Effects of seed deterioration and seed-bed environment on emergence and yield of spring-sown barley

Seedling emergence from barley seeds, deteriorated by storage at supra-optimal moisture contents and temperatures, was adversely affected by sowing early in spring when soil temperatures were low, and by sowing into wet seed beds. There were significant interactions between seed lots of varying levels of deterioration and seed bed condition, because the more severely deteriorated lots emerged proportionately less well than the control, non-deteriorated lots. The yield results also showed significant interactions between seed lots and seed-bed condition because plants from deteriorated seeds in low populations resulting from partial emergence failure were unable to compensate and produce plot yields similar to those of higher populations.     

Studies on death of deteriorated barley seeds in soil

Seeds of barley cv. Golden Promise which had been deteriorated by storing at 20% moisture content and 30 °C and which all had viabilities >85% were treated with a slurry of calcium peroxide and with dusts of a mercurial and a non-mercurial fungicide. Calcium peroxide improved seedling emergence in wet soil conditions and deteriorated seeds benefited more than non-deteriorated seeds. The fungicide dusts had no effects. In controlled conditions at 20 °C, deteriorated seeds in wet soil died mainly within 2 days of sowing and they were more tolerant if they were placed in moist soil for 2 days before transfer to wet soil. Application of a mercurial fungicide and sterilizing the soil and the surface of seeds improved emergence but did not restore it to the level in moist soil. Fusarium culmorum, F. equiseti, Mucor spp. and Mortierella spp. dominated the fungus flora isolated from surface sterilised dead seeds in wet soil. When the fungi were inoculated to seeds, they increased the proportion which died in wet soil but only at high inoculum levels. It was concluded that they acted primarily as saprophytes depriving seeds of oxygen and secondarily as seed colonisers.     

The influence of anoxia and ethanol on barley seed death

Survival of deteriorated barley seeds in wet soil was improved by exposure to 70% oxygen compared with that in air and decreased by the imposition of anoxia. Deteriorated seeds were more sensitive to anoxia than non-deteriorated seeds, the former died within 4 days, while the latter survived more than 7 days. Ethanol accumulated in non-deteriorated seeds in wet soil conditions during the first 24 h and thereafter declined, while it increased to higher concentrations over 3–4 days in deteriorated seeds. High concentrations of ethanol were recorded in seeds in anaerobic conditions regardless of the level of deterioration. It was concluded that oxygen diffusion to the seeds was severely restricted in wet soil resulting in a switch to anaerobic respiration, the products of which, indicated by ethanol content, accumulated within the tissues. Non-deteriorated seeds tolerated higher concentrations of ethanol than deteriorated seeds and the coleorhiza extruded through the covering layers more rapidly facilitating gaseous exchange, while in the latter, anaerobic products accumulated to toxic levels.     

Nutrient content of Abutilon theophrasti seeds and the competitive ability of the resulting plants

Summary Siblings of Abutilon theophrasti, were grown on a nutrient gradient. The plants grown at higher nutrient levels were larger and produced larger and more seeds than plants grown at lower soil nutrient concentrations. There were no differences in germinability of seeds, but the competitive abilities of resulting plants were markedly different.In two different competition experiments designed to eliminate the effects of genotype, seed size, and germination time, by using synchronously germinated seedlings derived from similar size seed from plants grown at different nutrient levels, we found that plants from seeds produced at higher nutrient levels consistently, outperformed plants from seeds produced at the lower nutrient levels. The dominance of seeds produced at higher nutrient levels may be explained by the fact that they had markedly higher concentrations of nitrogen than did seeds produced at lower soil nutrient levels. The additional advantage of increased seed quality to plants controlling more of the nutrient resource than their neighbors would be expected to accelerate their contributions to the gene pool of the population.     

Changes in Growth,Developmment,and Physiological and Biochemical Activity of Asparagus Seedlings Grown from Space Flown Seeds

Asparagus seeds were sent on board retrievable satellites and they were flown in space for 8 days. Experiments were conducted in fields and laboratory after the seeds returned to the earth. Comparative studies were made on the growth and development patterns of plants growing from space flown seeds and controls kept on the earth. Changes in physiological and biochemical characteristic of the seedlings were also studied. The results obtained are summarized as follows: (1) Space flight markedly raised the germination rate of seeds as compared with the controls kept on the earth. After 5 days of imbibition, 40% of the space flown seeds germinated while the germination rate for ground controls was only 22.5%. After 6 days of imbibition the germination rate of space flown seeds was 65 % and that of ground controls 40%. After 10 days of imbibition, the rates rose to 87. 5% and 72. 5% respectively. The seedlings from space flown seeds grew in fields much faster than ground controls. The yield of tender stems of the former was 34% higher than the latter. (2) An assay on respiration showed that the respiratory intensity of space seedlings was 61% higher than that of ground controls. This indicated that the vigor of seeds enhanced under space conditions, accelerating the germination of seeds and growth of seelings. (3) The proline content of space seedlings was 33% higher than that of the ground controls. At the same time, the permeability of the plasma membrane of the space seedlings was markedly lower than that of the ground controls. The content of aspartic acid in plants grown from space seeds was slightly higher than in ground controls while the content of asparagus was markedly lower.     

Growth responses and fitness costs after induction of pathogen resistance depend on environmental conditions

Fitness costs of resistance are among the most widely discussed explanations for the evolution of induced resistance, but studies on induced resistance to pathogens are scarce and contradictory. In the present study the influence of nitrogen supply, length of the growing period and competition on the seed production of Arabidopsis in response to treatment with the chemical resistance elicitor BION^® was investigated. BION^® treatment elicited resistance to the bacterial pathogen Pseudomonas syringae, and biochemical changes after BION^® treatment were similar to those observed after bacterial infection. Induced plants grew more slowly during the first week after resistance induction, for which they then compensated by exhibiting faster growth than controls. Whether or not induced plants produced less seeds than controls depended on growing conditions. Costs, no costs and even higher seed production by induced plants were observed in experiments differently combining abiotic conditions. A higher seed production by induced plants arose particularly when the vegetation period was short, most probably a consequence of senescence-related processes that had been activated by resistance elicitation. Induced plants, however, produced less seeds when competing with controls and experiencing a full growing period. Studies controlling only some of the critical environmental factors can easily lead to apparently contradictory results, which in fact represent different outcomes of a complex interplay of factors.     

A Calorimetric Study of the Changes in Lipids during Seed Storage under Dry Conditions

Changes in the lipid constituents of seeds are believed to be associated with losses of seed viability during storage. The physical properties of lipids in seeds of genetically similar backgrounds but varying ages were compared using differential scanning calorimetry. The technique measures the temperature and energy associated with lipid-melting transitions and is noninvasive. Although differences in the temperature at which lipids melted were sometimes observed among deteriorated and fresh seeds, the direction of the change was inconsistent among species tested. For all species tested except tomato, there was a decrease in the energy associated with the lipid melt in deteriorated samples, and the change occurred at a similar rate as the loss of seed vigor. The data suggest that there are changes in the lipid components of seeds that are associated with seed deterioration and that these changes can be measured using differential scanning calorimetry.     

Pre-sowing magnetic treatments of tomato seeds increase the growth and yield of plants

The effects of pre-sowing magnetic treatments on growth and yield of tomato (cv Campbell-28) were investigated under field conditions. Tomato seeds were exposed to full-wave rectified sinusoidal non-uniform magnetic fields (MFs) induced by an electromagnet at 100 mT (rms) for 10 min and at 170 mT (rms) for 3 min. Non-treated seeds were considered as controls. Plants were grown in experimental plots (30.2 m(2)) and were cultivated according to standard agricultural practices. During the vegetative and generative growth stages, samples were collected at regular intervals for growth rate analyses, and the resistance of plants to geminivirus and early blight was evaluated. At physiological maturity, the plants were harvested from each plot and the yield and yield parameters were determined. In the vegetative stage, the treatments led to a significant increase in leaf area, leaf dry weight, and specific leaf area (SLA) per plant. Also, the leaf, stem, and root relative growth rates of plants derived from magnetically treated seeds were greater than those shown by the control plants. In the generative stage, leaf area per plant and relative growth rates of fruits from plants from magnetically exposed seeds were greater than those of the control plant fruits. At fruit maturity stage, all magnetic treatments increased significantly (P < .05) the mean fruit weight, the fruit yield per plant, the fruit yield per area, and the equatorial diameter of fruits in comparison with the controls. At the end of the experiment, total dry matter was significantly higher for plants from magnetically treated seeds than that of the controls. A significant delay in the appearance of first symptoms of geminivirus and early blight and a reduced infection rate of early blight were observed in the plants from exposed seeds to MFs. Pre-sowing magnetic treatments would enhance the growth and yield of tomato crop.     

Ethanol and acetaldehyde in imbibing soybean seeds in relation to deterioration

Deterioration as evidenced by decline in germination or seedling growth of soybean (cv. Essex) seeds during accelerated aging treatments at 41 C and 100% relative humidity is accompanied by increased levels of acetaldehyde and ethanol in imbibing embryonic axes and seeds. These increases become more pronounced with duration of the aging treatment. A similar inverse relationship between levels of acetaldehyde and ethanol and deterioration was observed when seeds were “naturally” aged for several years. During imbibition of low-vigor, accelerated-aged seeds at 25 C, acetaldehyde and ethanol increased from near trace amounts in dry tissues to maximum levels at 4 hours. Increases in acetaldehyde and ethanol during imbibition were less in high- than in low-vigor seeds. Increases were also less pronounced in low-vigor seeds when water uptake injury was avoided by osmotically decreasing water uptake rate with 30% polyethylene glycol. Embryonic axes from deteriorated seeds were characterized by low rates of O₂ uptake and high respiratory quotients relative to the unaged controls. Anaerobic conditions and respiratory inhibitors, such as sodium azide, increased acetaldehyde and ethanol in unaged seeds to levels similar to those in accelerated-aged seeds after 2 hours imbibition. It is suggested that, during aging, an imbalance between tricarboxylic and glycolytic activities, present during early imbibition to some degree even in vigorous unaged seeds, becomes more pronounced and leads to accumulation of ethanol and acetaldehyde.     

Beneficial effects of gamma-irradiation of quinoa seeds on germination and growth

Quinoa is one of the crops well-adapted to high altitude regions that can grow relatively well under drought, humid, and high UV radiation conditions. This study was performed to investigate the effects of gamma-radiation on quinoa. Seeds were treated with various doses of 50 Gy, 100 Gy, 200 Gy, 300 Gy, 400 Gy, 600 Gy, 800 Gy, and 1000 Gy. We investigated germination, as well as plant height, chlorophyll content, and normalized difference vegetation index (NDVI) at 0, 30, 44, 58, and 88 days after transplanting (DAT) and panicle weight at 88 DAT. The plants grown from the seeds treated at radiation doses greater than 200 Gy showed reduced values in most growth and physiological characteristics. The germination rate and germination speed were higher in the 50 Gy-treated seeds than in 0 Gy-treated (control) seeds. Plant height and panicle weight were highest in the plants from 50 Gy-treated seeds. Chlorophyll content was higher in all treated samples than in the controls. NDVI value showed the highest value in 0 Gy controls and plants treated with 50 Gy. The antioxidant activity was also higher in the plants from the seeds treated with 50 Gy and 100 Gy, showing a steady increase as the radiation dose increased even at 200 Gy. The plants from seeds treated with 0 Gy showed higher expression of proteins related to photorespiration and tubulin chains. The plants from seeds treated with 50 Gy induced more stress-responsive proteins.

     

VARIATION IN SEED WEIGHT AND ITS EFFECTS ON GERMINATION IN PASTINACA SATIVA L. (UMBELLIFERAE)

Pastinaca sativa (wild parsnip) produces seeds on the primary, secondary, and tertiary umbels of the flowering stalk. Within plants, variation in seed weight is about twofold. Secondary and tertiary seed weight is 73% and 50% of primary seed weight, respectively. Maximum variation in seed weight between plants is sixfold when tertiary seeds from a small plant are compared to primary seeds from a large plant. Within an umbel order, variation in seed weight between plants is correlated with plant size. Under autumn germinating conditions in the laboratory, final germination of seeds from different umbel orders does not differ but smaller seeds germinate more rapidly than larger seeds. Under spring germination conditions in the laboratory, significantly more primary and secondary seeds germinate than tertiary seeds and the rate of germination is independent of seed weight. Field germination of seeds from different umbel orders produces similar results except that in the spring both secondary and tertiary seed germination is lower than that of primary seeds. These results suggest that with respect to seed germination characteristics small seeds may have a competitive advantage over large seeds in the autumn because they germinate more quickly, but in the spring small seeds are at a disadvantage because they have lower overall germination. Because most germination in the field occurs in the spring, population recruitment from small seeds is likely to be substanially less than that from large seeds.     

Dynamics of storage reserve deposition during Brassica rapa L. pollen and seed development in microgravity

Pollen and seeds share a developmental sequence characterized by intense metabolic activity during reserve deposition before drying to a cryptobiotic form. Neither pollen nor seed development has been well studied in the absence of gravity, despite the importance of these structures in supporting future long-duration manned habitation away from Earth. Using immature seeds (3-15 d postpollination) of Brassica rapa L. cv. Astroplants produced on the STS-87 flight of the space shuttle Columbia, we compared the progress of storage reserve deposition in cotyledon cells during early stages of seed development. Brassica pollen development was studied in flowers produced on plants grown entirely in microgravity on the Mir space station and fixed while on orbit. Cytochemical localization of storage reserves showed differences in starch accumulation between spaceflight and ground control plants in interior layers of the developing seed coat as early as 9 d after pollination. At this age, the embryo is in the cotyledon elongation stage, and there are numerous starch grains in the cotyledon cells in both flight and ground control seeds. In the spaceflight seeds, starch was retained after this stage, while starch grains decreased in size in the ground control seeds. Large and well-developed protein bodies were observed in cotyledon cells of ground control seeds at 15 d postpollination, but their development was delayed in the seeds produced during spaceflight. Like the developing cotyledonary tissues, cells of the anther wall and filaments from the spaceflight plants contained numerous large starch grains, while these were rarely seen in the ground controls. The tapetum remained swollen and persisted to a later developmental stage in the spaceflight plants than in the ground controls, even though most pollen grains appeared normal. These developmental markers indicate that Brassica seeds and pollen produced in microgravity were physiologically younger than those produced in 1 g. We hypothesize that microgravity limits mixing of the gaseous microenvironments inside the closed tissues and that the resulting gas composition surrounding the seeds and pollen retards their development.     

Effects of decreasing source/sink ratio in soybeans on photosynthesis, photorespiration, transpiration and yield

Abstract. Shading of all side leaflets of a determinate soybean cultivar during pod filling significantly increased rates of photosynthesis in the unshaded centre leaflets, compared to centre leaflets of controls. Higher rates were associated with both higher stomatal and mesophyll conductances, and were reversible within 2 days when shades were removed. These higher rates of photosynthesis were not associated with decreased percentage enhancement by low oxygen, indicating that treatment effects were probably not associated with changes in photorespiration relative to photosynthesis. Percentage enhancement did, however increase as the plants approached physiological maturity, chiefly because of a decrease in photosynthesis.
In spite of these increases in rates of photosynthesis seed weight per plant was decreased by 37% in plants with side leaflets shaded for the entire pod-filling period and by 28% in plants shaded for only the second half of the period. In plants where shades were removed during the second half of pod filling seed yield was reduced by only 19% because shade removal delayed leaf senescence. The four treatments reduced yield by different mechanisms. Plants shaded continuously during pod filling produced fewer seeds than controls, but the weight per seed was similar. When shading was applied during the second half of pod fillings seed number was unchanged but weight per seed was significantly reduced. In contrast when shades were removed for the second half of pod filling, seed number remained similar to that of continuously shaded plants, but seed weight increased.
Although all shading treatments reduced yield, the reduction was not proportional to the 63% reduction in leaf area available for photosynthesis. This was because (1) photosynthetic rates in the centre leaflet of shaded plants were higher than rates in controls, (2) stem and lower surface photosynthesis in shaded leaf-lets contributed to whole leaflet photosynthesis.     

The effects of seed weight on growth and competitive ability of Rumex acetosella from two successional old-fields

Summary The effects of seed size on growth, biomass allocation and competitive ability of Rumex acetosella plants grown either individually or in competition were studied in two populations (6 months and 15 years old respectively) sampled from a postcultivation successional gradient. For plants grown individually there were highly significant effects of seed weight on growth after 43 days, with a higher relative growth rate (RGR) observed for plants raised from heavier seeds. However at the end of the experiment, seedlings developed from lighter seeds had a RGR 2 times greater than those from heavier seeds. Final biomass of the two types was not significantly different after 73 days of growth. When plants were grown individually, there were only slight differences between populations, but when grown in monocultures of 4 plants per pot, plants from the old population had higher root and leaf biomass per pot whereas those from the young population had a higher reproductive effort per pot. This suggests that a trade-off between allocation to sexual and vegetative reproduction occurs over successional time. In mixtures of light and heavy seeds, plants from light seeds were shorter, had fewer leaves and lower biomass than plants from heavy seeds, which were also taller and produced more dry matter than plants grown from heavy seeds in monoculture. The significant effects of seed weight and population on biomass parameters persisted unit the end of the experiment. Seedlings from heavy seeds were strong competitors: those from the young population grew better in the presence of neighbors than in monoculture and those from the late successional population suppressed the more the growth of their partners. Seedlings from light seeds were subordinate competitors. These results suggest that seedlings from seeds of different sizes benefit from contrasting ecological conditions and that selection acts on reproductive output along successional gradients.     

Methods for inoculating field crops with mycorrhizal fungi

Four methods were compared for inoculating red clover with selected mycorrhizal fungi when sown in a field containing an indigenous mycorrhizal population. The largest amount of mycorrhizal infection (around 65% of root length infected) was obtained by placing inoculum with the seeds in furrows. The inoculum used was standard soil inoculum from stock plant cultures spread by hand or the same inoculum concentrated to about one seventh by wet-sieving, and then fluid-drilled. The effectiveness of multiseeded pellets (seeds stuck onto pellets of soil inoculum) applied broadcast was more variable, infection ranging widely around an average of 30%. Applying both soil inoculum and seeds broadcast produced just under 10% infection, similar to that in the controls given autoclaved inoculum. Seedling establishment, in contrast, was-better where seeds were applied broadcast than in furrows. It seemed therefore that multiseeded pellets might be the best compromise for achieving reasonable infection in most plants, but fluid drilling had the advantages of greatly reducing the amount of inoculum needed and of readily combining seeds and inoculum in a single carrier.     

Reproduction and progeny of Silene latifolia (Caryophyllaceae) as affected by atmospheric CO2 concentration

Sexual dimorphism in plants has been known for over two millennia. However, little is known about how male and female reproduction of dioecious species will respond to anthropogenic environmental perturbations. Using growth chambers, the effects of CO(2) enrichment on male and female reproduction in Silene latifolia were examined and whether parental CO(2) environment affected progeny germination and sex ratio. Reproduction of male and female S. latifolia was enhanced by a similar magnitude at elevated CO(2). Over the growing season, males produced 16 times as many flowers as females did fruits per plant, but no difference in reproductive biomass between genders was observed at ambient or elevated CO(2). Germination of seeds produced by plants grown at different CO(2) concentrations was significantly different. Female seeds from higher CO(2)-grown plants tended to emerge earlier than those from ambient-CO(2)-grown plants, but emergence of male seeds was little affected. Overall, seeds from elevated-CO(2)-grown plants had 20% higher germination and were more female-biased than those from ambient-CO(2)-grown plants. Because of the enhanced reproduction and more female-biased progeny under elevated CO(2), the population structure of this cosmopolitan weedy species will likely be altered in a future environment.     

火柴头（Commelina benghalensis）实生植株资源配置及繁殖代价

火柴头具有地上和地下生殖枝开花结实的特性,产生地上大、小种子和地下大、小种子4种不同类型的种子.对4种类型种子实生植株的研究表明,4种类型种子实生植株个体水平上对新种群的贡献具有差异,地上大种子表现为最大,地下小种子则最小;4种类型种子实生植株在资源的繁殖配置上存在着差异,大种子尤其地上大种子对有性繁殖的资源分配最大,而地下小种子最小,这种差异又决定了在繁殖投资和繁殖代价上的差异,小种子特别是地下小种子实生植株的繁殖投资最小,而大种子特别是地上大种子实生植株的繁殖投资最大;从繁殖代价来看,大种子实生植株的繁殖代价之间差异不显著,而大种子实生植株的繁殖代价显著小于小种子实生植株的,地上小种子实生植株的繁殖代价显著小于地下小种子实生植株的.     

CONSEQUENCES OF EMERGENCE PHENOLOGY FOR REPRODUCTIVE SUCCESS IN RANUNCULUS ADONEUS (RANUNCULACEAE)

This study explores the effects of emergence time and reproductive phenology on seed number, seed size, and seedling survival in a population of the alpine buttercup, Ranunculus adoneus. Phenology in this snow bowl population is structured by snow depth. Plants in late melting interior portions of the bowl emerged and flowered 3 to 4 wk after those in early melting zones at the bowl perimeter during the summers of 1988 and 1989. Flowering time differences of buttercups across the bowl were consistent from one year to the next. In 1988, late flowering plants tended to set fewer seeds than early flowering ones; in 1989 no decrease in seed number accompanied flowering date. Path analysis showed that equal fecundity in early and late emerging portions of the bowl population during 1989 resulted from balancing spatial and temporal constraints on seed production. Spatial aspects of habitat quality improved toward the interior of the bowl, but temporal regimes deteriorated in these late melting sites. In both 1988 and 1989 seed size declined with delays in flowering. Path analysis of 1989 data showed that because of reduced time for seed growth, plants in late melting portions of the bowl set smaller seeds than those in earlier melting zones. Differences in seed size due to parental phenology are likely to influence fitness in snow buttercups. Under natural conditions, seedlings from large seeds (>;0.65 mg) have sixfold higher survival than do those from smaller seeds (<;0.65 mg). We conclude that seedling recruitment may be infrequent in late-melting portions of the snow bowl due to delayed parental phenology.     

Induction of Multiple Bud Clumps from Inflorescence Tips and Regeneration of Salt-tolerant Plantlets in Beta vulgaris

We developed an efficient method for sugar beet multiplication in vitro from excised immature inflorescence tips. On Murashige & Skoog medium supplemented with 4.4 μM 6-benzylamino- purine and 1.3 μM naphthaleneacetic acid, multiple bud clumps were induced from segments of inflorescence tips. The clumps proliferated rapidly. By radiation of small bud clumps at an appropriate dose and by directional selection for NaCl tolerance, we obtained salt-tolerant bud clumps and regenerated plantlets. The plants were vernalized and self-pollinated. The seeds of the regenerated plants were sown in pots of sand and irrigated every day with a solution of 342 mM NaCl. Some of the seeds germinated and grew normally in the 342 mM NaCl solution, exhibiting higher salt-tolerance than the control ones; such seedlings after the saline selection were transplanted to soil and the plants grew normally and produced plump root tuber similar to controls. The seeds from two selected lines germinated and grew for a few weeks in 513 mM NaCl solution before the seedlings withered. In saline soil where the salt concentration was about 154 mM, the yields of tuber from the plants of three salt-tolerant lines were about 45–50 tons ha⁻¹, approximately 2.6–2.9 times of the controls. It is concluded that we have got salt-tolerant materials with good agronomic traits for sugar beet breeding via selection in vitro.     

Further studies on seed transmission of broad bean stain virus and Echtes Ackerbohnenmosaik -Virus in field beans (Vicia faba)

Broad bean stain virus (BBSV) and Echtes Ackerbohnenmosaik-Virus (EAMV) were detected in the seed coat and embryo sac fluid of immature seeds from infected field beans (Viciafaba minor) by inoculation to Phaseolus vulgaris; BBSV was also detected in immature embryos. The proportion of seeds infected with either virus decreased during maturation. The viruses were transmitted to seedlings as often through fully ripened seeds from which the seed coats had been removed as through intact seeds. Both viruses were detected in pollen from infected plants, but in glasshouse tests only BBSV was transmitted through pollen to seeds. Delaying fertilization in plants infected with BBSV or EAMV seemed not to affect seed transmission of either virus. In glasshouse tests BBSV was transmitted more often through seeds from plants that were inoculated before flowering than during flowering, and was not transmitted through seeds from plants inoculated after flowering; EAMV was transmitted only through seeds from plants inoculated before flowering. In tests on seed from naturally infected plants BBSV was transmitted more often through seeds from plants that developed symptoms before flowering than during flowering. Both viruses were seed-borne in all cultivars tested and there was no marked difference in the frequency of transmission of either virus among the spring-sown cultivars most common in Britain. Both viruses persisted in seed for more than 4 yr.