The Effects of Kinetin and Gibberellin on the Germination of Dehusked Seeds of Indica and Japonica Rice (Oryza sativaL.) under Anaerobic and Aerobic Conditions

The effects of kinetin and gibberellin were examined under anaerobicconditions (0% oxygen) and aerobic conditions (20% oxygen) onthe germination of dehusked seeds of indica and japonica ricecultivars that had been harvested at different times duringthe formation of seeds. Surjamkhi was used as a representativeof deep dormant indica cultivars and Assam IV as a less dormantindica cultivar. Sasanishiki was used as the japonica rice cultivar.Both phytohormones were applied at a concentration of 10^-3Mwhichproved to have the greatest stimulatory effect in preliminarywork at concentrations of 10^-3–10^-5M. Under aerobic conditions,inhibition of germination by dehusking of Sasanishiki seedsthat had been harvested either 30 or 60 d after anthesis wasovercome by kinetin and all seeds germinated. Complete germinationinduced by kinetin under aerobic conditions was also achievedwith the dehusked seeds of the indica rice cultivar Assam IVthat had been harvested on two occasions and of Surjamkhi thathad been harvested 28 d after anthesis. In contrast, germinationof dehusked japonica seeds stimulated by anaerobiosis was inhibitedby kinetin. The stimulatory effects of gibberellin on the germinationof indica and japonica rice seeds were observed under aerobicand anaerobic conditions. Under anaerobic conditions, the responsesof dehusked indica and japonica rice seeds to kinetin and gibberellindiffered, being negative with kinetin and positive with gibberellin.Under aerobic conditions, the stimulatory effects of kinetinon germination of dehusked seeds were greater than those ofgibberellin. Thus, treatment with kinetin appears to be usefulfor breaking the considerable dormancy commonly observed inthe dehusked seeds of indica rice. Mechanisms are proposed toexplain the stimulatory effects of these phytohormones on thegermination of dehusked seeds of indica and japonica rice underaerobic and anaerobic conditions. Rice; Oryza sativaL.; seed germination; dehusking treatment; gibberellin; indica; japonica; kinetin; oxygen; dormancy; germination inhibition; seed formation     

Removal of the pericarp and testa of seeds of japonica and indica rice (Oryza sativa) at various oxygen concentrations has opposite effects on germination

The germination of intact, dehusked, and peeled seeds (caryopses) of the japonica rice cultivar Sasanishiki, harvested 30, 40, 47 and 60 days after anthesis, and of the indica rice cultivar Assam IV, harvested 14 and 28 days after anthesis, was examined. Dehusking strongly inhibited germination of Sasanishiki seeds, with the exception that seeds harvested 30 days after anthesis gave minimal germination percentages even when left intact. Peeling (removal of the pericarp and testa) restored or enhanced germination, and 60–100% of seeds germinated after 10 days. By contrast, the rank order of germination of Assam IV seeds was intact, dehusked, and peeled seeds, with peeled seeds yielding germination percentages of 100%. In Sasanishiki, inhibition of germination of peeled seeds was observed at reduced oxygen concentrations (1–4% oxygen). This inhibition might explain the inhibitory effects of dehusking on germination of seeds from the japonica cultivar. It is possible that the testa and pericarp, which cover the embryos of dehusked seeds, acted as a barrier to the diffusion of oxygen to the embryo.     

Differences in the Effects of Dehusking during Formation of Seeds on the Germination of Seeds of Indica and Japonica Rice (Oryza sativaL.)

Differences in germination of intact and dehusked seeds of two japonica and two indica cultivars of rice (Oryza sativaL.) were examined during the development and maturation of seeds both under high-temperature (30/23°C) and low-temperature (20/13°C) regimes and a 14-h photoperiod in growth cabinets. As described previously for seeds grown in the paddy fields, germination of freshly harvested japonica rice seeds that developed and matured in growth cabinets was inhibited by dehusking. We observed a roughly consistent triphasic pattern with respect to the germination of intact and dehusked seeds during the development and maturation of seeds of indica and japonica rice. The triphasic pattern consisted of: (a) an initial phase, during which germination was stimulated by dehusking both in indica and japonica rice; (b) a second phase during which almost no dehusked seeds of indica or japonica rice germinated; and (c) a third phase during which intrinsic differences between indica and japonica rice were observed, with dehusking stimulating germination of indica rice but inhibiting that of japonica. Temperature regimes did not affect this triphasic pattern, but the time from the day of anthesis to mass maturity was affected by temperature regimes, and the effect was more pronounced in indica than in japonica rice.     

Germination and Dormancy in Immature and Fresh-mature Lettuce Seeds

The effects of red light, far-red light, Gibberellin A₃, andethephon were studied on the germination of lettuce seeds cv.Grand Rapids harvested at different stages of development. Seeds did not become capable of germination until 8 days afteranthesis. Red light promoted seed germination from the age of8–9 days following anthesis up to the newly mature stage.Ten or 11 days following anthesis, a large percentage of seedsbecame capable of germination in the dark and therefore couldbe considered not dormant. They were affected by far-red light,but less so than the mature seeds. The effect of light on the germination of developing seeds appearedto be similar to the known light effect on mature lettuce seedgermination. Gibberellin A₃ and ethephon had no effect on immatureand fresh seed germination. Lactuca sativa L., Lettuce, germination, dormancy, red light, far-red light, gibberellin A₃, ethephon     

Patterns of seed after-ripening in Bromus tectorum L

For grass seeds that lose dormancy through after ripening indry storage, the probability of germination following a particularwetting event can be predicted only if the relationship betweenstorage temperature and change in after-ripening status is known.This study examined patterns of seed dormancy loss in Bromustectorum L., quantifying changes in germination percentage,speed, and uniformity through time. Seed collections from threesemi-arid habitats were stored at temperatures from 10–40C. At monthly intervals, subsamples were incubated at 5/15,10/20, 15/25, and 20/30 C. For recently harvested seeds, germinationpercentage, mean germination time, and days between 10% and90% of total germination (D90–D10) ranged from 1–75%,10–24 d, and 10–20 d, respectively. Recently harvestedseeds were generally most dormant, slowest to germinate andleast uniform at high incubation temperatures. In contrast,after ripened seeds for all collections had nearly 100% germination,mean germination times <5 d, and D90–D10 values <5d. Three indices were used to characterize after-ripening ratesfor each seedlot at each incubation temperature. The mean dormancyperiod, the mean rate index, and the mean uniformity index definedthe storage period required for seedlots to become half as dormantas at harvest, to progress half-way to the fastest speed, andto progress half-way to the greatest uniformity, respectively.Seeds required longer storage to germinate uniformly than togerminate completely or quickly, because germination time-coursecurves for incompletely after-ripened seeds were positivelyskewed rather than sigmoidal. Mathematically, the three indiceswere described as negative exponential functions of storagetemperature, which suggests that after-ripening is likely completedin late summer or early autumn regardless of summer conditions. Key words: Seed dormancy, germination timing     

Responses of Vegetable Seeds to Controlled Hydration

Leek, onion and carrot seeds were imbibed in water and in solutionsof polyethylene glycol (PEG) 6000 over the range –0.5to –4.0 MPa osmotic potential, for periods up to 28 dat 15 C. Seeds started to germinate after 7 and 14 d at –0.5MPa and –1.0 MPa PEG, respectively, but in the lattercase, germination did not exceed 5%. No germination occurredin solutions of lower (more negative) osmotic potential. Seedmoisture content increased with osmotic potential in all threespecies and the relationships were unaffected by the durationof imbibition in solutions of –1.0 to –4.0 MPa,though leek seeds had higher moisture contents than the otherspecies for any given osmotic potential. Linear relationships between response to priming (differencebetween mean germination times of primed and untreated seeds)and seed moisture content were obtained for each species, positiveresponses being obtained above 30–35% seed moisture contentwith optima at 46, 44.5 and 44% seed moisture contents in leek,onion and carrot, respectively. Priming had no effect on embryovolume or cell number per embryo in leek and onion. Carrot embryovolume increased by 43% and cell number per embryo doubled inprimed compared with untreated seeds, whereas seeds imbibedin water showed only a slight increase in cell number per embryoat the stage when radicles were beginning to penetrate the seedcoat. Allium cepa L. cv. Rijnsburger Robusta, onion, Allium porrum L. cv. Winterreuzen, leek, Daucus carota L. cv. Nantaise, carrot, germination, priming, polyethylene glycol, seed moisture, cell number, embryo volume     

The effect of temperature and CO2 on seed quality development in wheat (Triticum aestivum L.)

Winter wheat (Triticum aestivum L.) cv. Hereward was grown inthe field in two double-walled polyethylene-covered tunnelswithin each of which a temperature gradient was superimposedon diurnal and seasonal fluctuations in temperature. The meantemperature between anthesis and harvest maturity varied from14.3 to 18.4C among plots within these tunnels. The CO₂ concentrationwas controlled at different values in each tunnel; seasonalmean concentrations were 380 and 684 µmol CO₂ mol^–1air. Crops were also grown outside the tunnels at ambient temperaturesand CO₂. Samples of seeds were harvested sequentially from eachplot between anthesis and harvest maturity. Seed germinationand seed survival during subsequent air-dry storage were determinedfor each sample. The onset of both ability to germinate anddesiccation tolerance (ability to germinate after rapid desiccationto 10–15% moisture content and subsequent rehydration)coincided in all environments. Full germination capacity (>97%, determined at 10C) was reached 4–18 d before theend of the seed-filling phase (mass maturity) in most cases.There was little or no decline in germination capacity duringsubsequent seed development and maturation. Differences in seedquality were evident, however, throughout seed development andmaturation when seed survival curves during subsequent storagewere compared. Potential longevity in air-dry storage (assessedby the value K₁ of the seed viability equation) improved consistentlyboth before and after mass maturity. There was a significantpositive relation between the rate of increase in potentiallongevity (dK₁Idt) and temperature (the minimum temperaturefor seed quality development was 4.8 C), but neither CO₂ concentrationnor production within the polyethylene tunnels affected thisrelation. Key words: Wheat, Triticum aestivum L., seed development, seed longevity, carbon dioxide, temperature     

Water Relations of Seed Development and Germination in Muskmelon (Cucumis melo L.): VII. INFLUENCE OF AFTER-RIPENING AND AGEING ON GERMINATION RESPONSES TO TEMPERATURE AND WATER POTENTIAL

The effects of storage conditions on the germination of developingmuskmelon (Cucumis melo L.) seeds were tested to determine whetherafter-ripening is required to obtain maximum seed vigour. Seedswere harvested at 5 d intervals from 35 (immature) to 60 (fullymature) days after anthesis (DAA), washed, dried, and storedat water contents of 3·3 to 19% (dry weight basis) at6, 20, or 30°C for up to one year. Germination was testedin water and in polyethylene glycol 8000 solutions ( –0·2to –1·2 MPa osmotic potential) at 15, 20, 25 or30°C. Germination percentages and rates (inverse of meantimes to radicle emergence) were compared to those of newlyharvested, washed and dried seeds. For 40 and 60 DAA seeds,one year of storage at 20°C and water contents <6·5%significantly increased germination percentages and rates at20°C, but had little effect on germination at 25 and 30°C.Storage reduced the estimated base temperature (T_b) and meanbase water potential (_b) for germination of both 40 and 60 DAAseeds by approximately 5°C and 0·3 MPa, respectively.Immature 35 DAA seeds showed the greatest benefit from storageat 3 to 5% water content and 30°C, as germination percentagesand rates increased at all water potentials (). Storage underthese same conditions had little effect on the germination ofmature seeds in water, but increased germination percentagesand rates at reduced 's. Accelerated ageing for one month at30°C and water contents from 15 to 19° increased germinationrates and percentages of mature seeds at reduced 's, but longerdurations resulted in sharp declines in both parameters. Immatureseeds lost viability within one month under accelerated ageingconditions. An after-ripening period is required at all stagesof muskmelon seed development to expand the temperature andwater potential ranges allowing germination and to achieve maximumgerminability and vigour. Post-harvest dormancy is deepest atthe point of maximum seed dry weight accumulation and declinesthereafter, both in situ within the ripening fruit and duringdry storage. Key words: Muskmelon, Cucumis melo L., seed, development, dormancy, germination, vigour, after-ripening     

Temperature Dependence of Viability and Dormancy of Zizania palustris var. interior Seeds Stored at High Moisture Contents

Seeds (caryopses) of North American wild rice (Zizania palustrisvar. interior), a temperate aquatic grass, have been thoughtto require storage at low temperatures and high moisture contentsto preserve viability. The seeds are also deeply dormant atmaturity and require up to 6 months of stratification to breakdormancy. We report here that wild rice seeds can retain viabilityat moisture contents 30% (f. wt. basis) for up to 6 monthsat temperatures as high as 30 °C, and for at least 1 yearat temperatures below 20 °C. Dormancy is not broken at temperaturesabove 10 °C, but subsequent stratification requirementsare unaffected by prior warm storage. Cold storage is thereforenot required to maintain viability of wild rice seeds, but isnecessary to break dormancy. Hydrated wild rice seeds can befrozen to –10 °C without damage, but dormancy is notlost at subfreezing temperatures. These results provide newoptions for long-term storage of wild rice seeds. Zizania palustris var. interior (Fassett) Dore, wild rice, seed, germination, dormancy, storage, moisture content     

Dormancy in Rice Seed: III. THE INFLUENCE OF TEMPERATURE, MOISTURE, AND GASEOUS ENVIRONMENT

The influence of storage conditions—temperature, moisturecontent, oxygen, nitrogen, and carbon dioxide—on dormancyin rice seed has been investigated. The effects of temperatureand oxygen when the seeds have been set to germinate have alsobeen studied. Storage in oxygen accelerates the breaking of dormancy; at lowertemperatures, the effect of oxygen is more noticeable. Carbondioxide and nitrogen have little or no effect except in so faras they exclude oxygen. It is shown that there is a negativelinear relationship between storage temperature and log. meandormancy period of intact seeds over the range 27°C. to47°C. In the variety tested, the Q₁₀ for the rate of breakingdormancy is 3.38. Variation of moisture content over the range12.0–14.5 per cent, has little effect at 27°C. andno detectable effect at higher temperatures. When dormant seeds are soaked in water, they attain a moisturecontent close to 30 per cent. Pre-soaking seeds to achieve moisturecontents in this region can stimulate the breaking of dormancywhen compared with dry storage. At laboratory temperature (meanabout 27°C.) the stimulation caused by pre-soaking intactseeds is usually small and sometimes non-existent, but at alow temperature (3°C.) the stimulation is increased; butdry storage at 3°C. markedly delays the breaking of dormancy.When seeds are dehusked, a large proportion lose their dormancy.Much of the residual dormancy of dehusked seeds can be brokenby soaking at laboratory temperature. But in the sample of dehuskedseeds used, low temperature did not increase the effect of thepre-soaking, but slightly decreased the stimulation caused bythe soaking treatment in this case. The effect of temperature on wet seed has also been investigatedwhen the seed has been set to germinate. Maximum germinationof a partially dormant population of seed is achieved at anoptimum temperature which is near or somewhat below 27°C.In the sample tested, no germination occurred at 42°C.,although in populations which have completely broken dormancyfull germination will occur at this temperature. Non-dormantpopulations of rice seed can germinate at very low oxygen tensionsor probably even in the absence of oxygen, but germination ofa partially dormant sample is reduced under these circumstances.When oxygen tension is very low there is less germination at27°C. than at 37°C. In some varieties, at least, there is evidence that the seedsgo through a stage when they will germinate in daylight butnot in the dark. A simple practical method for rapidly breakingthe dormancy of intact seeds is described. The significanceof these results is discussed in relation to the published workon seeds of other species.     

Freezing injury to ovules, pollen and seeds in winter rape

Winter rapeseed (Brassica napus, cv. Samouraï) flowersearly in spring and, under field conditions, short freezingperiods can occur. Unacclimatized plants were freeze-stressed(–3°C for 4 h) at different developmental stages ofbuds, open flowers and seeds. The dissection of pistils from stressed plants showed that freezingresults in shrivelled ovules. We assessed freezing injury onthe basis of per cent of shrivelled ovules: ovule sensitivitybegins early (8 d before anthesis) but increases up to anthesis.Crosspollination of stressed pistils with non-stressed pollenshowed that recording of freeze-injured ovules is a good methodfor early estimation of the effect of stress on seed yields. On the other hand, stress does not reduce the viability of pollen,except when it was applied at the binucleate pollen stage. Useof frozen pollen x nonstressed pistils has little effect onseed yields. Freeze injury on seeds was assessed by seed filling:seeds are very susceptible just after fertilization until 20d after fertilization (DAF). Freezing seems to inhibit seedfilling. A germination test of stressed seeds during their developmentindicated that embryo viability is not affected if the stressoccurs after 35 DAF. As the embryos develop, resistance to stressincreases. Key words: Brassica napus, rapeseed, freeze injury, pollen and ovule, seed filling     

Seed Longevity of Rice Cultivars and Strategies for their Conservation in Genebanks

Changes in seed quality during ripening were studied in sixteencultivars of rice, representing the three ecogeographic racesofOryza sativa, and one cultivar ofO. glaberrima, grown duringone dry season (Nov. –May) 1992 –1993 at Los Baños, Philippines. Mass maturity (defined as the end ofseed filling period) among the cultivars was attained between18.5 and 21.6d after anthesis (DAA). The seed moisture contentat mass maturity varied between 24 and 40%. Germination abilityof seeds in the early stages of development varied significantly,but as mass maturity approached, germination increased to themaximum and no significant differences were found among cultivars.The seeds were stored hermetically at 35 °C with 15±0.2%moisture content and the resultant seed survival data were analysedby probit analysis. Potential longevity (quantified by the valueof seed lot constantK_iof the seed viability equation) was greatestbetween 33 and 37 DAA, i.e. about 2 weeks after mass maturity.The stage during development at which seeds achieve maximumpotential longevity is described by the term storage maturity.Lowlandjaponicacultivars, large seeded accessions (seed mass40mg) andO. glaberrimahad shorter storage longevity ( , standarddeviation of the frequency of seed deaths in time=1.47 weeks)while cultivars with purple pericarp survived longer than othercultivars ( =2.33 weeks). The initial germination of thejaponicacultivarsat storage maturity was high (99 –100%) and the estimatesof maximum potential longevity (K_i) which ranged between 3.3(Shuang cheng nuo) and 4.4 (Minehikare) were close to thoseof theindicacultivars. This research suggests that seed production environment betweenNov. and May at Los Ba ños is benign for the temperatejaponicacultivars.The implications of these results on management of rice geneticresources are discussed. Oryza sativaL.; rice; germplasm conservation; seed production environment; seed development; seed longevity     

Desiccation Intolerance in Seeds of Zizania palustris is Not Related to Developmental Age or the Duration of Post-harvest Storage

Freshly harvested seeds of Zizania palustris L. representingfour distinct stages of development were intolerant of desiccation.Rapid drying did not improve survival. The relationship betweenprobit viability and embryo moisture content for freshly harvestedmature seeds was identical to that described in an earlier publicationfor seeds previously stored fully imbibed at low temperaturesto remove dormancy. A small reduction in embryo moisture contentduring the first 3 d of drying at 15% r.h. and 15°C ledto a highly sigificant (P < 0.01) increase in the proportionof fresh seeds capable of germination in response to a rangeof dormancy breaking factors including giberellins. Resultsare discussed in relation to previous work on recalcitrant seedsand to the widely reported developmental changes in orthodoxseeds which are triggered by desiccation. Zizania palustris, wild rice, seeds, drying, desiccation intolerance, development     

Water Relations of Seed Development and Germination in Muskmelon (Cucumis melo L.): VIII. DEVELOPMENT OF OSMOTICALLY DISTENDED SEEDS

Dead seeds that expand to nearly twice their normal volume whenfully hydrated are called osmotically distended (OD). Theseseeds swell osmotically in response to a water potential ()gradient created by solutes trapped in the free space betweenthe embryo and the surrounding endosperm or perisperm tissues.The formation of OD seeds in planta is poorly understood, althoughthey often occur in newly harvested muskmelon (Cucumis meloL. Reticulatus group) seed lots. Muskmelon fruit senescenceand seed germinability were contrasted with Armenian cucumber(Cucumis melo L. Flexuosus group) from 50 d after anthesis (DAA)to when seeds were released from the fruit. Fifty DAA muskmelonseeds were incubated in the laboratory for 30 d at 15, 25, and35 °C in factorial combinations of ethanol, acetic acid,and to simulate conditions in decaying fruits. Seed releasefrom Armenian cucumber occurred 20 d earlier than muskmelon.In both years of the study, less than 25% of the muskmelon seedsreleased from the fruit were viable, and 52% and 24% of thedead seeds were OD in year one and two, respectively. All Armeniancucumber seeds were viable or had germinated precociously atseed release. From 50 to 60 DAA, soluble solids in muskmelonfruit pericarp tissue declined from 11·4 to 7·8° Brix, pH declined from 6·2 to 5·1, increasedfrom –1·76 to –1·36 MPa, acetic acidincreased to 61 mol m^–3;, and ethanol content rose from0·1% to 0·3%. O₂ and CO₂ partial pressures inthe seed cavities of 40 to 55 DAA fruits were generally 12 and8 kPa, respectively, at midday. All 50 DAA muskmelon seeds incubatedin acetic acid and ethanol germinated, because these chemicalscould not penetrate the perisperm tissue. Incubating 50 DAAmuskmelon seeds in the laboratory for 30 d at 15 or 25 °Chad little effect on germinability, regardless of . Germinationpercentages of muskmelon seeds incubated at 35 °C and 's<–1·28MPa were less than 50%. Muskmelon seeds died and became OD insidedecaying fruits in the field because of the combined effectsof low , high temperature, and low O₂ partial pressures. Fruitsof muskmelon cultivars bred to resist decomposition and to havehigh sugar content showed decreased reproductive capacity comparedto Armenian cucumber which decomposed more rapidly. Key words: Muskmelon, seed, fruit, germination, senescence, water potential, temperature, oxygen, carbon dioxide     

Water Status Changes During Development in Relation to the Germination and Desiccation Tolerance of Aesculus hippocastanum L. Seeds

Seed growth characteristics of Aesculus hippocastanum were examinedin detail during development from about 70 to 140 d after anthesis(DAA), mainly in 1988 and 1989. Mean fresh and dry weights increasedfor both the axis and the whole seed up to the time of peakseed fall at 135 DAA with no cessation before fruit abscission.Water per seed increased up to 100 DAA, after which no furtherincrease occurred; moisture content declined for the embryonicaxis and whole seed respectively from above 75 and 65% at 95DAA to 65 and 50% at 130 DAA. At fruit shedding in 1990 waterpotential values of -1·2, -2·6 and -1·1MPa were observed for the testa, cotyledon and axis tissuesrespectively; relevant sorption isotherms are presented. Decreases in seed moisture content during development were accompaniedby increases in desiccation tolerance and in germinability,both reaching their maximum at the time of peak seed fall. Atmaturity, only about 10% viability was retained on drying seedto 20% moisture content; it is confirmed that the seeds are'recalcitrant'. The exact relationship between moisture contentand germination during development was dependent on the deptof dormancy, as judged by the period of chilling required; eachduration of chilling at 2°C within the range 3-12 weeksyields a curve of sigmoid shape. No germination occurred at26°C without chilling, but nearly full germination can beobserved for samples collected at 6 weeks before maximum seedfall with 12 weeks chilling. The rate of moisture loss duringdesiccation at 15°C and 15% rh becomes reduced during development.The ontogeny of these 'recalcitrant' seeds is compared withthat of 'orthodox' seeded species and the implication of sigmoid-shapedcurves for the relationship between seed moisture content andgermination are considered.Copyright 1993, 1999 Academic Press Aesculus hippocastanum L., horse chestnut, seed development, water status, germination, desiccation intolerance, desiccation rate     

Protein Synthesis During Rehydration, Germination and Seedling Growth of Naturally and Precociously Matured Soybean Seeds (Glycine max)

Soybean seeds [Glycine max (L.) Merr.] synthesize de novo andaccumulate several non-storage, soluble polypeptides duringnatural and precocious seed maturation. These polypeptides havepreviously been coined ‘maturation polypeptides’.The objective of this study was to determine the fate of maturationpolypeptides in naturally and precociously matured soybean seedsduring rehydration, germination, and seedling growth. Developingsoybean seeds harvested 35 d after flowering (mid-development)were precociously matured through controlled dehydration, whereasnaturally matured soybean seeds were harvested directly fromthe plant. Seeds were rehydrated with water for various timesbetween 5 and 120 h. Total soluble proteins and proteins radio-labelledin vivo were extracted from the cotyledons and embryonic axesof precociously and naturally matured and rehydrated seed tissuesand analyzed by one-dimensional PAGE and fluorography. The resultsindicated that three of the maturation polypeptides (21, 31and 128 kDa) that had accumulated in the maturing seeds (maturationpolypeptides) continued to be synthesized during early stagesof seed rehydration and germination (5–30 h after imbibition).However, the progression from seed germination into seedlinggrowth (between 30 and 72 h after imbibition) was marked bythe cessation of synthesis of the maturation polypeptides followedby the hydrolysis of storage polypeptides that had been synthesizedand accumulated during seed development. This implied a drasticredirection in seed metabolism for the precociously maturedseeds as these seeds, if not matured early, would have continuedto synthesize storage protein reserves. Glycine max (L.) Merr, soybean, cotyledons, maturation, germination/seedling growth     

The Effects of Priming and Ageing on Seed Vigour in Tomato

A comparison was made of the effects of seed priming or ageingtreatments on the performance of tomato (Lycopersicon esculentumMill. cv. UC204C) seeds according to a number of indices ofseed vigour. A single lot of tomato seeds was primed in 120mol m^–3 K2HPO4 + 150 mol m^–3 KNO₃ for 5 d at 20?C, or aged at 13% moisture content (dry weight basis) and 50?C for 6 d. Germination percentage (>98%) was unaffectedby priming and reduced to 85% by ageing. X-ray photographs andlongitudinal sections revealed the formation of free space surroundingthe embryo in dry primed seeds, which was not evident in controlor aged seeds. Priming increased the rate of germination atall temperatures above the base temperature (T_b), while ageingdecreased it. T_b was unaffected by priming and only slightlyincreased by ageing. The variation in individual times to germinationwas approximately doubled in both primed and aged seed comparedto the control, based upon the slopes of probit germinationpercentage versus log thermal time curves. Root growth aftergermination tests and seedling growth in both greenhouse andfield tests were not influenced by either priming or ageing.The conductivity test was found to be unreliable as a vigourtest for tomato seeds. The results identify several indiceswhich can be used to quantify seed vigour in tomato. They alsoillustrate that seed priming can enhance seed performance accordingto some criteria, while having no effect or decreasing qualityaccording to other criteria. Seed vigour can apparently be separatedinto various components which can be independently influencedby seed enhancement treatments. Key words: Tomato, seed germination rate, seed priming, seed vigour     

The Role of ABA in the Control of Apple Seed Dormancy Re-appraised by Combined Gas Chromatography-Mass Spectrometry

Measured by GC—MS²—SIR³, endogenous ABA⁴ in embryonicaxes of seeds of Malus pumila L. cv. Golden Delicious decreased8-fold and cotyledon ABA by only 60%, during 10–50 d ofstratification at 5 ?C, after ABA leaching during an initial24 h soaking. During stratification, the percentage germinationof embryos transferred to 17?C showed a significant linear dependenceon log_e of ABA levels in the axes at transfer. Between 50 and70 d, ABA levels increased markedly in axes and testa both ofstratified seeds and seeds allowed to re-dry at 17 ?C afterinitial soaking. The ability of fully stratified axes with elevatedendogenous ABA to germinate indicated that stratification haddecreased their ABA sensitivity. Changes in cotyledon ABA couldnot account for the promotory effect of cotyledons on germinationduring the first 30 d of stratification. Loss of testa inhibitionof germination during stratification was not linked with changesin testa ABA. Stratification markedly increased the sequestrationin the axes of exogenous ABA supplied via the cotyledons. Changesboth in axis ABA levels and sensitivity were thus correlatedwith dormancy release, but subject to modifying control by thecotyledons and testa not involving ABA. Rehydration of driedseeds affected axis ABA later during storage via mechanismsunconnected with dormancy. Key words: ABA, seed dormancy, stratification     

Water as a Storage Medium for Elaeis guineensis (pisifera) Seeds under Aseptic Conditions

Over 50 per cent germination has been obtained from Elaeis guineensisform pisifera seeds stored in unaerated sterile distilled waterfor 6 months. The moisture levels of the seeds and excised embryoswere of the same order (20–30 and 60–70 per cent,respectively) as those of fully imbibed fresh seeds. The implicationsof an apparent lower oxygen requirement by seeds stored underwater as against germinating seeds are discussed in the contextof the successful storage. Elaeis guineensis, pisifera, germination, seed dormancy, embryo     

Moisture Content and the Longevity of Seeds of Phaseolus vulgaris

The lower limit to the negative logarithmic relation betweenseed longevity and moisture was determined in bean (Phaseolusvulgaris L.). Sub-lots of seed were hermetically stored at 65°C and 11 moisture contents (3.26–13.6% f. wt) forup to 80 d, tested for germination and the seedlings evaluated.In accordance with the seed viability equation, there was anegative logarithmic relation between moisture content (%, f.wt) and longevity. Two different criteria for estimating theslope constant of this relation gave similar values of 4.76(s.e. 0.26) and 4.82 (s.e. 0.24). The calculated lower moisturecontent limits to the relation were 5.7 and 5.6%, respectively,values at equilibrium with 10.6–10.8% relative humidity(rh). Further drying to 3.26% had little additional effect onlongevity, but initial germination was slightly reduced. Theresults are discussed in relation to water potential and comparedwith other crops. Arguments against transforming germinationvalues to disregard the seeds initially failing to germinateare emphasized. Common bean, Phaseolus vulgaris L. cv. Provider, seed storage, seed longevity, seed moisture, viability equation, water relations