Search

Indian ricegrass, Oryzopsis hymenoides(Roem. & Shult.) Ricker is an important forage crop in the western United States. The seeds of this species are dormant at harvest and even following several years of storage. In spite of several attempts by various workers to uncover the factors responsible for dormancy, little progress has been made to date. The present investigation was undertaken to reexamine in detail the nature of dormancy in these seeds with emphasis on the effects and possible roles of hormones in release of dormancy. The seed coats of Indian ricegrass seeds prevented germination and were shown to delay the uptake of water, gibberellic acid, and tetrazolium salts by the seed. The acid scarification proved the only effective method of breaking dormancy imposed by the seed coats. One‐year‐old scarified Indian ricegrass seeds were also shown to exhibit a post‐harvest dormancy which was overcome by 10 μMgibberellic acid and 10 μMkinetin. Intact seeds contained abscisic acid and the level of this inhibitor decreased following scarification. Gibberellic acid was incorporated into scarified Indian ricegrass seeds by acetone permeation suggesting a commercial preparation for these seeds.

While it is commonly accepted that the Occurrence of excess soil water following planting adversely affects the establishment and early growth of corn (Zea maysL.) seedlings, the effect of flooding duration, soil temperature at time of flooding, and cultivar have not been determined. Such information would be useful to drainage system designers and corn breeders. The objective of this study was to determine whether pregermination flooding duration and soil temperature at time of flooding affect the emergence of selected inbred and hybrid corn cultivars. Five popular inbred [A632, B37, B73, H60, and Mo17] and five hybrid [(A635 ✕ A632)Mo17, B73 ✕ H60, (H95 ✕ H99) A632, (OH514 ✕ OH7B)H95, Mol7 ✕ B73] corn cultivars grown in Ohio were exposed immediately following planting to differing durations of flooding (0,48,96, and 144 h) at two temperatures (10 and 25 °C) in the laboratory and at cold (near freezing) and warm (approximately 25 °C) temperatures in a silty, clay, loam Typic Argiaquoll soil in the field. Seedlots were selected which possessed a germination percentage above 90. Laboratory and field results showed inbred cultivars to be more tolerant of flooding than hybrid cultivars. Flooding damage as measured by reduced emergence was noted in both inbred and hybrid cultivars after only 48 h flooding in both laboratory and field studies. The severity of flooding damage was enhanced for both cultivar groups when flooding temperature was increased from 10 to 25 °C.

Indian ricegrass, Oryzopsis hymenoides(Roem & Shult.) Ricker, seeds are dormant at harvest and show a coat‐imposed as well as an embryo dormancy. In this investigation we report on the relationship of the two types of dormancy to changes in certain enzymes implicated in seed germination and seedling growth. Scarification with concentrated sulfuric acid followed by hormonal treatments released both types of dormancy. The removal of seed coat was essential for germination and for the induction of peroxidase, α‐amylase, and ribonuclease activities. Marked quantitative differences were found in cathodic isoperoxidases from intact and scarified seeds as early as 24 hours after imbibition suggesting their involvement in pregermination processes. Hormones had little effect on peroxidases. Inhibitor studies indicated that all isoperoxidases with the exception of one might be synthesized de novo. The enhancement of α‐amylase and ribonuclease by gibberellic acid and kinetin in scarified seeds occurred only after 24 hours. This result suggests, that gibberellin or cytokinin modulation of these enzymes might be post‐germination events and that seeds are presumably deficient in these hormones. Qualitative and quantitative changes were not detected in isoribonucleases of intact seeds. The differences in isoribonucleases between hormone treated and untreated scarified seeds appeared only after 24 hours. The enhancement of RNA polymerase activity by chilling in intact seeds at zero time and in scarified seeds at 24 hours may be due to gene derepression directly related to the release of embryonal dormancy.

Early planted corn (Zea maysL.) is frequently subjected to flooding stress, especially in poorly drained soils. This study characterizes the role of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) enzymes in the flooding susceptibility of corn seeds; PDC and ADH activities were assayed in a flood‐tolerant (A632) and a flood‐susceptible (Mo17) inbred during flooding at 10 and 25 °C. Each inbred consisted of two seed lots possessing different germination levels (95 and 75% germination). Flooding induced an increase in the activity of both enzymes. However, the increase was greater and sustained longer for ADH than PDC. The maximum level of ADH activity achieved was similar in both inbreds, but was greater in the high‐quality than in the low‐quality seeds. Since the highquality seeds survived flooding longer than the lowquality seeds, no correlation between flooding susceptibility and maximum ADH activity was observed. The two inbreds also exhibited similar ADH isoenzyme patterns. These data indicate that flooding susceptibility is not associated with PDC or ADH activities in corn seeds.

A substantial increase in the number of soybean [Glycine max(L.) Merr.J cultivars has occurred in recent years. Many of these are derived from a narrow genetic base, which makes traditional cultivar identification increasingly difficult. As a result, new techniques that detect minor biochemical differences need to be evaluated for their ability to differentiate among cultivars. This study examines the applicability of reversed phase high performance liquid chromatography (RP‐HPLC) for soybean cultivar identification. Salt soluble proteins of 14 cultivars were extracted from unimbibed seeds, eluted from a reversed phase C4 column with increasing concentrations of acetonitrile, and monitored at 280 nm. Seeds were obtained for study from three differing growing locations in Ohio. While no qualitative differences of elution profiles were detected within cultivars and locations, comparisons of quantitative RP‐HPLC seed protein profiles permitted separation of genetically diverse genotypes. Retention time ratios for selected peaks were not significantly different among cultivars, but peak area percentage showed that quantitative differences were useful criteria for distinguishing closely related lines. This study documents that RP‐HPLC analysis of soybean seed proteins can distinguish divergent soybean genotypes and suggests that peak area percentage of RP‐HPLC profiles is a superior method of cultivar analysis.

Efficient management of seed stocks depends on an accurate description of seed longevity in storage. This work was conducted to study the implementation of the probit analysis method of modeling seed deterioration. Samples of field bean seed (Phaseolus vulgarisL.) were stored at eight temperatures (20‐60°C) and four moisture levels (12–24 g H2MO kg−1) from 0 to 372 d, and evaluated using the standard germination test. Probit analysis was applied to the entire data set simultaneously using nonlinear regression as well as the conventional environment by environment approach. Nonlinear regression was performed on the germination angles using the model statement: germination angle = arcsin√Φ[ki− p/10(Ke−CwLogM−ChT−CqT2)] where Φ is a function that computes the probability that a random variable with a normal (0,1) distribution falls below the argument of the function; Kiis a seedlot constant, and Ke, Cw, Ch, and Cqare species constants. Regression yielded the following parameter estimates: Ki= 6.68 (95.4% initial germination), Ke= 9.08, Cw= 5.20, Ch= 0.0057 and Cq= 0.00079. Use of these parameters resulted in a fit (R2= 0.83) comparable to that obtained by the conventional environment by environment approach (R2= 0.80). Persistent lack of fit of deterioration curves to the normal distribution model occurred in both approaches. When probit analysis was performed by environment, specifying the initial germination of the seedlot as the natural response rate, linearity of the probits over time was significantly improved. This suggests that probit analysis of seed deterioration should be performed specifying a natural response rate (6% initially dead seeds in this case) if the initial germination is below 100%

Field bean (Phaseolus vulgarisL.) seeds represent an important nutritional component of the diets of many people in developing countries. Yet yields of this high‐protein crop are typically much less in developing compared with developed regions. Seed quality is difficult to maintain in developing countries and can influence the growth and yield of many crops. This study evaluated the seed quality effect on emergence, plant growth, yield, and N2fixation of ‘Pompadour Checa’ field bean. Both naturally and artificially (1, 2, and 3 d at 41 °C and 100% RH) aged seeds were planted in 1984 and 1985 in a Crosby silty clay loam (fine, mixed, mesic Aerie Ochraqualf) with an organic matter content of 3 to 5%. Percent emergence and normal seedlings decreased while percent abnormal seedlings increased with increasing seed deterioration. Plant growth was evaluated at the V3, R6, and R8 growth stages. Decreasing seed quality generally culminated in less top and root growth and less seed yield. Decreased seed yield was attributed to fewer seeds produced per plant, since no significant decrease in seed weight was observed. Seeds of lower quality also produced plants with fewer nodules, less nodule weight, and less dinitrogen fixation as determined by the acetylene reduction assay. The observed differences in plant vegetative and reproductive growth from seeds differing in quality may be associated with their ability to successfully form root nodules and fix N.

Soybean [Glycine max(L.) Merr.] seeds are prone to imbibitional injury, which may culminate in significant economic losses. This study was designed to investigate the regulation of soybean seed imbibition by the seed coat. The intact seed coat delayed water uptake in the embryonic axis, cotyledons, and whole seed during the first 8 h soaking. The seed coat also assisted in tangential as well as radial displacement of water to the embryo. Scanning electron micrographs revealed a seed coat‐derived radicle pocket surrounding the radicle tip as well as hourglass cells in the seed coat, which decreased in size away from the hilum. The function of the radicle pocket and hour glass cells of the seed coat may be associated with water storage surrounding the embryonic axis. This is substantiated by the large water‐holding capacity of the seed coat compared to its fresh weight. Isolated seed coats absorbed 3.8 times their fresh weight in water. These studies ascribe a significant role to the seed coat in regulating embryo moisture uptake. Initially, the seed coat retards water uptake and/or governs the direction of water penetration to the embryo and eventually serves as a reservoir of water for the hydrating axis.

Seed imbibition is a critical stage in successful soybean [Glycine max(L.) Merr.] crop establishment. This study investigatesoybean seed imbibition with emphasis on absorption of water by the seed parts (seed coat, embryonic axis, cotyledons, and whole seed). Mter 72 h imbibition, the embryonic axis was the most hydrated portion of the seed possessing greater than 50 g kg−1fresh weight more water than any other seed part. The embryonic axis also hydrated more than the cotyledons in a high relative humidity environment when exposed as separated parts. Using polyethylene glycol 8000 as an osmotic agent, the seed coat, cotyledons, and whole seed contained a moisture content of approximately 550 g kg−1fresh weight and the embryonic axis 700 g kg−1fresh weight when germination (radicle emergence but less than 1.0 cm in length) occurred. while the cotyledons and embryonic axes of accelerated aged seeds did not differ in liquid moisture uptake from nondeteriorated seeds, the axes from accelerated aged seeds absorbed less water than the unaged controls when the seed parts were hydrated at 100% relative humidity (RH). These studies show that the embryonic axis hydrates more than the cotyledons, identify the level of moisture in the embryonic axis at which soybean seed germination is observed, and indicate that deteriorated seeds hydrate in a manner similar to nondeteriorated seeds in liquid water but that differences in the axes are detectable when hydrated in a high humidity environment.

Historically, days after flowering (DAF) has been the criterion for sampling developing soybean [Glycine max(L.) Merr.] seeds. Seed development rate, however, differs according to genotype and environmental conditions, leading to variable DAF values for the same seed development stage. Morphologically described growth stages (GS), in contrast, allow a rapid and convenient sampling method for seed development and composition studies. The purpose of this study was to categorize the changes in mass and composition of developing ‘Williams 79’ soybean seeds at five reproductive GS. Seed mass and composition studies demonstrated that R5 and R7 were accurate indicators of seedfill initiation and physiological maturity (PM), respectively. At R5, diy weight, protein, oil, and sugar quantity were low, while moisture content was high. Moisture content decreased slowly between R5 and R7, while seed dry weight, protein, oil, and sugar content increased. Between R5 and R7, 97% of the seed dry weight at maturity had accumulated. Monosaccharides represented 82% of the seed soluble carbohydrates at RS, but decreased to 8% by R6. Sucrose increased two‐fold between R5 and R6, then remained at a high level until R8. Raffinose and stachyose were undetectable until R7, when they represented 11 and 34% of the total soluble sugar, respectively. The largest increase in fatty acid quantity occurred between R5 and R6. Palmitic, stearic, and linolenic acid accounted for 68% of the total fatty acid at R4, but only 21% at R6. Oleic and linoleic acid accumulated most rapidly between R5 and R6, representing 79% of the fatty acid content at R6. Four acetate buffer soluble proteins were resolved by electrophoresis at R5 and eight at R6. Banding patterns remained constant between R6 and R8, while protein quantity of Bands 2 through 8 decreased. The quantity (mg seed−1) of each macro‐ and micro‐element increased at varying rates between R5 and R7. After R7, the seed moisture content decreased rapidly while the quantity and composition of stored components changed little. At harvest maturity (R8), seeds possessed 380 g protein, 230 g oil, and 160 g sugar kg−1dry weight. These data serve as a useful characterization of changes in seed composition for future studies employing GS.