Seed Maturation in Soybeans (Glycine max L. Merr.) is Independent of Seed Mass and of the Parent Plant, Yet is Necessary for Production of Viable Seeds

Freshly harvested seeds of soybean (Glycine max L. Merr.) orseeds shelled, then dried, were non-viable. Seeds dried in intactpods, even when only 17% of normal size, matured into viableseeds and produced healthy plants. These seeds maintained activityof various enzymes but gained little soluble protein while air-dryingin intact pods. There was a qualitative change in seed proteinsassociated with maturation. Seeds matured in intact pods havea greater proportion of protein as slow-moving bands and havecompletely lost one fast-moving band compared with seeds shelledbefore drying. Seed maturation is a distinct phase of seed production,is independent of the parent plant, and can be imposed on theseed at many stages of development.     

Occurrence of Multiple Forms of {alpha}-Amylase and Absence of Starch Phosphorylase in Soya Bean Seeds

Soya bean cultivars ‘Altona’ and ‘Chestnut’have active but quite low levels of -amylase. Activity was assayedwith specific substrates, oxidized amylose and ß-limitdextrin, which were resistant to attack by ß-amylase.During seed development -amylase activity increased to a maximumin both cultivars and then declined towards maturity. Matureand germinating seeds retain low activities of -amylase. Gelelectrophoresis separated the -amylase activity into six majorbands which occurred in both cultivars. The isozyme patternwas quite similar for developing, mature and germinating seed.although the relative proportion of activity in the variousbands changed somewhat. Starch phosphorylase was not detectedin any soya bean seed samples tested, but good activity wasfound in potato tuber extracts used as a control. Mixing experimentsusing soya bean and potato extracts indicated there were noinhibiting factors in soya bean seed extracts. Soya bean seedextracts probably do not contain starch phosphorylase. Glycine max (L.), Merr, soya bean, -amylase, isozymes, phosphorylase     

Starch Deposition and Carbohydrase Activities in Developing and Germinating Soya Bean Seeds

Immature soya bean seeds accumulate starch as a transient reservematerial which is utilized later in development. Germinatingseeds also accumulate starch reserves, probably as a resultof gluconeogenesis from storage lipid. Developing beans showa rapid increase in ß-amylase activity which continuesinto early germination before declining. Distribution of ß-amylaseactivity is not consistent with its supposed role in starchdegradation. Soya bean seeds also contain -amylase and -glucosidaseactivities which could be responsible for starch mobilization. Glycine max (L.) Merr., soya bean, starch, carbohydrase, amylase, -glucosidase     

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     

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     

Arrested Leaf Abscission in the Non-Abscising Variety of Pubescent Birch: Developmental,Morphological and Hormonal Aspects

A novel type of abscission development, arrested abscission,is described for a rare variety of pubescent birch (Betula pubescensEhrh. f. hibernifolia Ulvinen), the leaves of which dehydrateand remain attached to the plant. Anatomical examination ofthe abscission zone revealed that its development is temporallyand spatially similar to that of normal leaves of Betula pubescens.Floodingand exogenous ethylene were effective in inducing shedding ofthe leaves at the beginning of the growing season, butthis effectwas lost in senescing leaves. Leaf hydration and abscissionwere retained in the presence of external abscisic acid (ABA)inthe non-abscising variety, which also had a lower level of endogenousABA. The observed responses together with the alteredhormonallevel in this variety suggest that apart from ethylene, ABAis involved in autumnal abscission indirectly by regulatingtheleaf water status. Key words: ABA deficiency, abscisic acid, abscission zone, ethylene, senescenc     

Freezing exposure releases bud dormancy in Betula pubescens and B. pendula

Bud dormancy in woody plants is released by long-term exposure to non-freezing chilling temperatures, whereas freezing temperatures have been considered to have little or no effect. However, the present results demonstrate that short-term exposure to freezing can release bud dormancy in Betula pubescens (Ehrh.) and B. pendula (Roth). Short-term freezing during the dormancy induction phase improved the release of bud dormancy only if an adequate level of dormancy had been reached. In fully dormant or chilled plants both the percentage and the speed of bud-burst increased, the more so the lower the temperature. Our results rule out the possibility that endogenous abscisic acid could be directly involved in the physiological control of bud dormancy release. The fast, easily applicable method presented here for bud dormancy release could further investigations into the biochemical and biophysical background to the process. The mechanisms of bud dormancy release and its relationship to cold acclimation are discussed in the light of these results, as also are the implications of the findings for modelling of bud dormancy.