GLANCE
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Article
CHAIR’S ‘ARMCHAIR’ REPORT
EDITOR’S NOTES
EFFECTS OF PHOTOPERIOD ANDMOIST CHILLING ONGERMINATION OF WHITE ANDYELLOW BIRCH SEEDS
MAXIMIZING QUALITY OF Betulapapyrifera SEED
BOOK REVIEW
HARDWOOD SEED TREATMENTSIN QUÉBEC
HARDWOOD SEED STORABILITYREVISITED
SEED TESTING MANUALS
UPCOMING MEETINGS
SELECTED REFERENCES –HARDWOOD SEED
RECENT PUBLICATIONS
CHAIR’S ‘ARMCHAIR’ REPORT
W elcome back. I hope you enjoy our newelectronic format and that it reached youpainlessly. This News Bulletin will focus onhardwood seed and I’d like to thank everyone whocontributed. Our next News Bulletin will focus on“Seed Orchard Practices” and we are lookingforward to contributions from researchers andoperational facilities on the practices they employfor effectively and eff iciently producing seed fromselected parents.
Hardwoods are a minor, but important part ofCanadian forestry. Hardwood seed is not as wellstudied partly because most aggress ive programsuse vegetatively propagated materials. Mosthardwood species also have a more complicatedseed biology system than conifers. A betterappreciation of the positive attributes of coniferseed is often the result of starting to work withhardwoods. They present much greater variabilitybetween genera and it is not uncommon thatspecies within a genus have very different seedbiology “strategies”. An exciting area ofinvestigation for some and a frustration for thoseneeding to operationally germinate hardwoodspecies for which very little information isavailable.
In hardwood species, seed immaturity can be amore significant issue with some species sheddingseeds with immature embryos. Many hardwoodscan also be considered recalcitrant (see NewsBulletin #33 for a review) or cannot be dried andstored at low moisture contents, therefore quick lylosing their viability. This complicates anyreforestation system that is dependent on thisseed. Hardwoods also comm only have complexdormancy mechanisms that may require muchmore than the com monly used ‘month’ of moistchilling to overcome dormancy and initiategermination. Some species require very longstratification periods (one year or more), chemicaltreatments, moisture content control, scarification,and a host of other specialized treatments.Hardwood species are generally more d ifficult toprocess and I suspect that a large amount of thevariab ility we see between seed lots is due toquality of seed processing and collection timing.These have improved greatly with our conifersover the past few decades, but we have a long
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way to go with our hardwoods. There is still a greatdeal of work to do in this area – Good Luck.
Planning is currently underway for the 29 th
Canadian Tree Improvement Association meetingin Kelowna, BC from July 26 – 29, 2004. Thetheme of the meeting is “Climate Change andForest Genetics”. A Tree Seed W orking Groupworkshop will be held on Monday, July 26 and Iwelcome all suggestions on potential topics. Myinitial thoughts have focused on two possibilities:a) Quality Assurance monitoring and b) Crownarchitecture and its control. Feedback on these orother topics is greatly encouraged. For those ofyou travelling through Vancouver I am also goingto arrange a pre- or post-conference tour of ourBCMOF Tree Seed Centre for those interested.Please indicate if you are interested.
There are a variety of seed-related meetingsoccurring this summ er and fall (check UpcomingMeetings section). I encourage everyone with thetime and funds to try and attend at least one ofthese meetings. W e would also greatly apprec iatebrief reports or opinions of meetings that mem bersattend. Have a great summer!
Dave KoloteloTSW G Chairperson
EDITOR’S NOTES
Hello again Folks and welcome to the firstelectronic version of the News Bulletin! I hope youwere able to read and/or print it with no problems.
You will find several articles dealing with hardwoodseed which I hope you will find interesting. The“Selected References” section is a good place tostart if anyone is looking fro some informationabout a particular species. And, of course, there isthe USDA W oody Plant Seed Manual web sitehttp://wpsm.net .
More good news!! The TREESEED DiscussionGroup is online again. This forum has the potentialto be a very useful means for comm unicationamong subscribers. If anyone has any questions,comm ents, announcements, etc. dealing with treeand shrub seed, then the Discussion Group is anexcellent means of obtaining and/or disseminatinginformation. If you are unsure whether or not yousubscribed in the past, please subscribe again.That way the mem bership list will contain yourcurrent, active e-mail address.
T o s u b s c r i b e - S e n d e - m a i l t o :[email protected] with the message consistingof the following single line SUBSCRIBETREESEED firstname lastname . A messageconfirming that your name has been added to thelist will be sent to you.
To send a message to the list - Send an e-mail to:[email protected] .
I look forward to some good discussions.
Dale SimpsonEditor
TREE SEED WORKING GROUP
ChairpersonDave Kolotelo
BC Ministry of ForestsTree Seed Centre
18793 - 32nd AvenueSurrey, BC V4P 1M5
Tel.: (604)541-1683 x 228Fax.: (604)541-1685
E-mail: Dave.Kolotelo@gem s7.gov.bc.ca
Editor of the News BulletinDale Simpson
Natural Resources CanadaCanadian Forest ServiceAtlantic Forestry Centre
P.O. Box 4000Fredericton, NB E3B 5P7
Tel.: (506) 452-3530Fax.: (506) 452-3525
E-mail: [email protected]
Comments, suggestions, and contributions for theNews Bulletin are welcomed by the Chairperson orEditor.
EFFECTS OF PHOTOPERIOD AND MOISTCHILLING ON GERMINATION OF WHITE AND
YELLOW BIRCH SEEDS
This trial was one of the tasks taken on by theTree and Shrub Seed Sub-comm ittee of theAssociation of Official Seed Analysts (AOSA) toreconcile some of the differences in germinationtesting rules for some tree and shrub seedsbetween the International Seed T es tingAssociation (ISTA) and AOSA. This trial wascarried out in 1983. The over-all results had beenreported to the Sub-comm ittee at the AOSAannual meeting in 1983. I thought that the trialresults for white birch (Betula papyrifera Marsh.)and yellow birch (B. alleghaniensis Britt.) may beof interest to seed users.
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Methods and M aterials
The seed lots used for this trial were taken fromthe Seed Bank of the National Tree Seed Centreat the former Petawawa National Forestry Institute,Chalk River, Ontario. Four seed lots from differentcrop years, locations, and seed quality wereselected from each species for this purpose. Thetrial was designed to examine how pre-treatment(no chilling and 21-day moist chilling ) andphotoperiod (0, 8, and 16 hours) affect seedgermination of the two birch species. Birch seedlots, especially white birch, have a high percentageof empty seeds due to the difficulty in removingempty seeds. To evaluate the real treatment effect,all seeds were x-rayed with a Hewlett PackardFaxitron x-ray unit on Kodak M® film at 15 kvp,3ma using 60 and 80 second exposure times forwhite and yellow birch seeds, respectively. X-radiography was used to identify and quantityempty seeds and to adjust the germinationpercentages based on filled seeds.
Germination was carried out on moist blotter paperwith a layer of Kimpak® underneath in thePetawawa germination box (Wang and Ackerman1983) in a Conviron G30 germinator (ControlledEnvironments, W innipeg) at diurnal temperaturesof 30°C with an 8 or 16 hour photoperiod and of20°C for 16 or 8 hours darkness. For eachtreatm ent, random samples of four replications of100 seeds each were used. Moist chilling wasdone by placing the dry seeds on top of the moistblotter paper germination medium and storingthem in a cold room at 2–4°C. Both the control andtreated seeds were scheduled to germinate at thesame time. Germination was monitored weeklyand the criterion for evaluation was based on filledseeds and vigor classes 1–4 (W ang 1973).
Statistical analysis was conducted to evaluate theeffects of moist chilling and photoperiod on thegermination data using the GLM procedure ofSAS® (SAS 2001).
Results and Discussion
Seed Quality
Seed quality, in terms of percentage of filledseeds, varied with seed crop years and seedsources (Table 1). The percentage of empty seedsranged from 4–55% for yellow birch and from16–89% for white birch seed lots. The highpercentage of empty seeds (16–89%) in the whitebirch seed lots is higher than the 14–47% emptyseeds in a white birch seed crop reported bySafford et al. (1990). Such variation in thepercentage of filled seeds among seed lots seemsto reflect the importance of collecting seed inbetter seed years when the percentage of emptyand discolored seeds is lowest (Safford et al.1990). This could also be simply due to differentprocessing efficiencies. The high percentages ofempty seeds in white birch can be reduced by onlycollecting seed in good seed years which occurevery other year. Because of the general problemin seed processing and purity analysis of birchseeds, ISTA (2003) prescribes germination testingby weight replicates (four rep lications of aspecified weight of seeds; for the two Europeanbirches, Betula pendula and Betula pubescens, thereplicate weight is 0.1g). However, theprescription for germination testing of white birchseeds remains the same as other conifers in theISTA rules. To obtain uniform results in laboratorytesting and nursery sowing, birch seeds should befurther processed by liquid flotation methods whichcan effectively remove empty, insect damaged,and defective birch seeds (Bjorkroth 1973).
Table 1. Percentage of filled seeds based on x-radiographic images by species and seed lots
Filled seeds (%)
Species Seed lot1 Provenance Rep. range Average Empty seeds (%)
Yellow birch 672044 Harr ington, Qc 31–56 45 55
673053 Alginquin Park, ON 62–82 76 24
703092 Chalk River, ON 92–99 96 4
743493 Algonquin Park, ON 76–94 86 14
W hite birch 752041 Verendrye Park, Qc 23–31 27 73
754032 Agassiz Forest, MB 23–31 27 73
773200 Ramsey Lake, ON 76–90 84 16
777193 Hope, BC 7–20 11 891 the first two numbers represent the collection year
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Seed Dormancy
Yellow birch seeds have a water-soluble inhibitorin the seedcoats that can be alleviated by light ormoist chilling (Erdmann 1990). The degree of seeddormancy, in terms of increased germination by21-day moist chilling under 8-hour photoperiod,varied between seed lots ranging from 4–23% in
yellow birch (Figure 1 and Table 2). Although whitebirch seeds are not considered dormant, someseed lots seemed to respond positively to bothextended photoperiod and moist chilling (Table 2).According to Bevington and Hoyle (1981), whitebirch is induced to germinate by moist chilling at3°C or by red light which is mediated byphytochrome.
Table 2. Effects of moist chilling and photoperiod on germination of yellow and white birch seed from four provenances
Percent germination by chilling and photoperiod
Non-chilled 21-day chilled
Photoperiod Photoperiod
Species Seed lot 0 8 hrs 16 hrs 0 8 hrs 16 hrs
Yellow birch 6630530 6 73 79 53 81 84
Yellow birch 6720440 27 74 78 59 78 76
Yellow birch 7030920 5 57 73 36 80 73
Yellow birch 7434930 30 76 73 70 80 77
Average 17 70 76 54 80 78
W hite birch 7520410 40 80 81 72 67 88
W hite birch 7540320 25 62 68 53 72 79
W hite birch 7732000 77 87 96 93 98 95
W hite birch 7771930 31 76 67 61 41 64
Average 43 75 78 70 70 82
Effect of Photoperiod
The presence of light significantly improvedgermination of yellow birch seeds (Table 3).Germination of non-chilled seeds increased anaverage of 53% at the 8-hour and 59% at the 16-hour photoperiod compared to those germinated inthe dark. For chilled seeds, germination increased26% at the 8-hour and 24% at the 16-hour
photoperiod compared to the dark (Table 2).Although the extended photoperiod did notsignificantly improve germination over that of 8hours, it improved germination of three of the non-chilled seed lots (4–16%) but only one chilled seedlot (3%) (Table2). According to Erdmann (1990),germination tests are conducted at alternating dayand night temperatures of 30°C and 20°C with atleast 8 hours of light for non-chilled seeds.
Table 3. Effect of photoperiod and moist chilling on mean germination of yellow and white birch seed
Photoperiod Chilling
Species 0 hrs 8 hrs 16 hrs non-chilled chilled
Yellow birch 36 75 77 54 71
W hite birch 57 73 80 66 74
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Although analysis of variance showed nosignificant effect of photoperiod on germination ofwhite birch seed, germination did increase withincreasing photoperiod (Table 3). In general, whitebirch seeds seemed to be able to germinate betterin darkness than yellow birch, although light wasessential for maximum germ ination. W hile 8 hoursof light improved germination of non-chilled seedsby 10–45%, the extended 16-hour photoperiodfurther improved the germ ination by 1–9% forthree out of the four lots tested (Table 2).Germination of chilled seed was variable with inseed lots between the three photoperiods (Table2). Apparently, the response of non-chilled seedsto light treatment and germination temperaturevaries with seed source of white birch (Bevingtonand Hoyle 1981).
Effect of Moist Chilling
Standard laboratory germination tests for yellowbirch seeds prescribed by AOSA (2002) requirepaired tests (i.e., with and without 21-day moistchilling). Moist chilling improved germination 17%(Table 3). These results are quite different fromEardmann (1990) who reported that germ inationtest results of ye llow birch are always higher fornon-chilled than chilled seeds. W hen yellow birchseeds were moist chilled, extended photoperiodhad a small positive effect on the total germinationof one seed lot (Table 2). Moist chilling alsoimproved seed germination in darkness, however,the differences in germination between chilled andnon-chilled sed decreased as photoperiodincreased (Figure 1). The 21-day period of moistchilling proved to be adequate for com pletegermination of yellow birch seeds due to a smallerpercentage being classified as low vigor.
Figure 1. Effects of moist chilling and photoperiod on the germination of four yellow birch seed lots (each bar represents the m ean of 16 replicates of 100 seeds each).
Although white birch seeds were not considereddorm ant, moist chilling was found to be beneficialto the germination of two lots (10–11% increase),but detrim ental to two others for the 8-hourphotoperiod (Table 2). Seed that was moist chilledhad higher germination in the dark than non-chilledseed (Figure 2). Past experience has indicatedthat moist chilling does not have a detrimentaleffect on germ ination of non-dormant seeds unlessthe seeds were damaged in processing or thetreatment is improperly applied. However, it is
interesting to note that some white birch seed lotsfrom New Ham pshire, Alaska, and Ontario showeda loss of moist chilling stimulus following variousperiods of m oist chilling when germinated at alower tem perature of 18°C (Bevington and Hoyle1981). This is quite unusual because coniferousseeds become less sensitive to germ inationtemperature following moist chilling (W ang, 1987).Moist chilling was especially effective byincreasing the germination of white birch seed inthe dark (Figure 2) (Bevington and Hoyle 1981).
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Figure 2. Effects of moist chilling and photoperiod on the germination of four white birch seed lots (each bar represents the m ean of 16 replicates of 100 seeds each).
The following conclusions can be deduced fromthe above results: 1. In view of the variability in seed quality, in
terms of filled seeds and previousresearch findings, birch seed collectionsshould be made in the best seed cropyears. To im prove seeding effic iency ofbirch seeds, seed lots with lowpercentages of filled seeds should beupgraded by liquid flotation techniques toremove empty and insect damagedseeds. This is especially critical forcontainer seedling production.
2. Yellow birch seeds are dormant andrequire 21-day moist chilling for maximumand uniform germination. This confirmsthe current AOSA prescription for thisspecies (AOSA, 2002). Since moistchilled seeds can not only germinatebetter and faster but can also germinate atlower temperatures and low light intensity,it would be technically and economicallyadvantageous to incorporate theupgrading and moist chilling pre-treatmentinto container seedling production.
3. For white birch seeds, 8 hours of light areessential for maximum seed germinationalthough extended photoperiod and moistchilling treatment could further enhancegerm ination. The prescriptions forlaboratory germination testing of whitebirch seeds between AOSA and ISTA arethe same except the recommendation for
using a 16-hour photoperiod by AOSA(2002).
Acknowledgements
I would like to thank Steve D'Eon and DaveKolotelo for reviewing the manuscript, MargaretPenner and Craig Robinson for assistance instatistical analysis, and Gordon Brand and BlairKelley for making graphs and tables.
References
AOSA. 2002. Rules for testing seeds. Assoc. Off.Seed Anal., Las Cruces, NM, USA.
Bevington, J.M.; Hoyle, M.C. 1981. Phytochromeaction dur ing prechil ling inducedgermination of Betula papyrifera Marsh.Plant Physiol. 67: 705-710.
Bjorkroth, G. 1973. Separation of birch seeds inliquids according to density. in Proc.IUFRO Int. Symp. on Seed Processing,Bergen, Norway, 1973, Vol.1, Paper # 3.
Erdmann, G.G . 1990. Betula alleghaniensisBritton. Yellow birch. Pages 133-147 inR.M. Burns and B.H. Honkala, Tech.Coords. Silvics of North America, Vol. 2,Hardwoods. USDA, For. Serv., Agric.Hndbk. 654, W ashington, DC.
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ISTA. 2003. International rules for seed testing.Edition 2003. Int. Seed Test. Assoc.,Zurich, Switzerland.
Safford, L.O.; Bjorkbom , J.C.; Zasada, J.C. 1990.Betula papyrifera Marsh. Pages 158-171in R.M. Burns and B.H. Honkala, Tech.Coords. Silvics of North America, Vol. 2,Hardwoods. USDA, For. Serv., Agric.Hndbk. 654, W ashington, DC.
SAS. 2001. Statistical analysis system. SASInstitute Inc., Box 8000, Cary, NC.
W ang, B.S.P. 1973. Laboratory germinationcriteria for red pine (Pinus resinosa Ait.)seed. Proc. Assoc. Off. Seed Anal. 63:91-101.
W ang, B.S.P. 1987. The beneficial effects ofstratification on tree seed germination.Pages 56-75 in Proc. Nurserym en'sMeeting, Dryden, June 15-19, 1987. Ont.Min. Nat. Res., Toronto, ON.
W ang, B.S.P.; Ackerman, F. 1983. A newgermination box for tree seed testing.Can. For. Serv., Petawawa Nat. For. Inst.,Inform. Rep. PI-X -27.
Ben WangEmeritus Research ScientistNatural Resources CanadaCanadian Forest ServicePetawawa Research ForestP.O. Box 2000Chalk River, ON K0J 1J0
MAXIMIZING QUALITY OF Betula papyriferaSEED
W hite birch (Betula papyrifera Marsh.) seed is verylight and is winged making it impossible to removemost dead and empty seed using air aspiration. Aswell, the presence of the wings greatly adds to thevolume resulting in large containers being requiredto store large volumes of seed. If testing showedthe germination of a seed lot was poor (< 30%)then there was a tendency to discard the seed.This can be frustrating when effort and financialresources have been expended to collect andprocess the seed particularly if the collection wasmade from phenotypically superior trees. NationalTree Seed Centre staff noted the variation ingermination between seed lots collected over anumber of years. It was not until a number of seedsamples received from a cooperator wereprocessed and found to have higher than average1000-seed weights and high germination that aserious attempt was made to investigate a meansof improving the quality of seed lots. It was also
noted that m ost of the wings were missing fromthese samples.
The first attempt at removing empty seed involvedde-winging by gently hand rubbing in a light cottonbag and aspirating the rubbed sam ple. Thisworked to a certain extent but it was difficult tocontrol the air flow enough to prevent lighter filledseed from being removed and not removingheavier empty or partially filled seed. The SeedCentre routinely uses floatation in absolute ethanolto separate f illed from em pty seed in Larix, Picea,Pinus, Tsuga, and, more recently, Alnus. Thistechnique was tr ied on the de-winged birch seedfollowing aspiration. Several seed lots wereevaluated and paired testing (winged and de-winged + alcohol separation) conducted. Adram atic improvement in germination wasobserved for seed that had been de-winged andalcohol separated. After consulting the literature, itwas found that this technique was not new forbirch (Björkroth 1973).
An alcohol separation apparatus can be easilyconstructed. For small seed lots, a ring stand, ringsupport, glass or clear plastic funnel, clear tubing,clamp, strainer, and two 1000 ml beakers areneeded (Figure 1). Insert the end of a 20 cm longpiece of tubing onto the funnel. Place the funnelinto the ring support and attach to the ring stand.Adjust the height so the bottom of the tubing is justabove the strainer which sits on top of the beakerplaced on the base of the ring stand. Place theclamp near the bottom of the tubing. It pinches thetubing to not allow the alcohol to flow through untilthe seed have sunk . About 300 m l of alcohol arepoured into the funnel, the seed added, and stirredto allow heavy seed to sink. W hen the tubing is fu lland seed may have also accumulated on thebottom of the funnel the clamp is released causingthe seed and alcohol to flow into the strainer whichcollects the seed with the alcohol flowing throughinto the beaker. The clamp m ust be quick lyreplaced to prevent any of the floating seed beingwashed down with the sinkers. The seed in thestrainer are then imm ediately rinsed in cold (cool)running tap water for about 30 seconds thenplaced on paper toweling or fine mesh screen forair drying. The empty strainer is placed back ontop of the beaker and the clamp removed to allowthe seed that floated and alcohol to wash through.The beaker containing the alcohol is switched forthe empty beaker and the strainer containing theseed is placed on the empty beaker. The alcoholis then poured through the funnel to rem ove allremaining seed and collect them in the strainerafter which they are disposed of. For larger seedlots, a much larger version of this apparatus canbe constructed with the tubing becoming a largerdiameter colum n of clear PVC plastic orequivalent.
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Figure 1. Alcohol separation apparatus.
Effect of Immersion in Alcohol on SeedGermination
One obvious concern about using alcoholseparation was the potentia l impact of alcohol onthe health and long-term survival of the seed.Normally, seed is immersed in alcohol for up to 15seconds before being thoroughly rinsed in runningwater. A trial was set up using one seed lot. Seedwas immersed in absolute ethanol for periods of15, 30, 45, 60, 120, 180, 240, and 300 seconds.Following immersion the seed was rinsed inrunning water for 15 seconds and spread on papertowel to dry. After 24 hours, 4 replicates of 50 seedeach were placed on m oistened Kim pak inPetawawa germ ination boxes and placed in agermination cabinet for 21 days. Germinationconditions were diurnal cycles of 20°C anddarkness for 16 hours followed by 30°C and lightfor 8 hours. Hum idity was maintained at 85%.Although, at day 21, overall tota l high vigorgermination was not affected by duration ofimmersion in alcohol, there was a noticeableimpact at days 14 and 18 (Figure 2). At 14 days,there was a substantial decrease in germinationfor samples that had been in alcohol 60 secondsand longer. This same trend was obvious at day18 but had disappeared by day 21. In practice theseed are only exposed to alcohol for 10-15seconds before being thoroughly rinsed. Thereforeit is unlikely the alcohol affects the health of theseed.
Figure 2. Effect of duration in alcohol on germination of white birch seed after 14,18, and 21 days (from Daigle and Simpson 2002).
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Germination of Winged vs. De-winged +Alcohol Separated Seed
To further evaluate the improvem ent ingermination due to alcohol separation, anexperiment was set-up in 2002. Catkins werecollected from 3 or 5 trees from 5 populations.Following two months of air drying indoors, thecatkins were gently rubbed to break them apartand placed in an aspirator to separate the seedfrom the bracts , catkin axes, and other debris. Asample of seed was removed for germinationtesting. The remaining seed was placed in a cottonbag and gently rubbed to break off the wings. Thecontents were then dum ped onto a fine sieve toseparate the crushed wing debris from the seed.Following this phase, the seed was immersed inabsolute ethanol and stirred to ensure any heavyseed had an opportunity to sink. W hen most of theseed had completed sinking in the column (15seconds) the “sinkers” were collected in a strainerand rinsed under running tap water for 30seconds. The wet seed was spread on fine meshscreen trays and allowed to dry for several days atroom temperature. Germination tests were set upfollowing the sam e manner as described above.
Germination was assessed at 7, 14, and 21 days.Germ inants, classified as high vigor (cotyledonsgreen and separated with a well developed rad icleand upright hypocotyl), were removed at eachassessment time. At day 21 a count was made ofany low vigor germinants. Germ ination of wingedseed from individua l trees ranged from 0 to 73%while de-winged + alcohol separated seed rangedfrom 41 to 97%. There was clearly a substantialimprovement in germ ination due to the de-winging+ alcohol separation. There were large increasesin germination am ong individual trees as well as atthe population level. Initial seed quality variedconsiderably am ong populations with theproportion of im provement in germinationdependent upon initial seed quality (Figure 3). Forexample, winged seed from Clair and Coy Bk.populations had the lowest in itial germ ination butthe largest increase in germ ination after treatment.Another advantage of this treatment was the virtualelimination of low-vigor seed. Seed that floated inthe alcohol was not germination tested. Previousexperience showed that the germination of thisseed was low and any seed that did germinateexhibited low vigor.
Figure 3. Germ ination of white birch winged and de-winged + alcohol separated seed collected from individual trees in five populations.
Conclusions
Germination of white birch seed can besubstantially improved by removing the wings andfloating the seed in absolute ethanol to separate
the em pty and light filled seed from the heavierfilled seed. The process not only improvesgermination but also greatly reduces the volume ofseed to be stored. A trial showed there to be nodecline in total germination at 21 days for the
10
length of t ime the seed is immersed during atypical separation of up to 15 seconds.
References
Björkroth, G. 1973 Separation of b irch seed inliquids according to density. Proc. Int.Symp. Seed Processing, Vol. I. IUFROW ork Part. S2.01.06, Bergen, Norway, 9p.
Daigle, B.I.; Simpson, J.D. 2002. National TreeSeed Centre annual report 2001. Nat.Res. Can., Can. For Serv. Atlantic, 46 p.
Dale Sim pson and Bernard DaigleNatural Resources CanadaCanadian Forest ServiceAtlantic Forestry CentreP.O. Box 4000Fredericton, NB E3B 5P7E-mail: [email protected]
BOOK REVIEW
Vozzo, J.A. (Ed.) 2002. Tropical Tree SeedManual. USDA, For. Serv., Agric. Hndbk. 721, 899p.
Following is the Abstract from the manual. “The‘Tropical Tree Seed Manual’ is a one-volumereference manual for students, technicians, andscie ntists that provides com prehens ive,internationally compiled data about tropical trees.The emphasis is on species of the Americas;however, a number of tropical tree species fromother countries are also included. The manual isdivided into two parts. The first part consists ofnine chapters written by authorities on each area.The second part presents descriptions of 197botanically and economically important tropicaltree species. The manual is published in Englishand Spanish. It contributes to the academic andscientific comm unities by collating and organizinga wealth of internationally significant research andpractical data into one publication. It should beused with sim ilar references on seed technologyand handling to give students, technicians, andscientists a thorough understanding of tropical treeseeds.”
Part 1 consists of 236 pages and the followingchapters: Tropical Tree Seed Biology, Collection,Storage, Orthodox and Recalc itrant Seeds,Dormancy and Germination, Pathology, Ecology,Ethnobotany, and Notes on Tropical Dendrology.The Seed Biology chapter is liberally illustratedusing color diagrams and photographs. Althoughthe focus is intended toward tropical tree speciesthere is much that has been gleaned from theliterature on temperate species. There is an
impressive list of references with about 2 400citations. This in itself is a valuable resource asmost chapter authors have reviewed the literaturequite extensively. I highly recomm end this book(manual) as a valuable addition to your bookshelf.The best means of enquiring about obtaining ac o p y i s to e - m a i l t h e e d i t o r a t :[email protected]
Dale Simpson
HARDW OO D SEED TREATM ENTS INQUÉBEC
Each year in Québec, an average of one millionhardwood seedlings of 15 different species arereforested. To produce this million seedlings, anaverage of 245 hl of seeds are harvested eachyear. This corresponds to about 80 seed lots of the15 species. Most of the hardwood seeds areharvested in southern Québec, in natural stands.The harvesting season depends on when the fruitreaches maturity. For exam ple, silver maple (Acersaccharinum), red maple (A. rubrum), and whiteelm (Ulmus americana) seeds are harvested in thespring while those of other species in the fall. Allthe seeds are sent to the Centre de semencesforestières de Berthier (75 km east of Montreal)where they undergo processing and germinationtesting.
Regardless of their final destination, all theseedlings are produced at the Berthier nursery.Seedlings are grown in containers or as bareroot.The major species are yellow birch (Betulaalleghaniensis), red oak (Quercus rubra), sugarmaple (Acer saccharum) and white ash (Fraxinusamericana).
Seed Stratification Requirements by HardwoodSpecies
Some hardwood seeds are dorm ant and fa il togerm inate after processing when placed underconditions considered adequate for germination.Depending on the species, dormancy isphysiological and / or physical. The degree ofdormancy can vary according to the collection site.
Seed of each hardwood species requires a specificstratification method to overcom e the dormancy.Furthermore, within the sam e species, seed lotscan require different stratification periods toovercome dorm ancy. As the stratificationperiods differ for each seed lot, we have toundergo preliminary tests to determine theproper duration for further operationalstratification.
The stratification methods have been adapted fromthe few references on this subject or developed in
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Québec. The methods used in Québec for thedormant hardwood seeds grown in containers aredescribed in Table 1. For seedlings cultivatedbareroot, stratification conditions can differ. Somespecies are sown non- stratified and thestratification occurs naturally in the seedbed.
Others are stratified using a method that can differfrom the one used for container production. Thestratification methods used for hardwood seedsgrown for bareroot production are described inTable 2.
Table 1. Stratification methods for hardwood seeds grown in containers
Common nameLatin name
Type of dormancy Stratification method
Sugar mapleAcer saccharum
Physiological andphysical
Soak seeds in water for 14 days at 3°C,Drain excess water,Stratify in cold (3°C), humid, anaerobic conditions without medium for 3 to 5 weeks, depending on germination test results, until radicle emergence.
Red mapleAcer rubrum
Physiological andphysical
Soak seeds in water for 2 days at 20°C,Drain excess water.
Silver mapleAcer saccharinum
None Not required
Yellow birchBetula alleghaniensis
Light Put seeds in a net between 2 layers of humid peat moss at 3°C for 21 days.
W hite birchBetula papyrifera
None Not required
W hite ashFraxinus americana
Deep physiologicaland physical
Soak seeds in water for 2 days at 20°C,Drain excess water,Put seeds in a mix of humid peat and sand in a bag (25 l),W arm stratify (20°C) for 4 weeks,Cold stratify (3°C) for 18 to 22 weeks, depending on germination test results.
Green ashFraxinus pennsylvanica
Physiological andphysical
Soak seeds in water for 2 days at 20°C,Drain excess water,Put seeds in a mix of humid peat and sand in a bag (25 l),Cold stratify (3°C) for 19 to 22 weeks, depending on germination test results.
Black cherryPrunus serotina
Physiological andphysical
Soak seeds in water for 2 days at 20°C,Mix seed with moist peat moss and sand and stratify in polyethylene bags for 17 to 19 weeks, Alternate cold and warm stratification: 2 weeks at 20°C, 6 weeks at 3°C, 1 week at 20°C, 8 to 10 weeks at 3°C depending on germ ination test results.
Red oakQuercus rubra
Light Store seeds in polyethylene bags (4 mil; 25 l) at 3°C without medium,4 weeks before sowing time, soak seeds in water for 2 days at 20°C,Drain excess water, Put seeds into a polyethylene bag (4 m il) at 3°C until radicle emergence.
American basswoodTilia americana
Very deepphysiological andphysical
Soak seeds in water for 2 days,Drain excess water,Put seeds in a mix of hum id peat and sand in a bag at 3°C for 26 to 30 weeks (poor germination).
W hite elmUlmus americana
None Not required
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Table 2. Stratification methods for hardwood seeds grown for bareroot production
Common nameLatin name
Type of Dormancy Stratification method
Sugar mapleAcer saccharum
Physiological andphysical
Soak seeds in water for 14 days at 3°C,Drain excess water,Stratify in cold (3 °C) and humid condition without medium and in anaerob ic conditions for 2 to 4 weeks before radicle emergence.
Bitternut hickoryCarya cordiformis
Physiological andphysical
Sow in seedbed in fall.
W hite ashFraxinus americana
Deep physiological andphysical
Same as container production.
Black walnutJuglans nigra
Physiological andphysical
Put de-husked seeds into a polyethylene bag (4 mil; 25 l) at 3°C without medium during winter.
Black cherryPrunus serotina
Physiological andphysical
Same as container production.
W hite oakQuercus alba
None Sow in seedbed in fall.
Red oakQuercus rubra
Light physiological andphysical
Sow in seedbed in fall.
Conclusion
The production of hardwood seedlings is verydemanding:
1 Each species requires a specificstratification method and the duration of itmust be evaluated after the collection ofeach seed lo t be fore beginningoperational stratification.
2 Cultivation and cultural requirements ofthe seedlings are specific and different foreach species.
3 Hardwoods have such a great value(aesthetic and economic) that theinvestment in testing and cultivating isjustified. It is essential to maintain acertain degree of biodiversity of the south-western forest of Québec.
For more information, visit the ministry web site:http://www.m rn.gouv.qc.ca/english/forest/quebec/quebec-system-managem ent-plants .jsp ( inEnglish)http://www.mrn.gouv.qc.ca/forets/entreprises/entreprises-semences.jsp (in French, m ore detail)
Michèle Bettez1 and Fabienne Colas2
1 Forêt QuébecCentre de semences forestières de Berthier1690, chem in Grande-CôteBerthier, Qc J0K 1A0E-mail: [email protected]
2 Forêt QuébecDirection de la recherche forestière2700, rue EinsteinSainte-Foy, Qc G1P 3W 8E-mail: fabienne.colas@m rn.gouv.qc.ca
HARDWOOD SEED STORABILITY REVISITED
In News Bulletin #28 I presented data onhardwood seed storability1. This information hasbeen updated and it seem s timely to report theresults in keeping with the theme of this NewsBulletin. Data are available on a total of 61hardwood seed lots of the following species: greenalder (Alnus crispa), red alder (Alnus rubra), whitebirch (Betula papyrifera), and trembling aspen(Populus tremuloides) (Table 1). Deteriorationrates were estimated for each seed lot byquantifying the change in germination duringstorage:
Deterioration Rate = (Current GC – Initial GC) /(time between GC tests)
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Table 1. Deterioration rates of hardwood species in storage at the BCMoF Tree Seed Centre
Species # Seed lots
Deterioration rate
ÎGC/yearMaximum
age (years) Initial GC range (%)
Green Alder 10 +0.33 7.3 24 – 86
Red Alder 18 +0.83 8.5 20 – 90
W hite Birch 24 +0.39 21.0 3 – 92
Trembling Aspen 9 -3.63 6 41 – 96
It is interesting to note that very little has changedin the relative deterioration rates of thesehardwood species. Trembling aspen is still thefastest deteriorating species, although the currentestim ate of -3.63%/year is much less than the -8.6% estimated in 1998. The current rate is basedon a larger dataset and longer s torage durationsproviding more confidence in the estimate. Therate is still only based on nine seed lots and thesevaried tremendously in deterioration rates from 0.0to -18.0%/year. It is interesting to note thatalthough there exists a large range in initialgermination, trembling aspen actually has thesmallest range of the four hardwood species.
The remaining species had relatively similardeterioration rates and, as was the case in 1998,the species tended to increase in GC slightlyduring storage. This is unexpected and it isuncertain whether it is: 1) just an artifact of thedata, 2) an indication of dormancy release duringlong-term storage (heresy some would cry!) as allspecies are tested dry, or 3) other factors notaccounted for as being important (i.e. light). It isunlike ly that I am going to resolve this question,but it is comforting that there is very little change ingerm ination over time for these three species.
__________________________
1 Note that in 1998 a decreased GC was indicatedby a positive deterioration rate, but currentmethodology has the sign of the deterioration rate
indicating the direction of ÎGC. This method ofpresentation appears to be m ore logical.
Dave KoloteloBC Ministry of ForestsTree Seed Centre18793 - 32nd AvenueSurrey, BC V4P 1M5E-mail: Dave.Kolotelo@gem s7.gov.bc.ca
SEED TESTING MANUALS
Both the Association of Seed Analysts (AOSA)and International Seed Testing Association (ISTA)have published new and updated seed testingmanuals.
The AOSA “Rules for Testing Seeds” manual is in3-ring binder format making it easy to add andremove pages and insert any additionalinformation. The manual costs $55 US plusshipping and handling. You can contact JaniceOsburn at [email protected] for additionalinformation.
In the past, ISTA has published a completemanual “International Rules for Seed Testing”every three years following their Congress duringwhich changes to the Rules were presented, votedon, and approved. The ‘new’ complete set of theInternational Rules for Seed Testing includes thefollowing two separate publications: InternationalRules for Seed Testing, Edition 2003 and Annexeto Chapter 7, Seed Health Testing Methods. TheEdition 2003 is in a binder format. Each year,updates, including additions or replacements ofexisting pages, will be published and can beseparately inserted into the binder. The completeset costs ~ $215 US. You can contact AgnesHegedüs at [email protected] for furtherinformation.
Dale Simpson
14
UPCOMING MEETINGS
B.C. Seed Orchard Association Annual MeetingJune 17-18, 2003 Vernon, BCContact: George Nicholson (250) 546-2293GW [email protected]
Western Forest Genetics Association AnnualMeeting Genetics, Genomics and AdaptationJuly 28-31, 2003 W histler, BCwww.genetics.forestry.ubc.ca/wfga2003 for moreinformation
IUFRO Seed Physiology & TechnologyResearch Group Tree Seed Symposium August 10-14, 2003 Athens, GeorgiaUSAContact: Gary [email protected] orwww.ntsl.fs.fed.us for more information
XII World Forestry CongressForests , Source of LifeSeptember 21-28, 2003 Quebec Citywww.wfc2003.org for more information
Forest Nursery Association of BC 23rd Annual MeetingS.O.S. (Seedlings/Objectives/Service)September 22-25, 2003 Courtenay, BCContact: Siriol Paquet (250) [email protected]
ISTA Forest Tree and Shrub Seed Com mitteeWorkshopOctober 20-25, 2003 Prague, Czech
RepublicContact: Zdenka [email protected]
Seed Ecology 2004Tentatively April 29-May 4, 2004
Rhodes Island,Greece
Contact: Costas [email protected]
ISTA Seed Symposium 2004 27th Congress“Towards the Future in Seed Production,Evaluation and Improvement”May 13-24, 2004 B u d a p e s t ,
Hungarywww.seedtest.org for more information
Molecular Aspects of Germination andDormancyMay 24-25, 2004 W a g e n i n g e n ,
The Netherlands
and
Third International Symposium on PlantDormancyMay 25-28, 2004 W a g e n i n g e n ,
The Netherlandswww.css.cornell.edu/ISSS/isss.htm for moreinformation
If you know of a m eeting that would interest thereadership, please forward the information to theChairperson or Editor.
SELECTED REFERENCES – HARDWOODSEED
More papers from Dave’s files . Mostly specificstudies and not many reviews. Does anyone havesome good reviews of hardwood seed biology? intheir library that they would like to share with ourreaders? (EDITORS NOTE: see Flores 2002)
Anella, L.B.; Whitlow, T.H. 1998. Germination ofAcer rubrum seeds collected from wet anddry habitats. Seed Sci. Technol. 26: 755-762.
Babenko, L.M .; Musatenko, L.I. 1998. Proteinsynthesis in seeds of Acer tataricum L.during dormancy breaking. Russian J.Plant Physiol 45: 96-100 (translated fromFiziologiya Rastenii 45(1): 112-116.
Banerjee, S.M .; Creasey, K.; Douglas Gertzen, D.2001. Native W oody Plant SeedCollection Guide for British Columbia. BCMin. For., Tree Imp. Br. 146 p.
Bevington, J.M.; Hoyle, M.C. 1981. Phytochromeact ion during prech i ll ing inducedgermination of Betula papyrifera Marsh.Plant Physiol. 67: 705-710.
Bjorkroth, G. 1973. Separation of birch seeds inliquids according to density. in Proc.IUFRO Int. Symp. Seed Processing,Bergen, Norway, Vol.1, Paper No. 3. 9 p.
Black, M.; Wareing, P.F. 1955. Growth studies inwoody species. VII. Photoperiodic controlof germ ination in Betula pubescens Ehrh.Physiol. Plant. 8: 300-316.
Black, M.; W areing, P.F. 1959. The role ofgermination inhibitors and oxygen in thedormancy of the light-sensitive seed ofBetula spp. J. Exp. Bot. 10(28): 134-145.
Boes, T.K.; Strauss, S.H. 1994. Floral phenologyand morphology of black cottonwood,Populus trichocarpa (Salicaceae). Am. J.Bot. 81: 562-567.
Blanche, C.A.; Elam , W .W .; Hodges, J.D. 1990.Accelerated aging of Quercus nigra seed:biochemical changes and applicability asa vigor test. Can. J. For. Res. 20: 1611-1615.
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Bonner, F.T. 1970. Hardwood seed collection andhandling. Pages 53-63 in Proc. Silviculturea n d M a n a g e m e n t o f S o u t h e rnHardwoods. Louisiana State Univ. 19 th
Ann. For. Symp., Louisiana State Univ.Press. 145 p.
Bonner, F.T. 1971. Chem ical contents of southernhardwood fruits and seeds. USDA, ForServ., South. For. Exp. Sta., Res. NoteSO-136. 3 p.
Bonner, F.T. 1973. Timing collections of samarasof Fraxinus pennsylvanica Marsh. in thesouthern United States. in Proc. IUFROInt. Symp. Seed Processing, Bergen,Norway, Vol. 1, Paper No. 4. 7 p.
Bonner, F.T. 1973. Storing red oak acorns. TreePlant. Notes 24: 12-13.
Bonner, F.T. 1974. Tests for vigor in cherrybarkoak acorns. Proc. Assoc. Off. Seed Anal.64: 109-114.
Bonner, F.T. 1976. Maturation of shumard andwhite oak acorns. For. Sci. 22: 149-154.
Bonner, F.T. 1994. Predicting seed longevity forfour forest tree species with orthodoxseeds. Seed Sci. Technol. 22: 361-370.
Carl, C.M. Jr. 1976. Effect of separation in n-pentane on storability of sugar mapleseeds. USDA., For. Serv., Northeast. For.Exp. Sta., Res. Note NE-218. 3 p.
Carl, C.M. Jr.; Yawney, H.W . 1977. Fall versusspring sowing of sugar maple seed in anursery. Tree Plant. Notes 28(3-4): 24-26.
Carl, C.M. Jr. 1982. The propagation and plantingof sugar maple: seed collection andhandling. Pages 47-52 in Sugar MapleResearch: Sap Production, Processingand Marketing of Maple Syrup. USDA,For. Serv., Northeast. For. Exp. Sta., Gen.Tech. Rep. NE-72.
Carl, C.M. Jr.; Yawney, H.W. 1966. Fourstratification media equally effective inc o n d i ti o n in g s u g a r m a p l e s e edgermination. Tree Plant. Notes 77: 24-28.
Carl, C.M. Jr.; Snow, A.G. 1971. M aturation ofsugar maple seed. USDA, For. Serv.,Northeast. For. Exp. Sta., Res. Pap. NE-217. 9 p.
Dey, D.; Buchanan, M. 1995. Red oak (Quercusrubra L.) acorn collection, nursery cultureand direct seeding: a literature review.Ont. Min. Nat. Res., For. Res. Inform .Pap. No. 122. 46 p.
Dum broff, E.B.; W ebb, D.P. 1970. Factorsinfluencing the stratif ication process in
seeds of Acer ginnala. Can. J. Bot. 48:2009-2015.
Farm er, R.E.; Cunningham, M. 1981. Seeddormancy of red maple in eastTennessee. For. Sci. 27: 446-448.
Farm er, R.E.; Goelz, J.C. 1984. Germinationcharacter is t ics o f red maple innortheastern Ontario. For. Sci. 30: 670-672.
Farrant, J.M .; W alters, C. 1998. Ultrastructural andbiophysical changes in developingembryos of Aesculus hippocastanum inrelation to the acquisition of to lerance todrying. Physiol. Plant. 104: 513-524.
Finch-Savage, W .E.; Clay, H.A.; Dent, K.C. 2002.Seed maturity affects the uniformity ofcherry (Prunus avium L.) seed responseto dormancy-breaking treatments. SeedSci. Technol. 30: 483-497.
Flores, E.M . 2002. Seed biology. Pages 13-118 inJ.A. Vozzo, ed. Tropical Tree SeedManual. USDA, For. Serv., Agric. Hndbk.721. 899 p.
Fung, M.Y.; Hamel, B.A. 1993. Aspen seedcollection and extraction. Tree Plant.Notes, Summer 98: 100.
Haeussler, S.; Tappeiner II, J.C. 1993. Effect oflight environment on seed germination ofred alder (Alnus rubra). Can. J. For. Res.23: 1487-1491.
Janerette, C.A. 1979. Cold soaking reduces thestratification requirem ent of sugar mapleseeds. Tree Plant. Notes 30(2): 3.
Janerette, C.A. 1979. Seed dormancy in sugarmaple. For. Sci. 25: 307-311.
Jensen, M.; Eriksen, E.N. 2001. Development ofprimary dormancy in seeds of Prunusavium during m aturation. Seed Sci.Technol. 29: 307-320.
Joseph, H. 1929. Germination and vitality of birchseeds. Bot. Gaz. 87: 127-151.
Junttila, O. 1970. Effects of stratification,gib be re llic ac id a nd ge rm inatio ntemperature on the germination of Betulanana. Physiol. Plant. 23: 425-433.
Linteau, A. 1948. Factors affecting germ inationand early survival of yellow birch (Betulalutea Michx.) in Quebec. For. Chron. 24:27-86.
Muller, C.; Bonnet-Masimbert, M. 1989. Storage ofnon-dormant hardwood seeds: newtrends. Ann. Sci. For. 46 suppl. 92s-94s.
16
Muller, C.; Laroppe, E.; Bonnet-Masimbert, M.1999. Further developments in theredrying and storage of prechilledbeechnuts (Fagus sylvetica L.): effect ofseed moisture content and prechillingduration. Ann. For. Sci. 56: 49-57.
Peroni, P. 1995. Field and laboratoryinvestigations of seed dormancy in redmaple (Acer rubrum L.) from the NorthCarolina Piedmont. For. Sci. 41: 378-386.
Pite l, J.A.; W ang, B.S.P.; Cheliak, W .M. 1984.Improving germination of hop-hornbeamseeds. Can. J. For Res. 14: 464-466.
Pritchard, H.W .; Steadman, K.J.; Nash, J.V.;Jones, C. 1999. Kinetics of dormancyrelease and the high temperaturegermination response in Aesculushippocastanum seeds. J. Exp. Bot. 50:1507-1514.
Redmond, D.R.; Robinson, R.C. 1954. Viabilityand germination of yellow birch. For.Chron. 30: 79-87.
Suszka, B.; Muller, C.; Bonnet-Masimbert, M.1996. Seeds of forest bradleaves fromharvest to sowing. INRA, Paris, France.(Translated by A. Gordon) 295 p.
Taylorson, R.B. 1991. Inhibition of germ ination inAmaranthus albus seeds by prolongedirradiation: a physiological basis. SeedSci. Res. 1: 51-56.
Toth, J.; Garrett, P.W. 1989. Optimumtemperature for stratification of severalmaple species. Tree Plant. Notes 40: 9-12.
Tremblay, M.F.; Maufette,Y.; Bergeron, Y. 1990.Effects of stratification, temperature, andlight on germination of Acer rubrum . Bull.Ecol. Soc. Amer. 71: 347-348.
Tremblay, M.F.; Maufette,Y.; Bergeron, Y. 1995.Germination responses of northern redmaple (Acer rubrum) populations. For.Sci. 42(2): 154-159.
Vanstone, D.E. 1978. Basswood (Tiliaamericana) seed germ ination. Proc. Int.Plant Prop. Soc. 28: 566-570.
Vanstone, D.E.; La Croix, L.J. 1975. Embryoimmaturity and dormancy of black ash. J.Am. Soc. Hort. Sci. 100: 630-632.
Villiers, T.A. 1971. Cytological studies indormancy: I. Embryo maturation duringdormancy in Fraxinus excelsior. NewPhytol. 70: 751-760.
Villiers, T.A. 1972. Cytological studies indorm ancy: II. Pathological age ingchanges during prolonged dormancy andrecovery upon dormancy release. NewPhytol. 71: 145-152.
Villiers, T.A. 1972. Cytological studies indormancy: III. Changes during low-temperature dormancy release. NewPhytol. 71: 153-160.
W ang, B.S.P. 1965. Seedbed, canopy andmoisture effects on growth of yellow birchseedlings. For. Chron. 41: 106-107.
W ang, B.S.P.; Haddon, B.D. 1978. Germination ofred maple seed. Seed Sci. Technol. 6:785-790.
W ang, B.S.P.; Pitel, J.A. 1991. Germination ofdormant tree and shrub seeds. Pages 6-1– 6-16 in A.G. Gordon, P. Gosling, B.S.P.W ang, eds. Tree and Shrub SeedHandbook. Int. Seed Test. Assoc., Zurich,Switzerland.
W ebb, D.P. 1974. Germination control of stratifiedsugar maple seeds. For. Chron. 50: 112-113.
W ebb, D.P.; Dum broff, E.B. 1969. Factorsinfluencing the stratification process inseeds of Acer saccharum. Can. J. Bot.47: 1555-1563.
W ebb, D.P.; W areing, P.F. 1972. Seed dormancyin Acer pseudoplatnus L.: the role of thecovering structures. J. Exp. Bot. 23(76):813-829.
W ebb, D.P.; W areing, P.F. 1972. Seed dormancyin Acer : endogenous germ inationinhibitors and dorm ancy in Acerpseudoplatnus L. Planta 104: 115-125.
W ebb, D.P.; Van Staden, J.; W areing, P.F. 1973.Seed dormancy in Acer: changes inendogenous cytokinins, gibberellins andgermination inhibitors during the breakingof dormancy in Acer saccharum Marsh. J.Exp. Bot. 24(78): 105-116.
W ebb, D.P.; Van Staden, J.; W areing, P.F. 1973.Seed dormancy in Acer: Changes inendogenous germ ination inhibitors,cytokinins, and gibberellins during thebreak ing o f dor m an cy i n Acerpseudoplatanus L. J. Exp. Bot. 24(81):741-750.
W eiss, F. 1926. Seed germination in grey birch,Betula populifolia. Am. J. Bot. 13: 737-742.
W ilson, B.F.; Hibbs, D.E.; Fischer, B.C. 1979.Seed dormancy in striped maple. Can. J.For. Res. 9: 263-266.
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Yawny, H.W .; Carl, C.M. Jr. 1974. Storagerequirements for sugar maple seeds.USDA, For. Serv., Northeast. For. Exp.Sta., Res. Pap. No. NE-298. 7 p.
EDITOR’S NOTE: Sincere appreciation isextended to Ben Wang for providing additionalreferences to this list.
RECENT PUBLICATIONS
Bilir, N.; Kang, K.S.; Ozturk, H. 2002. Fertilityvariation and gene diversity in clonal seedorchards of Pinus brutia, Pinus nigra andPinus sylvestr is in Turkey. Silvae Genet.51: 112-115.
Cooke, J.; Cooke, B.; Gifford, D. 2002. Loblollypine seed dorm ancy: constraints togermination. New For. 23: 239-256.
David, A. 2002. Germination percentage andgermination speed of European larch(Larix decidua Mill.) seed after prolongedstorage. North. J. Appl. For. 19: 168-170.
Demelash, L.; Tigabu, M.; Oden, P.C. 2002.Separation of empty and dead-filled seedsfrom a seed lot of Pinus patula with IDStechnique. Seed Sci. Technol. 30: 677-681.
Escudero, A.; Perez-Garcia, F.; Luzuriaga, A.L.2002. Effects of light, temperature andpopulation variability on the germination ofseven Spanish pines. Seed Sci. Res. 12:261-271.
Gil, L.; Climent, J.; Nanos, N.; Mutke, S.; Ortiz, I.;Schiller, G. 2002. Cone morphologyvariation in Pinus canariensis Sm. PlantSystem. Evol. 235: 35-51.
Hannerz, M.; Almqvist, U.; Hornfeldt, R. 2002.Timing of seed dispersal in Pinussylvestr is stands in central Sweden. SilvaFenn. 36: 757-765.
Hilli, A.; Tillman-Sutela, E.; Kauppi, A. 2003.Germination of pretreated Scots pineseeds after long-term storage. Can. J.For. Res. 33: 47-53.
Hussain, M.; Kubiske, M.E.; Connor, K.F. 2001.Germination of CO2-enriched Pinus taedaL. seeds and subsequent seedling growthresponses to CO2 enrichment. Function.Ecol. 15: 344-350.
Kang, K.S. ; E l -Kassaby, Y.A.. 2002.Considerations of correlated fertilitybetween genders on genetic diversity: thePinus densiflora seed orchard as a m odel.Theor. Appl. Gen. 105: 1183-1189.
Kantorowicz, W . 2002. Effect of forst 5-yearsstorage temperature on vitality of Norwayspruce [Picea abies (L.) Karst.] seedsfrom different trees. [In Polish, Englishsummary] Prace Inst. Bas. LeÑ., A, 2002,3(938): 19-41.
Noble, R.E. 2002. Effects of UV-irradiation onseed germination. Sci. Tot. Environ. 299:173-176.
Ocamb, C.M.; Juzwik, J.; Martin, F.B. 2002.Fusarium spp. and Pinus strobusseedlings: root disease pathogens andtaxa associated with seed. New For. 24:67-79.
Phartyal, S.S.; Thapliyal, R.C.; Koedam, N.;Godefroid, S. 2002. Ex situ conservationof rare and valuable forest tree speciesthrough seed-gene bank. Curr. Sci. 83:1351-1357.
Schröder, T.; Kehr, R.; Hüttermann, A. 2002. Firstr e p o r t o f t h e s e e d - p a t h o g e nGeniculodendron pyriforme, the imperfectstate of the ascomycete Caloscyphafulgens, on imported conifer seeds inGermany. For. Path. 32: 225-230.
Takos, I.; Merou, T. 2001. Effects of storageconditions and seed treatment ongermination of Cedrus deodora LOUD.and C. libani RICH. Silvae Genet. 50: 205-208.
Za»�sk i, A. 2003. The effect of different methods ofNorway spruce seed extraction on theirvitality and predispos ition to long-termstorage. [In Polish, English sum mary]Prace Inst. Bad. LeÑ., A, 2003, 1(948) 7-22.
Zeng, Y.; Raimondi, N.; Kermode, A.R . 2003. Roleof AB13 homologue in dormancymaintenance of yellow-cedar seeds in theactivation of storage protein and Em genepromoters. Plant Mol. Biol. 51: 39-49.
