Changes in developing pea (Pisum sativum) seeds in relation to their ability to withstand desiccation

In two separate experiments in 1970 and 1971 the germination ability of seeds that had been rapidly desiccated following harvesting from glasshouse-grown pea plants improved with time after fertilization. In 1970 the germination of seeds directly after harvesting also improved with time. In both years the readiness with which electrolytes were leached from dried seeds decreased with seed age, measured as time after fertilization. The germination ability of desiccated seeds, and of undried seeds in 1970, improved after the cessation of seed moisture increase on the parent plant. This improvement coincided, in 1970, with a fall in the readiness with which electrolytes could be leached from seeds and with a decline in the rate of oxygen uptake of seeds directly after harvest. Vital staining of dried seeds from harvest samples indicated the viability of the samples as determined by germination tests. In both years, when the cotyledons first showed complete staining, the staining was very intense; in 1970 this occurred in a harvest sample with a greater than 50% germination level, but in 1971 it occurred in a sample that showed incomplete staining in the embryo axis and less than 5 % germination. In 1971 the comparative rates of moisture loss from seeds, measured with a sensor element diffusion porometer, were very low at 25 days after fertilization, increased up to a peak at 35 days and fell to a rate at the final harvest (44 days) which was nearly three times faster than the initial rate. Thus, during the period of dehydration, after 37 days, the seeds were able to lose moisture. When seeds were allowed to lose moisture slowly after harvest, before being desiccated rapidly, their eventual condition as measured by leaching improved. Also, the faster the initial water loss preceding rapid desiccation the more readily were the dried seeds leached. It is suggested that seeds can only withstand rapid desiccation after the cessation of moisture increase and after some slow dehydration, which is accompanied by a slowing down in physiological activity.     

The influence of abscisic acid on different polysomal populations in embryonal tissue during pea seeds germination

The influence of abscisic acid (ABA) on the processes of formation of different polysomal populations, their structures and stability in embryonal tissue during pea seeds germination was studied. The contents of total ribosomal fraction increased in all samples up to 72 h of germination and then decreased. The contents of polysomal population (FP, MBP, CBP and CMBP) extracted from the embryonal tissue after 72 hrs of germination of pea seeds were then quantified. It turned out that in examined tissue of control sample, fraction of free polysomes (FP) was the most abounded. This population of polysomes in sprouts decreased after ABA treatment. FP content decreased even more when the higher ABA concentration was applied during germination. Similar changes were observed in the fraction of membrane-bound polysomes (MBP). Quite different tendencies were found, however, in forming population of the cytoskeleton-membrane-bound polysomes (CMBP). The CMBP population content in embryonal tissue increased in a dosage dependent manner with increasing concentration of ABA applied during seed germination. This indicates the important role of CMBP fraction in synthesis of specific proteins in embryos in the time when processes of seeds germination are retarded by ABA. In the final part we examined the stability of polysomes isolated from sprouts of germinating seeds in water and sprouts isolated from seeds treated with ABA (100 μM) during germination. Total polysomes isolated from embryonal tissue of germinating seeds treated with ABA showed much higher resistance to exogenous ribonuclease digestion than total polysomes of control sample. The obtained results suggest that ABA influence on different polysomal population formation also controls their stability.     

Geographic variation in the flood-induced fluctuating temperature requirement for germination in Setaria parviflora seeds

Our aim was to search for specific seed germinative strategies related to flooding escape in Setaria parviflora, a common species across the Americas. For this purpose, we investigated induction after floods, in relation to fluctuating temperature requirements for germination in seeds from mountain, floodplain and successional grasslands. A laboratory experiment was conducted in which seeds were imbibed or immersed in water at 5°C. Seeds were also buried in flood-prone and upland grasslands and exhumed during the flooding season. Additionally, seeds were buried in flooded or drained grassland mesocosms. Germination of exhumed seeds was assayed at 25°C or at 20°C/30°C in the dark or in the presence of red light pulses. After submergence or soil flooding, a high fraction (>32%) of seeds from the floodplain required fluctuating temperatures to germinate. In contrast, seeds from the mountains showed maximum differences in germination between fluctuating and constant temperature treatment only after imbibition (35%) or in non-flooded soil conditions (40%). The fluctuating temperature requirement was not clearly related to the foregoing conditions in the successional grassland seeds. Maximum germination could also be attained with red light pulses to seeds from mountain and successional grasslands. Results show that the fluctuating temperature requirement might help floodplain seeds to germinate after floods, indicating a unique feature of the dormancy of S. parviflora seeds from floodplains, which suggests an adaptive advantage aimed at postponing emergence during inundation periods. In contrast, the fluctuating temperature required for germination among seeds from mountain and successional grasslands show its importance for gap detection.     

Bimodal changes in germinability of pea seeds under the influence of low doses of gamma-radiation

Pea seeds (cv. 'Nemchinovskii-85', harvest of 2002, 80%-germination percentage) were exposed to gamma-radiation with doses ranging from 19 cGy to 100 Gy. One week after the irradiation with doses of 19 cGy and 3 Gy. the germination percentage decreased to 58 and 45%, respectively; at doses of 7 and 10 Gy it was 73 and 70% respectively. At greater doses (25, 50, and 100 Gy), germination percentage decreased in proportion. Anomalous changes in seed germination percentage (as a function of irradiation dose) were caused by the redistribution of irradiated seeds between fractions I and II. The measurements of room temperature phosphorescence in air-dry seeds and the phosphorescence of endogenous porphyrines of imbibing seeds showen that the germination decrease after the irradiation with low doses (19 cGy and 3 Gy) was caused by the increase in the number of weak seeds of fraction II, which had high rates of water uptake and suffered from hypoxia under seed coat. Some of these seeds suffocated from hypoxia, and other seeds produced seedlings with morphological defects (such seeds were considered incapable of germination). During storage of seeds irradiated at doses 19 cGy-10 Gy, the recovery of germination percentage (after its initial decrease) was caused by the decrease in seed number in fraction II. The subsequent germination decrease was caused by seed death. The higher was the irradiation dose, the faster were changes in germination percentage during storage of irradiated seeds. Bimodal changes in pea seed germination with the increase of y-irradiation dose has apparently the same origin as the changes in seed germination during accelerated ageing.     

Investigation of the relationship between seed leachate conductivity and the germination of Brassica seed

Large differences in the leachate conductivities of single seeds after 24 h soaking were observed in five Brussels sprout cultivars. Within each cultivar non-germinable seeds tended to have higher conductivities than germinable seeds, but the conductivity above which seeds failed to germinate varied between cultivars. No conductivity reading or partition value could therefore be considered as an absolute boundary between germinable and non-germinable seeds to allow the prediction of seed germination for all seed lots of the same species. However, the mean conductivity for each sample was significantly correlated with germination (r = 0.83, P < 0.05) and was clearly higher for samples with lower germinations. Differences in the partition values for the five cultivars may have been attributable to the natural age of the seeds. Seeds of Asmer Aries artificially aged rapidly at 20% moisture content for up to 48 h at 45° C showed increasing leachate conductivity with increased time of ageing (r = 0.97, P < 0.01) and decreased germination (r = - 0.88, P < 0.05). Again however the values for germinable and non-germinable seeds of different artificial ages varied. Leakage from seeds was limited by the testa in the first 6 h of imbibition. Solute leakage from embryos of the five cultivars was therefore greater than those for intact seeds but a clear separation of germinable and non-germinable seeds was still not possible from the conductivity readings. The implications of the observed increases in conductivity with increased seed age and decreased germination for the development of a rapid vigour test for small seeded vegetables in conjunction with controlled deterioration are discussed.     

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.     

STIMULATION OF GERMINATION IN RICE (ORYZA SATIVA L.) BY A STATIC MAGNETIC FIELD

This study evaluates the percentage and rate of germination of rice (Oryza sativa L.) seeds, when exposed to magnetic treatment in laboratory conditions. The seeds were exposed to 150 and 250 mT magnetic fields both chronically and for 20 min after seeding. Nonexposed seeds were used as control. Chronic exposure to a 150-mT magnetic field increased (p < 0.05) both the rate and percentage of germination relative to nonexposed seeds (18% at 48 h). Significant differences were also obtained for seeds exposed to a 250-mT magnetic field for 20 min (12% at 48 h). Additionally, seeds were moistened with water magnetically treated by static and dynamic methods. Dynamic and static treatment of water improved the germination of seeds related to the control, but significant differences (p < 0.05) were only obtained for the dynamic method (16% at 48 h).     

快速打破结缕草种子休眠方法的比较

用水和30%NaOH对结缕草(Zoysia japonica Steud.)种子进行浸种处理,筛选能快速打破结缕草种子休眠的方法.结果表明:用水浸种6d,8d内发芽率仅为14.70%;用30%NaOH浸种120min,8d内发芽率也仅达28.00%;而用水浸泡2d后再用30%NaOH处理40min,8d内结缕草种子的发芽率达到了82.00%.说明用水和30%NaOH综合处理的方法可以快速有效打破结缕草种子休眠,缩短发芽周期,达到快速出苗的目的.     

A method for profiling classes of plant hormones and their metabolites using liquid chromatography-electrospray ionization tandem mass spectrometry: an analysis of hormone regulation of thermodormancy of lettuce (Lactuca sativa L.) seeds

A highly selective and sensitive method for the simultaneous analysis of several plant hormones and their metabolites is described. The method combines high-performance liquid chromatography (HPLC) with positive and negative electrospray ionization-tandem mass spectrometry (ESI-MS/MS) to quantify a broad range of chemically and structurally diverse compounds. The addition of deuterium-labeled analogs for these compounds prior to sample extraction permits accurate quantification by multiple reaction monitoring (MRM). Endogenous levels of abscisic acid (ABA), abscisic acid glucose ester (ABA-GE), 7'-hydroxy-abscisic acid (7'-OH-ABA), phaseic acid (PA), dihydrophaseic acid (DPA), indole-3-acetic acid (IAA), indole-3-aspartate (IAAsp), zeatin (Z), zeatin riboside (ZR), isopentenyladenine (2iP), isopentenyladenosine (IPA), and gibberellins (GA)1, GA3, GA4, and GA7 were determined simultaneously in a single run. Detection limits ranged from 0.682 fmol for Z to 1.53 pmol for ABA. The method was applied to the analysis of plant hormones and hormonal metabolites associated with seed dormancy and germination in lettuce (Lactuca sativa L. cv. Grand Rapids), using extracts from only 50 to 100 mg DW of seed. Thermodormancy was induced by incubating seeds at 33 degrees C instead of 23 degrees C. Germinating seeds transiently accumulated high levels of ABA-GE. In contrast, thermodormant seeds transiently accumulated high levels of DPA after 7 days at 33 degrees C. GA1 and GA3 were detected during germination, and levels of GA1 increased during early post-germinative growth. After several days of incubation, thermodormant seeds exhibited a striking transient accumulation of IAA, which did not occur in seeds germinating at 23 degrees C. We conclude that hormone metabolism in thermodormant seeds is surprisingly active and is significantly different from that of germinating seeds.     

Recovery of cassava (Manihot esculenta Crantz) plants from culture of immature zygotic embryos

An embryo culture protocol using immature cassava seeds has been developed to enhance successful seed germination and reduce time for population establishment. Embryonic axes were excised from seeds 40 days after pollination and placed on 1/3 MS medium supplemented with growth factors. Fruits were either air-dried at 20 °C to aid dehiscence, or dissected immediately after harvest. Culture of embryonic axes from seeds obtained from mature fruits (90 days after pollination) served as control. Average percent germination and plantlet recovery rate were higher for embryos cultured from non air-dried immature seeds than from air-dried immature seeds. Immature seeds that were air-dried before germination had ≥50% reduction in germination rate and ≥75% reduction in plantlet recovery rate, indicating that cassava immature zygotic embryos are susceptible to osmotic pressure changes. Genotypic effects were observed in shoot elongation, formation of internodes, and vigor of cultures from both mature and immature seeds. The high percentage of plants recovered from immature seeds through embryo culture opens up opportunities for genetic stock development in cassava that has been previously unexplored. This revised version was published online in June 2006 with corrections to the Cover Date.     

Enhanced symbiotic seed germination of Cypripedium macranthos var. rebunense following inoculation after cold treatment

Cypripedium macranthos var. rebunense is a well-known wild orchid in Japan, and is considered to be a symbol for rare plant conservation. A fungus isolated from roots of C. macranthos var. rebunense induced symbiotic germination of the species in vitro. Cold treatment of the seeds at 4°C prior to fungal inoculation was required for the symbiotic germination. Changing the timing of inoculation of the fungus to the seeds greatly improved germination frequency. Maximum germination was attained after seeds were inoculated just after the cold treatment for 12 weeks, and approximately 20% of the seeds developed into protocorms more than 1 mm long. These results suggest that fungal inoculation takes place at the beginning of spring in nature, and the tough impervious seed coat may preserve the seed from the infection during autumn and winter seasons. The lengthy culture period of more than 16 weeks at 20°C on the same medium with the fungus caused gradual browning and rot of the protocorms. By elimination of the fungus with a fungicide and by transfer to a nutrient rich medium, approximately 20% of the protocorms developed into healthy plantlets. The methods obtained here appear to be applicable to symbiotic germination of many other threatened Cypripedium spp.     

Analysis of the Effect of Light and Temperature on the Fluence Response Curves for Germination of Rumex obtusifolius

Both red light (10 minutes) and 35°C treatment (60 minutes) stimulate the germination of seeds of Rumex obtusifolius otherwise maintained in darkness at 25°C. Fluence response curves were determined for the effect of red light to stimulate germination of seeds with and without 35°C treatment. The endogenous far-red absorbing form (Pfr) level in the seeds was determined using short saturating fluences of wavelengths of light which maintain different proportions of phytochrome as Pfr at equilibrium. In the seed batches investigated, the endogenous Pfr level was found to be 4% or less of the total phytochrome. High dark germination after 35°C treatment does not result from an increase in sensitivity of the whole population to Pfr. Calculated fluence response curves for germination which best fit the experimental data suggest that seeds germinate in darkness after 35°C treatment because of a nonphytochrome-related process (overriding factor).     

A convenient screening test system and a model for thermal germination responses of wild plant seeds: behaviour of model and real seeds in the system

Abstract A convenient test system for screening the thermal germination behaviour of seeds was developed for both basic and applied research in seed germination ecophysiology. Only two temperature-controlled facilities, a test period of about a month and a relatively small number of sample seeds arc needed to obtain information on the thermal-germination parameters of individual seed populations, such as lower or higher limit temperatures, and thermal times required for germination. In the test system, the germination performances of sample seed populations were compared under two temperature regimes: a gradually increasing temperature regime and a gradually decreasing temperature regime, in which the seeds were subjected to gradually changing temperatures in the range of 4 36°C. In order to assess the effects of various values for thermal-germination parameters on the patterns of germination performance in the system, the behaviour of model seeds characterized by a definite set of thermal germination parameters were investigated. Referring to the results of the simulations, the actual germination patterns of some wild-seed populations in the test system were interpreted in terms of thermal-germination parameters.     

After-Ripening in Festuca idahoensis Seeds: Adaptive Dormancy and Implications for Restoration

Festuca idahoensis (Idaho fescue) was a common native perennial bunchgrass in the sagebrush steppe of the western United States until the introductions of domestic livestock and alien plants. Restoration of Idaho fescue to degraded sites will likely involve reseeding, and one of the factors affecting reseeding success is germinability of the seeds employed. We investigated effects of after-ripening and storage temperature on germinability of Idaho fescue seeds collected from a central Oregon site. Six months of after-ripening were required before maximum germination was obtained. Storage of dry seeds at either room temperature (20°C) or at cooler, alternating temperatures (5/15°C) did not alter the rate at which dormancy was lost. Storage at the warmer temperature promoted rapid germination in seeds that had broken dormancy. Seed longevity varied greatly from year to year. Seeds produced in a very dry year had poorer germination and shorter longevity than seeds produced during a year with near normal precipitation. Because seed dispersal occurs in late July and early August for Idaho fescue in central Oregon, a six-month after-ripening requirement ensures that the greatest potential germination coincides with the spring period most likely to provide sufficient moisture for seedling establishment.     

A method for seedling recovery in Jatropha curcas after cryogenic exposure of the seeds

Actually, the germplasm of Jatropha spp. is conserved as whole plants in field collections. Under this storage method, the genetic resources are exposed to disease, pest and natural hazards such as human error, drought and weather damage. Besides, field genebanks are costly to maintain and with important requirements of trained personnel. Thus, the development of efficient techniques to ensure its safe conservation and regeneration is therefore of paramount importance. In this work we describe a method for Jatropha curcas seeds cryoexposure and seedling recovery after thawed. In a first experiment, an efficient protocol for in vitro plant recovery was carried out using zygotic embryo or seeds with or without coat. In a second experiment, desiccated seeds with or without coat were exposed to liquid nitrogen and evaluated after cryoexposure. Germination percentages were variable among treatments, and seeds demonstrated tolerance to liquid nitrogen exposure under certain conditions. Seeds of J. curcas presented up to 99.6% germination after seed coat removal. Seeds with coat cultured in vitro did not germinate, and were 60% contaminated. The germination of the zygotic embryos was significantly higher in the 1/2 MS medium (93.1%) than in WPM medium (76.2%), but from zygotic embryo, abnormal seedlings reached up to 99%. Seeds with coat exposed to liquid nitrogen showed 60% germination in culture after coat removal with good plant growth, and seeds cryopreserved without coat presented 82% germination, but seedlings showed a reduced vigor and a significant increase in abnormal plants. Seeds cultured in vitro with coat did not germinate, independently of cryoexposure or not. This study reports the first successful in vitro seedling recovery methodology for Jatropha curcas seeds, after a cryopreservation treatment, and is recommended as an efficient procedure for in vitro plant recovery, when seeds are conserved in germplasm banks by low or cryotemperatures.     

In vitro culture and precocious germination ofTaxus embryos

Summary The lengthy dormancy requirement of yew seeds can be overcome with a simple in vitro method. Viable embryos were excised from seeds ofTaxus brevifolia and four cultivars ofT. media over a range of developmental stages. Embryos were cultured in several basal media formulations (Whites’, Gamborg’s B5 and Murashige and Skoog’s) under dark or light. After a lag period of 1 to 2 wk, embryos of both species germinated precociously. Germination rates of up to 70% were obtained withT. media cv. Hicksi embryos. The highest rates of germination were obtained in White’s and MS media. Embryos excised from green seeds with undeveloped arils showed the highest germination rates. As the seeds approached maturity, in vitro germination rates of the excised embryos declined dramatically. Green seeds and seeds with developing arils could be stored at 5° C without large loss in embryo germination. Seeds with fully developed arils could be stored frozen at −20° C for 1 wk while still allowing about 50% of embryo germination. At least 30% of the precociously germinated embryos of both species were able to develop into full seedlings. Our method appears to be generally applicable toTaxus spp. This research was supported by a grant from the Hawaii Biotechnology Group, Inc.     

Light and temperature action in germination of seeds of the empress tree (Paulownia tomentosa)

Seeds of the empress tree ( Paulownia tomentosa Steud.) were imbibed for two weeks in darkness at constant temperatures (18, 23 or 28°C), and then irradiated with red light for 5 min. Germination was poor if it took place at the same temperature as imbibition, but a high percentage was achieved if the seeds were exposed to higher or lower temperatures before they were irradiated. Maximum germination was obtained when the difference between pretreatment and imbibition was about 10°C. The effect increased with the duration of the pretreatment and was optimal at 24 h. The effect decreased as the time lapse between temperature pretreatment and red light irradiation increased, and it was lost after two days. If pretreatment was shorter than 24 h (12 h). a high percent of germination was obtained by alternating pretreatment and imbibition temperatures. The germination of seeds imbibed in 40% heavy water was also stimulated by temperature pretreatments. Light and temperature also exhibited an interactive effect in the germination of seeds that were imbibed in darkness for only 3 days. For each of the germination phases there was a temperature at which the time needed for 50% germination was the shortest, namely 35°C during imbibition, 37.5°C in the period of P_fr activity. and 32.5°C during radicle protrusion. The data obtained are shortly discussed in relation to the domestication of empress tree in Southern Europe.     

Timing for the planting method using deciduous forest topsoil in suburban Tokyo,Japan

The suitable time for planting using the topsoil of a warm temperate deciduous forest is discussed based on the germination characteristics of the soil seed bank. Forest topsoil was collected regularly over a 1-year period from a deciduous forest in suburban Tokyo, and seedling emergence in the outdoors was recorded immediately after collection. Many seedlings were observed from February to May, indicating that this is the best time for planting because this is when most buried seeds germinate. Additionally, it was inferred that buried seeds germinate immediately after planting during the period from February to October, although the quantity of seed germination varies according to the season. The method of evaluating the forest topsoil as a planting material is also discussed. The simple and preferred method of evaluation is to examine outdoor seedling emergence from February to May. Accurate evaluation during the summer and autumn months proved problematic, especially when counting tree seeds, and it was necessary to continue the evaluation into the following spring. A practical understanding of the timing of planting and the method of evaluating forest topsoil as a planting material is possible in warm temperate areas.     

小叶兜兰的种子发育和无菌萌发

为建立小叶兜兰的繁育技术体系,本研究通过无菌播种的方法,辅以TTc生活力测定等方法,比较了小叶兜兰种子在授粉后不同发育时期和培养条件下的萌发率,对小叶兜兰种胚的发育过程进行了显微观察,探讨种胚发育程度与萌发的关系。结果表明,小叶兜兰种胚的发育阶段对萌发的影响最大,授粉后255d的种子萌发率最高（90．71％）,该阶段种子仍呈白色但微干燥,种胚刚发育至球形胚阶段,胚柄尚存。1／4MS和1／2MS为小叶兜兰适宜的基本培养基,添加100mg·L^-1的土豆汁对小叶兜兰的无菌萌发有良好的促进作用。     

The dynamics of indole-3-acetic acid in Acer platanoides seeds during stratification and germination

During stratification at 5°C indole-3-acetic acid (IAA) levels in embryos of Acer platanoides decreased during the early stages but subsequently increased again throughout the remainder of a 144 day period. The reduction in IAA levels in embryos of fruits stored at 17°C was even more pronounced, and in addition, no increase was observed after longer storage periods at this temperature, the levels of IAA remaining very low. Germination in seeds maintained at 5°C was not observed until after 120 days or longer, but germination potential increased at an earlier stage, as shown by the fact that seeds transferred to 20°C gave appreciable increases in germination after much shorter chilling periods. Endogenous IAA levels in embryos from seeds transferred to 20°C after a chilling period, long enough to break dormancy, increased within 24 h, i.e. before visible germination, to levels similar to those observed in embryos from seeds chilled continuously for 144 days. Embryos from seeds chilled for 120 days, i.e. when the samples already showed visible germination and when the endogenous IAA content was already high, showed no further increase in endogenous IAA during a three day incubation at 20°C. None of the treatments employed was effective in inducing germination of seeds or embryos from fruits stored at 17°C.