Flowering Sequence and the Ordering of Impermeability Breakdown in Seed of Subterranean Clover (Trifolium subterraneum L.)

The pattern of breakdown of seed coat impermeability of seedwithin the burrs of two cultivars of subterranean clover (Trifoliumsubterraneum L.) was closely associated with relative differencesin flowering sequence within the inflorescence. The patternof seed weight variation showed very little relationship withthe pattern of breakdown, while that for seed moisture contentshowed no relationship. Within a burr it was almost invariably the seed which developedfrom the latest flower within the inflorescence which was thefirst to become permeable. An ordering of the timing of breakdownwas evident only within the burr; there was no evidence fora pattern of breakdown of impermeability between the differentburrs along the runner. Trifolium subterraneum L., subterranean clover, seed coat impermeability, seed weight, seed moisture, hardseededness     

Changes in Trifolium arvense Seed Quality Following Alternating Temperature Treatment using Liquid Nitrogen

The effects of alternating temperatures, using liquid nitrogen(–196°C) as the low temperature phase, on Trifolium arvense L.seed quality was investigated. Treatment reduced hardseedednesswith the seeds exhibiting a linear increase in the probit ofgermination with the logarithm of the number of alternatingtemperature cycles. Germination levels equal to ‘chipped’controls were achieved after four cycles or more, dependingon the initial depth of hardseededness, and the response wasunaffected by either the rate of cooling or the rate of warming. Imbibition time was reduced with increasing alternating temperaturecycles. Resealing experiments identified the main area of wateruptake as the lens, and SEM showed that deepening of alreadypresent cracks may be important in removing hardseededness.Pre-treatment of seeds with alternating temperatures predisposesthe seeds to subsequent damage by sulphuric acid treatment,but not by impaction. Stress effects were not restricted to the seed coat surfaceas between 10 and 20 % of seeds treated for 3–15 cyclesdeveloped into abnormal seedlings with detached cotyledons.Seed vigour is also reduced as treatment leads to contractionof the temperature response curve for germination. The resultshave implications for the cryopreservation of papilionoid legumeseeds as a means of genetic conservation. Trifolium arvense, Hare's foot, hardseededness, quantal response, cryopreservation, liquid nitrogen     

Cryopreservation for Seedbanking of Australian Species

Recent studies have indicated that a large number of nativeAustralian species can be stored in liquid nitrogen using relativelystraightforward methods. Furthermore, it is estimated that seedfrom at least 40% of the rare and endangered species of WesternAustralia could be maintained through use of these cryopreservationtechniques. However, before cryopreservation of seed of Australianspecies can be implemented as a routine technique, physicaland chemical properties of seed must be studied. This studyhas shown that successful cryopreservation of seed could beinfluenced singly or by a combination of hardseededness, moisture,lipid content, fatty acid and amino acid composition. The studyalso details the role of in vitro methods for determining seedviability/recovery of species that are either damaged by liquidnitrogen or are difficult to germinate.Copyright 1994, 1999Academic Press Seed, cryopreservation, lipid, fatty acid, amino acid, Australian species     

Interrelations Between Seeds and Associated Fruiting Structures During Their Development in Trifolium subterraneum L.

Developing burrs of T. subterraneum (cv. Daliak) were subjectedto dark and light treatments in experiments conducted in a controlledtemperature glasshouse with day/night air temperatures of 18/13°C. Post fertilization development of burr components wasfollowed and the effect of removal of seeds or sterile calyoeson the development of the remaining burr components studied. Peduncle elongation took place mainly between days 0 (anthesis)and 7, when the burr would normally have buried. Seed developmentwas completed by day 42. Pod walls attained near maximum weightat about day 22. The perianth increasd in weight between days12 and 22 due to enlargement of the calyx. Sterile calyces wereprduced continuously until day 42. The pattern of burr develompentwas similar in both dark and light, but the weight of the maincomponents were considerably reduced in the light treatment. Normal peduncle development depended on the presence of at leastone seed in the inflorescence. Pod walls did not develop, neitherdid the perianth enlarge unless these structures were associatedwith a developing seed. In the absence of seeds fewer sterilecalyces were produced in the dark treatment and fewer stillwere produced in the light, indicating a direct inhibitory effectof light on the production of sterile calyces. Within matureburrs the weight of pod walls and sterile calyces was closelyrelated to the weight of seeds. Removal of sterile calyces reducedseed production but interpretation of this effect is not clear. Trifolium subterraneum L., fruit development, seed production     

Self-incompatibility, Inbreeding Depression and Crossing Potential in Five BrazilianPleurothallis (Orchidaceae) Species

Intra- and interspecific experimental pollinations were madeto determine the mating systems and the interspecific crossingpotential in individuals from 24 populations of five Pleurothallisspecies. Pleurothallis johannensis, P. ochreata and P. teresshow weak or partial self-incompatibility while P. adamantinensisand P.fabiobarrosii are more strictly self-incompatible. Wefound no differences in fruit set between intra- and interpopulationintraspecific crosses, and there was no correlation betweenfruit set and genetic variability or inbreeding in these species.All species are interfertile and showed no correlation betweengenetic similarity and crossing potential. We scored fruitsfor seed viability and observed a strong inbreeding depressionin all populations; however, there was no difference in seedviability among intrapopulation, interpopulation intraspecificand interspecific cross-pollinations. These species are pollinatedby flies with a behavioural pattern that facilitates self-pollination.Self-incompatibility and inbreeding depression are apparentlyimportant in the maintenance of the unusually high levels ofgenetic variability found in these species. As generally observedin other orchid species, barriers to hybridization between thesePleurothallis species are at the level of pollination. Copyright2001 Annals of Botany Company Pleurothallis, Orchidaceae, mating system, self-incompatibility, inbreeding depression, fruit set, seed set, polyembryony, interspecific compatibility     

The Role of the Lens in Seed Imbibition and Seedling Vigour of Sesbania punicea (Cav.) Benth. (Leguminosae: Papilionoideae)

Seeds of Sesbania punicea (Cav.) Benth. are largely impermeable,and the natural, low, percentage which germinate are permeableat the lens. Scarifying seed in acid stimulates germinationand causes various types of damage to the testa, including thelens. Placing seeds in boiling water stimulates germinationby rendering the seeds permeable at the lens. Seeds were mechanicallyscarified at precise sites on the testa to assess influenceof the site and degree of damage on germination. Results indicatethat both the site of initial water entry and the rate of waterentry are important in determining seed and seedling vigour.Damaging the lens is more effective in stimulating germinationand reducing seedling abnormalities than complete excision ofthe lens. This effect can be reversed if seeds from which thelens was excised are allowed to imbibe gradually in inert osmotica.The leguminous lens thus acts as the site of initial water entryand regulates the rate of water uptake, thereby increasing seedand seedling vigour. Sesbania punicea (Cav.) Benth., hardseededness, lens, seed germination, imbibition damage, seedling vigour     

Leaf Abscission in Varieties of Phaseolus vulgaris (L. ) and Glycine max (L. ) Merrill/emdash a--Correlation with Propensity to Produce Adventitious Roots

In field trials of Phaseolus vulgaris large differences wereobserved between varieties in the rate at which the leaves abscised.Similar differences were found in the rate of decline of thechlorophyll content of excised leaf discs. A grafting experimentshowed that the differences in leaf abscission depended on thegenotype of the scion and on that of the rootstock. Scion andstock effects of each genotype were similar, and additive. Rootstock/scioncombinations which conferred enhanced leaf retention producedgreater yields of seed and of seed nitrogen. When shoots ofdelayed-senescence genotypes of P. vulgaris were held in waterthey produced more adventitious roots than did shoots of rapid-senescencegenotypes. This relationship between senescence pattern andadventitious rooting was also observed among varieties of Glycinemax, and between isogenic lines of G. max differing in the leafabscission alleles Ab/ab. These results are discussed in relationto current theories of leaf senescence, abscission, and theproduction of yield.     

The Low-moisture-content Limit to the Negative Logarithmic Relation Between Seed Longevity and Moisture Content in Three Subspecies of Rice

The lower limit to the negative logarithmic relation betweenseed longevity and moisture content was determined in threesubspecies of rice (Oryza satwa L.) by storing seeds of fivecultivars at 65 °C with 11 different moisture contents (1.5–15.3%f. wt) for various periods up to 150 d and then testing forgermination. The estimates of the low-moisture-content limit(m_c) were 4.3% for subsp. indica, 4.4% for subsp. japonica,and 4.5% for subsp. javanica. These moisture contents were inequilibrium with 10.5—12.0% r.h. No significant effectof moisture content between 1.5% and m_c on longevity was detected(P > 0.05), while between m_c and 15.3% there were negativelogarithmic relations between longevity and moisture content.There were no significant differences in the relations betweenlongevity and moisture either above or below m_c between thetwo japonica cultivars or between the two javanica cultivars(P > 0.10). There was also no significant difference in theslope of the negative logarithmic relation between longevityand moisture above m_c among the three subspecies (P > 0.25).However, there were significant differences in the standarddeviation of the frequency distribution of seed deaths in timeat any one moisture content, both above and below m_c; this isa measure of seed longevity which is independent of pre-storageenvironment, and the differences observed show that there aregenetically determined differences in longevity among the threesubspecies (P < 0.005), indica being the longest and japonicathe shortest lived. The results provide no evidence for intra-specificvariation in m_c and support the view that the maximum seed storagemoisture content which provides the maximum longevity is thatwhich is in equilibrium with about 10–11% r.h. It is concludedthat while the seed viability constant C_w of the seed viabilityequation is species specific and therefore applies to most,if not all, cultivars of rice, variation in the value of K_Eis the source of the differences in potential longevity of thethree subspecies. Rice, Oryza sativa L, seed storage, seed longevity, seed moisture, viability equation     

The Role of Maturation Drying in the Transition from Seed Development to Germination: II. POST-GERMINATIVE ENZYME PRODUCTION AND SOLUBLE PROTEIN SYNTHETIC PATTERN CHANGES WITHIN THE ENDOSPERM OF Ricinus communis L. SEEDS

Kermode, A. R. and Bewley, J. D. 1985. The role of maturationdrying in the transition from seed development to germination.II. Post–germinative enzyme production and soluble proteinsynthetic pattern changes within the endosperm of Ricinus communisL. seeds.—J. exp. Bot. 36: 1916–1927. Immature seedsof Ricinus communis L. cv. Hale (castor bean) removed from thecapsule at 30 or 40 d after pollination (DAP) do not germinateunless first subjected to a desiccation treatment. This changefrom development to germination elicited by premature desiccationis also mirrored by a change, upon subsequent rehydration, inthe pattern of soluble protein synthesis within the endospermstorage tissue. Following rehydration of prematurely dried 30or 40 DAP seeds, soluble proteins characteristic of developmentcease to be synthesized after 5 h of imbibition, and those uniquelyassociated with germination and growth are then produced. Apattern of soluble storage protein breakdown comparable to thatfound in endosperms from mature seeds following imbibition isalso observed. In contrast, hydration of 40 DAP seeds immediatelyfollowing detachment from the mother plant results in a continuationof the developmental pattern of protein synthesis. Prematuredesiccation at 40 DAP elicits the production within the endospermof enzymes involved in protein reserve breakdown (leucyl ß–naphthylamidase;LeuNAase) and lipid utilization (isocitrate lyase; ICL) to levelscomparable to those observed in mature–hydrated endosperms.It is proposed that drying plays a role in redirecting metabolismfrom a developmental to a germinative mode; it also appearsto be a prerequisite for the induction of hydrolytic enzymesessential to the post–germinative (growth) phase of seedlingdevelopment. Key words: Desiccation-tolerance, germinability, seed development, castor bean     

Spatial and Developmental Variation in Seed Dormancy Characteristics in the Fire-responsive Species Anigozanthos manglesii(Haemodoraceae) from Western Australia

Anigozanthos manglesii(Haemodoraceae) is a colourful, herbaceousperennial exhibiting intra- and inter-populational variationin germination in response to smoke and heat. This study investigatedthe extent and nature of this variation in A. manglesii populationscollected along a 550 km latitudinal cline from kwongan scrub(30°S) to more mesic jarrah forest habitats (34°S) insouthwestern Australia. Variation in seed germination alonga maturing inflorescence was also investigated. Germinationof this species is known to be prolific following fire, andtwo germination treatments, aerosol smoke and heat, were usedas germination cues. There was a trend of increasing responsivenessof A. manglesii to smoke with increasing latitude along a clinalrange, but there were no differences in germination of seedsalong the cline in response to control or heat treatments. Therewas no significant difference in intra-population seed germinationin response to any treatment. Lastly, a significant and increasingresponse to smoke for seeds from the apex to base of the inflorescencewas detected. This latter trend may be attributed to higherresource allocation and an accelerated after-ripening of basipetalcompared to acropetal seeds. Possible reasons for the clinalvariation are discussed.Copyright 2001 Annals of Botany Company Anigozanthos manglesii, populations, geographical cline, inflorescence level, germination, smoke, heat, fire, seed development     

Accelerating Strawberry Seed Germination by Fungal Infection

Germination of strawberry seed was accelerated by natural andartificial infections of Ulocladium charatarum and other fungi,including the Arthrinium state of Apiospora montagnei and aCladosporium sp. Germination was variously promoted by fungiboth in light and darkness, on damp filter paper, water andmalt agar plates and on horticultural compost. Germinated seedlingswere apparently undamaged by these infections, although whencultured on malt agar the seedlings were overgrown by the fungus.Several other fungi promoted germination, but three of themlater killed the seedlings. Germination of seed of all threecultivars that were tested was promoted by fungal infectionwhich probably promoted germination by hastening breakdown ofthe seed coat. Strawberry, Fragaria ananassa Duch., germination, fungus     

The Influence of Genotype, Temperature and Moisture on Seed Longevity in Chickpea, Cowpea and Soya bean

Seed of three chickpea (Cicer arietinum L.), three cowpea [Vignaunguiculata (L.) Walp.] and four soya bean [Glycine max (L.)Merr.] cultivars were hermetically stored for up to 2 yearsin various constant environments which included temperaturesfrom —20 to 70 °C and moisture contents (fresh weightbasis) from 5 to 25 per cent. In all cases the survival curvescould be described by negative cumulative normal distributions.The longevity of the various seed lots differed but the valueof the standard deviation (the reciprocal of which gives theslope of the survival curve when percentage germination is transformedto probit) was the same for all cultivars within a species whenstored under similar conditions. Within each species the relativeeffects of moisture and temperature on longevity did not differsignificantly between cultivars. In all three species therewas a negative logarithmic relationship between seed moisturecontent and longevity, but the relative effect of moisture contentdiffered between the species: differences in the longevity ofsoya bean seed as a function of moisture content were less thanfor either cowpea or chickpea. The relative effect of temperatureon seed longevity did not differ between the three species,and the seed of all three species showed increasing temperaturecoefficients for the change in rate of loss of viability withincrease in temperature. The complete pattern of loss in viabilityin all three species can be described by a single equation whichwas developed for barley and has also been shown to apply toonion seed. The constants applicable to the three grain legumeshave been calculated so that it is now possible to predict percentageviability of any seed lot of these species after any storageperiod under a very wide range of storage conditions. Cicer arietinum L., chickpea, Glycine max (L.) Merr., soya bean, Vigna unguiculata (L.) Walp., cowpea, seed longevity, seed storage, moisture content, temperature     

Factors Influencing Seed Set in Triploid Musa spp. L. and Production of Euploid Hybrids

Seed set in triploid Musa spp. L. is very low due to high levelsof sterility. This makes cross breeding of plantain and bananadifficult. Nonetheless, several triploid plantain and bananacultivars produce seeds after hand pollination with diploidparents. This paper reports results about the pattern of seedvariation, success of in vitro germination and hybrid productionafter triploid-diploid crosses. Between-and within-clones differencesin seed set were observed. ABB cooking bananas had the highestrates of seed production followed by AAB French plantains. Plantainsproduced more diploid than tetraploid offsprings after triploid-diploidcrosses, which suggests that meiosis resulted in the productionof balanced haploid gametes (n = x) due to normal chromosomebehaviour between homologous genomes. Seed set variation withinclones was influenced by both the production of 2n (= 3x) gametesin the triploid parent and climatic factors. Indeed, seed production,embryo and seed germination success, and euploid and tetraploidhybrid production followed a pattern of seasonal variation reachinga peak in September. High frequency of seed with tetraploidembryos was obtained in the period from January to mid-March.The results demonstrate that production of desirable tetraploidswould be more efficient when hand pollinations are done underhigh temperature, high solar radiation and low relative humidity.These seem to be the most convenient conditions for relativelyhigh production of 2n eggs as compared to haploid gametes.Copyright1995, 1999 Academic Press Banana, fertility, embryo culture, Musa spp. AAA group, Musa spp. AAB group, Musa spp. ABB group, plantain, ploidy, seed set, 2n gametes     

Seed Coat Dormancy in Two Species of Grevillea(Proteaceae)

The role played by the seed coat in seed dormancy of Grevillealinearifolia(Cav.) Druce and G. wilsonii(A. Cunn.) was testedby a series of manipulations in which the seed coat was dissectedand removed, dissected and returned to the decoated seed, ordissected, removed and given a heat shock, and returned to thedecoated seed. Germination of intact seeds of both species wasalso examined after exposure to heat shock, smoke, or heat shockand smoke combined. Water permeability of the seed coat wasinvestigated by examining imbibition. For intact seeds, virtuallyno germination occurred under any treatment (G. wilsonii), orgermination was increased by exposure to either heat or smoke(G. linearifolia). Removal of the seed coat led to germinationof all decoated seeds for G. linearifolia, or a proportion ofdecoated seeds for G. wilsonii. Inclusion of smoked water inthe incubation medium led to a higher proportion of decoatedseeds germinating for G. wilsonii. Returning the seed coat,either with or without heat shock to the seed coat, did notsignificantly affect germination in either species. Seed coatswere permeable to water in both species. For the two Grevilleaspecies, there were different dormancy mechanisms that werecontrolled by the seed coat (G. linearifolia) or by both theseed coat and embryo (G. wilsonii). Copyright 2000 Annals ofBotany Company Grevillea linearifolia, Grevillea wilsonii, dormancy, seed coat dormancy, seed coat permeability, smoke, heat shock, germination     

The Influence of Seed Size Variation on Seed Germination and Seedling Vigour in Diploid and Tetraploid Dactylis glomerata L.

In this study the effects of seed size variation on germinationand seedling vigour have been investigated within and betweenploidy levels of diploid and related autotetraploid Dactylixglomerata. Rates of seed germination and seedling growth werecompared in two contrasting environments using diploid and tetraploidseeds of equal and also different biomass. Within each ploidylevel, seed biomass had no effect on either the overall percentagenor the rate of germination. In contrast, the comparison ofseeds of equal biomass but differing in ploidy level showedthat seeds from tetraploid plants germinated faster and to ahigher percentage than those from diploid plants. With respectto seedling growth, heavier seeds from the tetraploid genotypesgave seedlings of significantly higher biomass than those fromlighter tetraploid and diploid seeds throughout the 2 monthsof study. Interestingly, seeds of equal biomass but from differentploidy levels produced seedlings more similar than those fromthe extreme seed weight categories. These differences were maintainedin two different environmental conditions. These results suggestthat there is a complex interdependance of seed size and ploidyon seed germination and seedling growth but is not a simpleconsequence of differences in seed size between diploids andtheir related tetraploids.Copyright 1995, 1999 Academic Press Dactylis glomerata, polyploidy, seed size, germination, seedling     

Seeds latency of Stylosanthes hamata (Leguminosae) and its relation with morphology of the seed-coat]

The seed of Stylosanthes hamata is characterized by it's a high level of dormancy, which is imposed by seed-coat impermeability to water entry (harseededness or hard-seed condition). The level of hardseededness between upper and lower articulations of seven diploid and five tetraploid accessions was studied under tropical conditions. Germination tests on naked seeds (relative humidity: 55-65%, constant temperature: 27-30 degrees C, photoperiod: 12/12 hr) showed that hard-seed percentage was, in most cases, over 85% independent of ploidy level and seed position within the fruit. Histochemical analysis indicated that hardseededness in this species was associated with a completely sealed microphile and hilum. This feature was also associated to: a) an epidermis consisting of a palisade-like layer of macrosclereids, b) a like-line at the outermost region of these cells and c) a high concentration of hydrophobic compounds located all across the seed-coat.     

Potassium Release and Uptake in Germinating Legume Seeds in Relation to Seed Condition and Germination Environment

The levels of K^$ and total electrolyte leakage into leachingsolution from imbibed seeds of Pisum sativum L. and Phaseolusvulgaris L. have been followed to determine the relationshipof K^$ loss to the level of total electrolyte loss, and its relationto the physiological condition of the seed. The extent and rate of loss of both K^$ and total electrolytesvaried with both seed condition and the conditions imposed bythe experiment. K^$ accounted for between 25 and 50% of the totalelectrolyte leakage. The relationship was at all times significantlycorrelated, but changed with time and with experimental conditions. The effect of immersion, which increased electrolyte leakagedue to soaking injury, masked differences in seeds of varyingfield performance. Imbibition at either 5 °C or 40 °C before leaching wasshown to increase both K^$ and total electrolyte loss in comparisonto seeds imbibed at 25 °C. These results suggest that the ‘conductivity test’,which is used as a measure of seed deterioration, may need tobe re-examined in terms of experimental procedure and interpretation.     

Effect of Sporophytic Heterozygosity on the Male Gametophyte of the Tetraploid Potato (Solanum tuberosum L.)

Quantitative variation for pollen stainability was examinedin both tetraploid x diploid and tetraploid x tetraploid familiesof potato (Solanum tuberosum L.). The diploid parents, whichwere highly heterozygous, produced first division restitution(FDR) 2n pollen. The families used were not affected by cytoplasmic-geneticmale sterility. Significant differences between families werefound. FDR 2n pollen producing diploid clones had progenieswith a significantly higher pollen stainability than those derivedfrom crosses between tetraploid parents. This was related tothe level of heterozygosity in the sporophyte. In FDR 2n pollen,80% of the heterozygosity and a large fraction of epistasispresent in the diploid parent was transmitted to its tetraploidprogeny. This is important for the production of open pollinated,true potato seed, because pollen stainability is significantlycorrelated with fruit set (r = 0·85).Copyright 1994,1999 Academic Press FDR 2n pollen, gametophytic heterozygosity, true potato seed     

Control of Seed Growth in Soya Beans [Glycine max (L.) Merrill]

The seed is the primary sink for photosynthate during reproductivegrowth and an understanding of the mechanisms controlling therate of seed growth is necessary to understand completely theyield production process. The growth rate of individual seedsof seven soya bean [Glycine max (L.) Merrill] cultivars withgenetic differences in seed size varied from 10.8 to 3.9 mgseed^–1 day^–1. The growth rates were highly correlatedwith final seed size. The growth rate of cotyledons culturedin a complete nutrient medium was highly correlated with thegrowth rate of seeds developing on the plant and with finalseed size. The number of cells per seed in the cotyledons variedfrom 10.2 to 5.7 x 10⁶ across the seven cultivars. The numberof cells per seed in the cotyledons was significantly correlatedwith final seed size and the seed growth rate both on the plantand in the culture medium. The data suggest that genetic differencesin seed growth rates are controlled by the cotyledons and thenumber of cells in the cotyledons may be the mechanism of control. Glycine max L., soya bean, seed size, growth rate, cell number, sink activity     

The Effect of Temperature on Reproduction in FivePrimulaSpecies

Primula vulgarisHuds.,P. verisL.,P. frondosaJanka, and threepopulations ofP. farinosaL. were legitimately and illegitimatelypollinated, and the self-fertileP. scoticaselfed and cross-pollinatedand then subjected to uniform temperature conditions of 6, 15or 26 °C for 4 d before gynoecia were examined for pollengermination and pollen tube growth, or plants progressed toseed set at 15 °C, after which seeds were weighed, germinated,and seedlings grown on. The temperature responses of pollengermination and pollen tube growth were not always congruent,and varied between species, populations, and often between morphs(pin and thrum) in the distylous species. Nevertheless, optimaltemperature responses tended to be lower for vernal species(P. vulgarisandP. veris) and for subarcticP. scoticathan forlater flowering montane species. However, no relationship wasfound between pollen temperature response, and fertility. Thegreatest seed set occurred after legitimate pollination at 15°C in most cases; a flowering temperature of 26 °C tendedto impede seed set, except forP. scoticaand the low altitudepopulation ofP. farinosa. InP. veris, P. frondosaand the highaltitude population ofP. farinosa,some illegitimate pollen germinationand pollen tube growth occurred at 26 °C, but this did notlead to increased within-morph seed set in these self-incompatiblespecies at this relatively high temperature. Temperature atflowering frequently affected average seed weight, and inP.verisand two populations ofP. farinosathis attribute may havebeen influenced by seed number, the average seed weight of few-seededcapsules tending to be greater than for many-seeded capsules.A high seed weight might mitigate the disadvantageous effectsof low fecundity resulting from interactions with floweringtemperature. However, inP. vulgarisandP. scoticainteractionsbetween flowering temperature and seed weight may have other,undetermined, causes. The seed of four species germinated leastwell in standard conditions when set following a flowering temperatureof 6 °C, which tends to support the hypothesis that temperatureat flowering can affect seed physiology; in contrast the seedof the two upland populations ofP. farinosagerminated leastwell after flowering at 26 °C. We conclude that much morework is needed on interactions between temperature and reproductiveefficiency, but that preliminary indications suggest that aglobal increase in temperature at flowering might adverselyaffect the quantity and quality of seed set in some species.Copyright1998 Annals of Botany Company Distyly, pollen tube,Primula farinosa, Primula frondosa, Primula scotica, Primula veris, Primula vulgaris,reproduction, seed set, temperature.