'Callose' in the Impermeable Seed Coat of Sesbania punicea

Dry legumes of Sesbania punicea (Cav.) Benth. contain impermeableseeds which are either beige-greenish or reddish. When keptin water for over one year they do not swell. Quick imbibitionwas induced by a deep cut, abrasion with coarse abrasive paper,immersion in concentrated sulphuric acid, in boiling water andin boiling KOH solutions. Neither lipid solvents (acetone, chloroform,cyclohexane, diethyl ether, ethanol, xylene), nor, at room temperature,KOH solutions up to 50% per cent, permeabilized the seeds. Astrong barrier to water entry appeared to be located in thepalisade layer which showed ‘light points’ in places,and which seemed to be transversal thickenings. In the testa,‘ callose’, which may play a role in the impermeabilityof the Sesbania punicea seed, was detected. Sesbania punicea, germination, seed dormancy, seed coat impermeability, ‘callose’     

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     

Testa is involved in the control of storage mobilisation in seeds of <Emphasis Type="Italic">Sesbania virgata</Emphasis> (Cav.) Pers., a tropical legume tree from of the Atlantic Forest

Seeds of Sesbania virgata (Cav.) Pers. (Leguminosae) contain galactomannan as a cell wall storage polysaccharide in the endosperm. After germination, it is hydrolysed by three enzymes: α-galactosidase (EC 3.2.1.22), endo-β-mannanase (EC 3.2.1.78) and β-mannosidase (EC 3.2.1.25). This work aimed at studying the role of the testa (seed coat) on galactomannan degradation during and after germination. Seeds were imbibed in water, with and without the testa, and used to evaluate the effect of this tissue on storage mobilisation, as well as its possible role in the galactomannan hydrolases activities. Immunocytochemistry and immunodotblots were used to follow biochemical events by detecting and localising endo-β-mannanase in different tissues of the seed. Endo-β-mannanase and α-galactosidase activities were found in the testa and latter in the endosperm during galactomannan degradation. The former enzyme was immunologically detected in the testa, mainly during germination. The absence of the testa during imbibition led to the anticipation of protein mobilisation and increased of the α-galactosidase activity and galactomannan degradation. Thus, the testa appears to play a role during storage mobilisation in the legume seed of S. virgata probably by participating in the control of the production, modification and/or storage of the hydrolases.     

Changes in Seed Constituents During Germination and Seedling Growth of Precociously Matured Soybean Seeds(Glycine max)

During 7 d of precocious maturation of soybean seed (Glycinemax), the starch content declined and soluble sugar levels increasedin patterns similar to natural seed dehydration and maturation.Total seed protein content and total seed dry weight increasedwhereas oil content remained relatively unchanged. Overall,the proportions of the constituents in precociously maturedseeds were comparable to naturally mature seeds. Precociouslymatured soybean seeds showed much the same germination and seedlinggrowth frequency patterns as naturally matured seeds. Duringgermination and seedling growth of precociously matured seeds,starch, soluble sugar, protein and oil levels followed patternssimilar to naturally mature, germinating seeds and seedlings.Therefore, precocious maturation may be used as a model systemto investigate the control of the physiological and biochemicalevents occurring during seed maturation which lead to germinationand subsequently, seedling growth. Glycine max (L.) Merr., soybean, cotyledons, maturation, germination/seedling growth     

Water Relations of Seed Development and Germination in Muskmelon (Cucumis melo L.): II. DEVELOPMENT OF GERMINABILITY, VIGOUR, AND DESICCATION TOLERANCE

The germinability, vigour, and desiccation tolerance of muskmelon(Cucumis melo L. cv. Top Mark) seeds was studied in relationto changes in seed water content during development within thefleshy fruit. Seed water content (fresh weight basis) declinedfrom 91% to 42% between 10 d and 35 d after anthesis (DAA) (whenmaximum dry weight was attained), then declined more slowlyto a minimum of 35% at 50 DAA before increasing again to 43%at 65 DAA. Fresh intact seeds were first germinable at 25 to30 DAA and attained maximum germination percentages at 45 DAA.Between 15 and 35 DAA, cotyledons, hypocotyls, radicles andepicotyls of isolated embryos (testa and perisperm enveloperemoved) sequentially developed the ability to grow when incubatedon water. Dehydration to water contents less that those attainedwithin the fleshy fruit is not a requirement for developmentof germination capacity of muskmelon seeds. Seeds became tolerantof rapid desiccation after 25 DAA, and drying of immature seeds(25 to 40 DAA) increased their germination percentages uponsubsequent imbibition. Washing, drying, or washing followedby drying increased seedling vigour (root length) as comparedto fresh seeds, which had very poor vigour. Water absorptionisotherms were constructed to test whether changes in water-bindingcomponents were correlated with the development of desiccationtolerance. Isotherms for seeds older than 25 DAA fit well tothe D'Arcy/Watt model, which postulates the existence of high-affinity,low-affinity and multi-molecular water-binding sites. Desiccation-intolerantseeds younger than 25 DAA lacked the component of the absorptionisotherm characteristic of the high-affinity water-binding siteswhich have been hypothesized to confer desiccation tolerance.However, we were unable to determine whether the absence ofhigh-affinity binding characteristics was specifically relatedto desiccation intolerance or was artifactual due to the lossof volatiles when immature seed samples were dried at high temperatures. Key words: Muskmelon, embryo, germination, development, vigour, desiccation     

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     

Effect of abscisic acid on galactomannan degradation and endo-β-mannanase activity in seeds of Sesbania virgata (Cav.) Pers. (Leguminosae)

Seeds of Sesbania virgata (Cav.) Pers. (Leguminosae) have an endosperm which accumulates galactomannan as a storage polysaccharide in the cell walls. After germination, it is hydrolysed by three enzymes: α-galactosidase (EC 3.2.1.22), endo-β-mannanase (EC 3.2.1.78) and β-mannosidase (EC 3.2.1.25). This work aimed at studying the effect of abscisic acid (ABA) on galactomannan degradation during and after germination. Seeds were imbibed in water or in 10⁻⁴ M ABA, and used to evaluate the effect of exogenous and endogenous ABA. Tissue printing was used to follow biochemical events by detecting and localising endo-β-mannanase in different tissues of the seed. The presence of exogenous ABA provoked a delay in the cellular disassembly of the endosperm and disappearance of endo-β-mannanase in the tissue. This led to a delay in galactomannan degradation. The testa (seed coat) of S. virgata contains endogenous ABA, which decreases ca. fourfold during storage mobilisation after germination, permitting the galactomannan degradation in the endosperm. Furthermore, endo-β-mannanase was immunolocalised in the testa, which has a living cell layer. The ABA appears to modulate storage mobilisation in the legume seed of S. virgata, and a cause–effect relationship between ABA (probably through testa) and activities of hydrolases is proposed.     

Cauliflower (Brassica oleracea L.) Seed Vigour: Imbibition Effects

By means of a machine vision facility, the process of water-imbibitionin a small seeded brassica species was recorded as the visibleincrease in seed volume. Dry cauliflower seed (Brassica oleracea)showed an immediate rapid phase of imbibition upon the additionof water. This initial phase was associated with the reductionin seedling root growth resulting from the imbibition of coldwater, and the rate of uptake of water at 20?C was negativelycorrelated with subsequent seedling growth. Damage to the testaof dry seed resulted in an increased rate of imbibition anda corresponding decrease in seedling root growth measured onslant boards. This showed that the intact testa of cauliflowerseed is capable of acting as a barrier to water influx and thata high rate of water uptake is damaging to the embryo. Testadamage reduced percentage soil emergence of seeds, as did raisingthe soil moisture content during the imbibition period by wateringimmediately after sowing. Both these treatments were believedto increase imbibition rate. Conditions which encouraged a lowrate of water uptake also improved the rate and uniformity ofemergence. Correlation of mean imbibition rates (measured ina laboratory test) with soil-emergence indicated that the sensitivityto imbibition damage varied between seed lots and interactedwith the absolute rate of water influx to determine the finalpercentage emergence. This factor prevented reliable predictionof seedling performance from the ranked-order of measured imbibitionrates. The significance of these findings to the seed productionand modular transplant raising industries is discussed. Key words: Machine vision, imbibition rate, testa, soil moisture, vigour     

Effect of tannin content of faba bean (Vicia faba) seed on seed vigour, germination and field emergence

Differences in seed vigour of zero- and high-tannin faba beans were investigated using 25 seed lots of 12 cultivars following earlier reports of poor emergence in the zero-tannin types. Field emergence ranged from 54–96% indicating differences in seed vigour between cultivars all having high laboratory germination (>91%). Seed from zero-tannin accessions with poor emergence had a higher incidence of testa and cotyledon cracking, a smaller percentage of hard seeds, more rapid water uptake, a lower percentage of vital staining of cotyledons and a greater leaching of solutes than high-tannin types. Nevertheless, variation in these characteristics existed between cultivars and lines of both types. Seeds with more cracks in the seed coat and fewer hard seeds imbibed water more rapidly and consequently showed lower levels of vital staining and more cracks in the abaxial surface of the cotyledons. Slower imbibition in polyethylene glycol lessened the incidence of these deleterious characteristics and may provide a practical resolution to the problem of poor field emergence in zero-tannin lines of faba bean with low seed vigour.     

Some Aspects of the Reproductive Biology of Limonium vulgare Mill., and Limonium humile Mill.

The germination of two species of salt-marsh plants Limoniumvulgare Mill., and L. humile Mill., is investigated in relationto their ecology. Germination is inhibited by sea water, butgermination even in fresh water is low. Inhibition of germinationby sea water is negatively correlated with water uptake. However,a treatment in sea water stimulates subsequent germination infresh water. The effect of the sea-water treatment appears tobe one of osmotic shock which weakens the seed coat. Variationin response to the treatment is partly genetical and partlyenvironmental. Seeds in different parts of the salt-marsh willbe subject to differing conditions, both during seed developmentand during the interval between seed maturation and seed dispersal.In connection with this the effect of leaching by sea waterand fresh water is considered. The response to a sea-water treatmentvaries with time. Considered in the long term it shows somecyclical variation which might correspond with the tidal cycle.It is shown that seeds of Limonium can survive long periodsin sea water. There is a slow rate of germination during immersion.Most of those seeds which do not germinate in sea water surviveto germinate rapidly in fresh water. The response to oxygenconcentration, light, and temperature is also investigated.Experiments on seedling growth and establishment show the needfor fresh water and a suitable substrate. Mud gives a lowergermination but a higher survival, while sand gives a highergermination but a lower survival. The dispersal of Limoniumseeds in nature is investigated. Seeds of Limonium are mostabundant in the drift line, but even these only represent asmall fraction of the total produced. It is considered thatreproduction by seed is only important when a new area is beinginvaded. Subsequent reproduction is largely by vegetative spread.The ecological implications of the germination experiments arediscussed.     

Evidence for Repair Processes in the Invigoration of Seeds by Hydration

Seeds with low vigour as a result of ageing showed a large improvementin seed quality following a 2 h soak in water, reflected inan increased rate of germination, higher emergence in soil,and the retention of high germination after 24 h rapid ageingin a controlled deterioration vigour test. Similar, but smallerimprovements were seen after a priming treatment using polyethyleneglycol. Seeds dried to their initial moisture content aftertreatment retained these beneficial effects. The treatmentshad little effect on high vigour seed. These findings suggestthat seed invigoration by hydration treatments results fromthe repair of previously sustained deterioration. Brussels sprouts, Brassica oleracea var. gemmifera, priming, repair, seed moisture content, ageing     

Sowing seasons and drying methods during post-harvest influence the seed vigour of soybean (Glycine max (L.) Merr.)

Experiments were conducted to study the influence of sowing seasons and drying methods on the seed vigour of two spring soybean (Glycine max (L.) Merr.) cultivars. Two cultivars, ‘Huachun18’ and ‘Huachun 14’, were sown in three seasons viz., spring, summer and autumn and the harvested seeds were dried using three different methods. The results showed that soybean sown in spring had a higher number of branches per plant, pods per branch and seed weight, and consequently resulted in higher seed yields than that of soybean sown in autumn or summer seasons. Seeds sown in the autumn season had the lowest values of electrical conductivity during seed imbibitions, higher peroxidase (POD) activity in germinated seedlings and lower contamination by the seed-borne fungi on the MS medium, which indirectly improved the seed vigour, which was followed by summer sown seeds. Seeds sown during the spring season resulted in poor seed vigour. In addition, the effect of drying methods on the seed vigour was also clarified. Seeds that hung for four days before threshing and then air-dried had the poorest seed vigour which was determined by germination, electrical conductivity, POD activity and seed borne fungal growth. There was no difference in seed vigour between other methods, i.e. seeds threshed directly at harvest and then air-dried on a bamboo sifter or concrete floor. These results indicated that autumn sowing soybean and the drying method in which seeds were threshed directly at harvest and then air-dried on a bamboo sifter resulted in higher seed vigour.     

Moisture Loss as a Prerequisite for Seedling Growth in Soybean Seeds (Glycine max L. Merr.)

Rosenberg, L. A. and Rinne, R. W. 1986. Moisture loss as a prerequisitefor seedling growth in soybeanseeds (Glycine max L. Merr.).—J.exp. Bot. 37: 1663–1674. As soybean seeds [Glycine max (L.) Merr.] develop, they undergoa change in seed moisture. When excised prematurely from thepod and planted, seeds do not exhibit seedling growth until63 d after flowering (DAF) when the seed moisture has fallenbelow 60%. In contrast, seed germination (radicle protrusion)can occur when seeds as young as 35 DAF (68–79% moisture)are excised, but this germination docs not lead to comparableseedling growth frequencies unless seeds are first given a moistureloss treatment to artificially reduce their moisture below 60%.A moisture loss treatment applied at 35 DAF thus enables seedto undergo the transition from germination (cell expansion)to seedling growth (cell division and expansion) to the extentthat treated immature seed have a vigour index comparable toseeds matured on the plant (100%). The pattern of protein synthesisin vivo was examined in 35 DAF seed using [³⁵S]-methionine incorporation.When moisture loss treatment was applied for 24 h to 35 DAFseeds, seeds synthesized several new polypeptides when comparedwith untreated seeds at the same developmental stage. The sameseed samples showed 0% seedling growth in the absence of moistureloss treatment and 80% seedling growth when the treatment hadbeen applied. Moisture loss from soybean seeds appears to bea prerequisite for the synthesis of new proteins which may bepart of the metabolic process or processes that allow the soybeanseed to undergo the transition from seed germination to seedlinggrowth. Key words: Moisture loss, germination/growth, soybean     

聚乙烯醇预处理提高大豆种子活力和抗冷能力的作用

聚乙烯醇预处理大豆种子和聚乙二醇一样,能明显地提高种子的活力、萌发率和抗冷能力。其主要作用可能是:在整个吸胀过程中减少了吸水速度,使膜的修复作用有足够的时间;启动和改善种子内部的生理代谢过程.保证了生长胚根有更多的物质供应。     

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     

Evaluation of Seed Storage Conditions and Genetic Diversity of Four Crucifers Endemic to Spain

Traditional assays (germination and vigour), as well as biochemicalassays using isozyme loci, were performed to evaluate the effectof different seed storage conditions in Coincya rupestris, Iberispectinata, Moricandia moricandiodes and Vella pseudocytisus.Seeds had been stored for 24–30 years under long-term(LT) and short-term (ST) conditions. Fresh seeds of the samespecies from natural populations (NP) were also collected in1996 and used for comparison. Isozyme loci were used as markersof genetic deterioration and to determine the genetic diversityof samples. The germinability, vigour and enzyme activity ofLT samples were comparable to values obtained using freshlycollected NP samples, showing the effectiveness of the long-termstorage conditions. Copyright 1999 Annals of Botany Company Endemics, genetic diversity, germination, isozymes, seed ageing, seed storage, vigour.     

Germination Rate of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] Seeds Affected by Their Orientation

Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] seeds developwith the adaxial surface continuous with the cone scale. Onseparation, the scale side of the seed is lighter coloured andflatter than the side not previously in contact with the scale.Seeds oriented scale-side-up on a moist surface germinate morerapidly than seeds placed scale-side-down. When seeds were germinatedunder laboratory conditions, the response to orientation variedamong seeds of different geographic origin. Most of the geographicvariation in germination rate occurred when seeds were orientedscale-side-up. Pseudotsuga menziesii (Mirb.) Franco, Douglas-fir germination, orientation of seeds     

Seed Selection for Potential Viability

A simple method is presented for selecting individual seedsfor growth and vigour prior to germination. The selection isbased on the measurement of an electric current originatingduring the initial stage of seed imbibition. After selecting,seeds may be returned to the quiescent state without affectingviability. Results of both laboratory germination and fieldexperiments demonstrate that high germination rates, more extensivegrowth, higher yields, and fewer defective plants are associatedwith small currents. Seeds of low viability and high currentsmay be removed to upgrade the germination and vigour. Resultsare presented from several varieties of Phaseolus vulgaris andfrom three other plant species. Experiments are discussed whichindicate that seeds graded by current levels possess markedlydifferent respiration rates.     

The Role of Anaerobic Respiration in Germinating Muskmelon Seeds: I. IN RELATION TO SEED LOT QUALITY

Five muskmelon (Cucumis melo L.) cultivar seedlots from a commercialsource and freshly produced seeds of two cultivars, when artificiallyaged, were found to differ in their viability and vigour asdetermined by germination tests. Furthermore, the various commercialseedlots without ageing also exhibit a range of deteriorationlevels. Low vigour seeds had higher respiratory quotient valuesthan the high vigour seeds as a result of a higher level ofCO₂ production. This high level of CO₂ evolution in low vigourseeds may have been due to anaerobic respiration. Levels of acetaldehyde and ethanol produced by imbibing seedswere negatively associated with seed viability and vigour. After6 h of imbibition low vigour seeds produced significantly moreethanol and acetaldehyde than high vigour seeds. After 24 hof imbibition, ethanol continued to accumulate in the commercialseedlots up to 10-fold the amount produced after 6 h of imbibition,whereas, acetaldehyde levels increased less. However, in thefreshly produced, artificially aged seeds (except the most extremeageing), ethanol levels were reduced and no acetaldehyde productioncould be detected, indicating re-utilization of ethanol. It is suggested that ethanol production in the first hours ofimbibition can be used as a reliable index to predict germinationin muskmelon seedlots. Key words: Germination, Cucumis melo L., Seeds, Anaerobic respiration     

Osmoconditioning as a Means of Counteracting the Ageing of Pepper Seeds during High-temperature Storage

Sweet pepper seeds were osmotically conditioned in 0.4 M mannitolsolution for 4 d (at 25 °C, in darkness) before or afterstorage at 35 °C for up to six months, and their germinationand viability was compared with that of untreated seeds storedunder the same conditions. Seeds that had been osmoconditionedprior to storage retained a high rate of germination and germinatedto a high final percentage (from 80 to 50 per cent) at both15 and 25 °C throughout the storage period. By contrast,both the rate and total level of germination of untreated pepperseeds declined rapidly at both germination temperatures, andby three months of storage the total level of seed viabilitywas already less than 10 per cent. Seeds that were first storedat 35 °C, and then osmoconditioned just prior to germination,showed a decline in germinability which when tested at 25 °Cwas the same as for untreated seeds, while tested at 15 °Coccurred at a slightly slower rate than for untreated seeds. It is evident that osmoconditioning prior to storage, in additionto the acceleration of germination, resulted in a dramatic delayof the ageing rate, thus increasing considerably the longevityof seeds. On the other hand, osmoconditioning after storagedid not seem to have any significant effect on seed viability,though it enhanced the germination rate. Capsicum annuum, sweet pepper, seed, germination, osmoconditioning, priming, storage, viability, ageing, longevity