Morphological and Anatomical Studies of Linaria Species from South-west Spain: Seeds

Seeds of 24 taxa of Linaria from south-west Spain were examinedwith a scanning electron microscope and light microscope. Basedon seed features such as shape, surface ornamentation and cellshape, seven morphological types were recognized. Seeds of thedifferent types are described, illustrated and compared. A keyto distinguish the different species or groups of species isprovided. Copyright 1999 Annals of Botany Company Seed-coat, SEM, anatomy, Scrophulariaceae, Antirrhineae, Linaria .     

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     

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     

Effect of Matric-Priming Duration and Priming Water Potential on Germination of Four Grasses

In this study, a matric-potential control system was used todetermine the effect of matric-priming duration and primingwater potential on the germination response of Bouteloua curtipendula(Michx.) Torr., Cenchrus ciliaris L., Eragrostis lehmannianaNees, and Panicum coloratum L. Seeds were primed at water potentialsof –1·5 to –7·7 MPa for up to 14 d.Optimum germination generally occurred in treatments primedat high water potential for the shortest period. Germinationof seeds primed at lower water potential and for longer periodsexhibited a negative germination response relative to the control.Seeds were not redried after the priming treatment. Seed-wateruptake measurements suggest that a reduction in the lag timeof imbibition accounted for at least some germination-rate enhancementin the positive-priming treatments Key words: Germination, matric-priming, imbibition     

Formation of Multiple or Adventive Embryos in Epidendrum nocturnum Jacq (Orchidaceae)

Under greenhouse conditions, Epidendrum nocturnum Jacq. plantsproduce fruits by both self-fertilization and cleistogamy. Althoughadapted to these reproductive processes the species respondalso to cross-pollination. Seeds without embryos and with oneembryo are usual but occasionally seeds with two, three or fourembryos are produced. Multiple embryos are formed by polyembryonyand apomixis. Epidendrum nocturnum, self-pollination, cleistogamy, apomixis, polyembryony, supernumerary embryos     

Seed Water Relations and the Regulation of the Duration of Seed Growth in Soybean

Soybean [Glycine max (L.) Merrill] seeds and cotyledons weregrown in an in vitro culture system to investigate the relationshipsbetween cell expansion (net water uptake by the seed) and drymatter accumulation. Seeds or cotyledons grown in a completenutrient medium containing 200 mol m^–3 sucrose continueddry matter accumulation for up to 16 d after in planta seedsreached physiological maturity (maximum seed dry weight). Seedor cotyledon water content increased throughout the cultureperiod and the water concentration remained above 600 g kg^–1fresh weight. These data indicate that the cessation of seeddry matter accumulation is controlled by the physiological environmentof the seed and is not a pre-determined seed characteristic.Adding 600 mol m^–3 mannitol to the medium caused a decreasein seed water content and concentration. Seeds in this mediumstopped accumulating dry matter at a water concentration ofapproximately 550 g kg^–1. The data suggest that dry matteraccumulation by soybean seeds can continue only as long as thereis a net uptake of water to drive cell expansion. In the absenceof a net water uptake, continued dry matter accumulation causesdesiccation which triggers maturation. Key words: Glycine max (L.) Merrill, solution culture, duration of seed growth, water content, dry matter accumulation     

Effects on Phytochrome Controlled Germination Produced by Far-Red Irradiation of Seeds Before and During Rehydration

Seeds irradiated with red light and then re-dried will respondto this light treatment on subsequent rehydration in the dark.If such high-Pfr seeds are irradiated in the dry state withfar-red light immediately before rehydration the percentagegermination is significantly reduced in the case of Plantagomajor and Sinapis arvensis but increased in Bromus steriliswhere Pfr inhibits germination. This effect of far-red lightcan be reversed by red light despite the fact that red lightalone has no effect on dry seed. This is due to the interconversionof Pfr and the red light absorbing phytochrome intermediatecomplex meta-Fa. If there is a delay between far-red irradiationand rehydration of Sinapis seeds, the inhibitory effect of thefar-red irradiation becomes progressively less the longer thedelay. This reduction in effectiveness of far-red is interpretedin terms of a dark reversal of meta-Fa to Pfr with a half-lifeof about 4–6 h. The reappearance of Pfr is either veryslow or docs not occur in dehydrated Plantago seeds, as far-redtight given 96 h prior to hydration is just as inhibitory asfar-red light given immediately before hydration. Meta-Fa doesappear to revert to Pfr in darkness in Bromus seeds, but onlyvery slowly. The rapid increase in effectiveness of red irradiationduring rehydration of high-Pfr Plantago seeds suggests that,in this species, the pre-treatment used in preparation of high-Pfrseeds may increase the receptivity or amount of the Pfr reactionpartner. Key words: Phytochrome intermediates, Seeds, Germination     

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.     

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.     

The Interrelationship of Canavanine and Urease in Seeds of the Lotoideae

Seeds of 29 species of canavanine-synthesizing legumes wereassayed for their urease and canavanine production. All of theexamined species possess detectable urease activity. In general,the leguininous seeds richest in urease also had the most canavanine. The urease content of the jack bean seed, Canavalia ensiformis(L.) DC., is formidable and disproportionally greater than thequantity of stored canavanine. The massive urease content ofthe seed cannot be rationalized by the magnitude of the canavaninepool. Analysis of eight species of Mucuna demonstrated that canavanineis not stored in the seeds of these plants. Mucuna species donot appear to be unique in having seeds that do not concurrentlyproduce urease and canavanine.     

Effect of Endogenous Coumarin on the Germination of Seeds of Coumarouna odorta Aublet

Seeds of Coumarouna germinate readily at 33?C in darkness orlight in spite of high levels of endogenous coumarin. The concentrationof coumarin on a dry-weight basis remained constant in the cotyledonsand increased in the embryos during germination. Applied coumarin(0.4 and 4 mM) did not inhibit germination of Coumarouna butenhanced the growth of embryos; yet a single seed of Coumarouna,placed at the centre of a Petri-dish, drastically inhibitedgermination of other neighbouring seeds (lettuce, radish, andtomato). The presence of coumarin in the soil of potted seedlingssuggest that coumarin exuded by the radicle can inhibit germinationand growth of other species in its vicinity, thus eliminatingcompetition during the first stages of growth.     

Influence of Morphactin on Sex Expression in Luffa acutangula Roxb

Seeds of Luffa acutangula were soaked in aqueous solution ofmorphactin (25 mg/1) at 5° C for 5, 15, and 45 d. Such treatmentscaused highly significant reductions in the production of staminateflowers and increased the number of pistillate flowers.     

Germination Experiments with Seeds of a Segregate of Plantago major and their Bearing on Germination Studies

Experiments are reported on the germination of over 6, 000 seedsof a large strain of Plantago major. The freshly ripened seedsare shown to exhibit varying degrees of natural dormancy thatis gradually lost in contact with the soil and more quicklyin air. Germination is naturally intermittent, the germinationflushes being associated with the more-marked fluctuations oftemperature. Seeds stored for five months germinated in a quasi-simultaneousmanner. The results emphasize the importance of sowing freshlyripened seed from individual plants when assessing biologicalbehaviour.     

Influence of Salinity and Temperature on the Germination of Haloxylon recurvum Bunge ex. Boiss.

The stem succulent perennial halophyteHaloxylon recurvum Bungeex. Boiss. grows and produces seed under highly saline conditionsand seeds are deposited in saline soils. Experiments were conductedto determine the effect of salinity and temperature on the germinationof seeds. Results indicate that seeds can germinate at veryhigh salt concentrations (500 mM). However, highest germinationpercentages were obtained in distilled water. Cooler thermoperiodspromoted germination, while high temperatures significantlyinhibited the germination of seeds at all NaCl concentrationstested. Rate of germination decreased with increases in salinity.At higher thermoperiods the rate of germination was significantlylower in comparison to lower thermoperiods. Seeds recover afterbeing transferred to distilled water and recovery was higherfrom higher salinity concentrations and lower thermoperiods.Final recovery germination percentages in high salt treatmentswere significantly lower than non-saline controls, indicatingthat exposure to high concentration of NaCl permanently inhibitedgermination. Germination; halophyte; Haloxylon recurvum recovery of germination; salinity; temperature     

Desiccation of Phaseolus vulgaris Seeds During and Following Germination, and its Effect Upon the Translatable mRNA Population of the Seed Axes

Misra, S. and Bewley, J. D. 1986. Desiccation of Phaseolus vulgansseeds during and following germination, and its effect uponthe translatable mRNA population of the seed axes.—J.exp. BoL 37: 364–374. After imbibition and germination, seeds of P. vulgaris passfrom a stage where they are insensitive to desiccation to astage where they are sensitive. Desiccation of seeds duringthe sensitive stage results in an almost total impairment ofprotein synthesis upon subsequent rehydration. Seeds desiccatedduring the desiccation-tolerant stage, however, resume proteinsynthesis at almost control levels. The protein patterns obtained following in Vitro translationof bulk RNA from fresh imbibed, desiccated, and desiccated-rehydratedseed axes were qualitatively similar at 5 HAI (the desiccation-tolerant stage). The drying treatment resulted in increasedintensity of extant proteins at 5 and 12 HAI. At 12 HAI (thetransition stage between the desiccation-tolerant and desiccation-intolerantphases) desiccation and subsequent rehydration triggered synthesisof a unique set of proteins-the rehydration proteins. At 20HAI (the desiccation-intolerant stage) desiccation resultedin an overall decline in the intensity of proteins synthesizedin vitro. Also the rehydration proteins were not synthesizedin response to a drying and rehydration treatment at this time. Key words: Seed germination, desiccation, mRNA, in vitro translation, Phaseolus vulgaris     

Glaucium flavum Seed Germination - an Ecophysiological Approach

The yellow horned-poppy Glaucium flavum Crantz shows a finaldark germination which is of characteristically ‘mediterranean’type (maximal response at the temperature range 5–15 °C),though a considerable broadening is brought about, both by ared light pulse and a stratification treatment. Seeds imbibedin darkness at 25 °C for even a few hours are induced todevelop a secondary dormancy (thermodormancy) which can be releasedby light and stratification. The well known time dependenceof light sensitivity and the gradually imposed induction oflight indifference at supraoptimal temperatures have also beenshown. Seeds imbibed under regimes simulating those met naturallyin Greece during November or April, do not germinate when illuminatedwith white light (     

Gibberellin-induced Changes in Ultrastructure of Lettuce Cotyledons

Seeds of lettuce (Lactuca saliva L. cv. Grand Rapids) were incubatedin water or in gibberellin A₃ (GA). Some ultrastructural differencesbetween the cotyledons of 145 hour-old seedlings resulting fromthese two treatments are reported. The cotyledons of GA-treatedseedlings contained many plastids with poorly developed grana,while the control cotyledons contained only well-developed plastids.The frequency of grana in developed chloroplasts was also reducedby the hormone treatment. Effects of GA on the nucleus includeda decrease in heterochromatin and an increase in nucleolar volume.After GA treatment, the nucleolar matrix had a largely fibrillarappearance in contrast to the predominantly granular structureof the control nucleoli. Ultrastructural changes are discussedin relation to the GA-induced variations in the biochemicalcomponents previously reported.     

Characterization of the Germination Responses of Silene dioica (L.) Clairv., Populations from Europe

Germination tests were done on 20 populations of Silene dioicacollected in different parts of Europe. Seeds collected fromwild plants and from their progeny growing at R.B.G. Kew, weretested using both freshly harvested and stored seeds. Responseswere compared from tests done on thermo-gradient bars and inincubators to examine germination and after-ripening processesbetween c. 2-c. 45 °C. The responses of different populations were characterized byidentifying variations due to the proportions of dormant seeds,the maximum and minimum temperatures favouring germination,and the time course of germination at particular temperaturesof freshly shed and stored seed. Germination and after-ripeningresponses of different populations displayed marked qualitativesimilarities, but differences in the degree of their expressionresulted in statistically significant quantitative differenceswhich could sometimes be correlated with features of the geographicaldistribution of the populations. The results are discussed in relation to the occurrence of thisspecies in a well-defined natural habitat in Europe, and itis concluded that they represent a situation in which fundamentallysimilar control patterns underlying the responses of every populationexamined are modulated quantitatively to produce variationsin the number of seeds germinating at particular seasons orremaining dormant within the soil.     

Comparative Studies of Seed Germination of two Newly Isolated Lines of Grand Rapids Lettuce

Two lines of Grand Rapids lettuce were isolated by self-pollinationof single plants. Seeds of one line, designated ‘A’,germinate in the dark at 25 °C. Seeds of the second line,designated ‘B’ germinate in a manner typical oftheir variety. The lines differ in sensitivity to red (R) andfar-red (FR) light, in the ability of their seeds to overcomeresistance of an external osmotically active medium, in theresponse of mature seeds to abscisic acid, and in the responseof young seeds to gibberellin and benzyl adenine. ‘A’seeds germinate faster than ‘B’ seeds in the darkor after R or FR irradiation.     

Effect of red, far-red radiations on germination of cotton seed

Seeds of two cultivars, H-14 and J-34 of Gossypium hirsutumL. soaked in the dark for durations of 8, 12 and 16 hr wereexposed to red and far-red radiations alone and in differentsuccessions. While cv. J-34 was unresponsive to all light treatments,seed germinaiton in cv.H-14 was promoted by darkness and byexposure to far-red radiation and was inhibited by red andwhitelight.Seed germination depended upon what treatment was given at theend. The effect ofred light was reversed by far-red and viceversa. Although instances of light inhibition of seed germinationare known, the authors are not aware of any clear cut instancein the literature on far-red promotion of seed germination (Received November 4, 1970; )