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Abstract
Seed germination and respiration of peach [Prunus persica (L.) Batsch] were evaluated as potential preselection indices for predicting bud chilling requirement. Low chilling lines (Ã650 hours) germinated significantly earlier than high chilling lines, with an average r of 0.91 between cultivar chilling requirement and mean days to 80% germination at 4°C in 2 experiments. Based on germination behavior, differentiation between lines exhibiting small differences in chilling requirement was not feasible but separation into low and high chilling categories was possible. Removal of the testa resulted in earlier germination among all lines, but the order of germination remained consistent. An r of 0.84 was obtained between cultivar chilling requirement and mean days to 80% germination at 4°C using seeds with the testa removed. Respiration rate of seeds from 4 lines varying in bud chilling requirement with intact testa rose gradually during stratification. Seeds with the testa removed exhibited a rapidly increasing respiration rate during stratification. Respiration rate of seeds from low chilling lines exhibited a higher mean respiration rate than seeds from high chilling lines in seeds with the testa removed.
Abstract
Seed germination at 10°C in partially isogenic F5 lines of tomato (Lycopersicon esculentum Mill.) with varying low-temperature germinating abilities was negatively correlated with oleic acid levels and positively correlated with linoleic acid contents. Fatty acid composition did not change with time of incubation at 10°C, nor in the presence of activated carbon. Fatty acid composition of membrane-lipid fractions was similar to the total fatty acid of the seeds. The proportion by which linoleic acid is higher in cold-germinating lines (CG) is roughly the same as the amount by which oleic acid is lower in non-cold-germinating (NCG) lines. We suggest that gene regulation of cold-germinating ability is associated with a more extensive desaturation of oleic acid into linoleic acid during seed development.
Abstract
‘GL 659’ and ‘Vanguard’ lettuce seed lots germinated almost completely at 30°C when treated with ethephon (100 mg/liter). Similar treatment at 35°C failed to release seeds from dormancy. Kinetin treatment (10 mg/liter) at 35°C was only moderately effective in breaking heat dormancy, but when ethephon and kinetin were combined at this temperature, the interaction was synergistic and germination was almost complete. The preincubation time requirement at 25°C before maximum germination could occur after transferring to 35°C was nearly eliminated by treating seeds with the ethephon-kinetin mixture. ‘Calmar’ seeds, which had a lower heat tolerance, could not be induced to germinate completely at high temperature by any treatment.
Abstract
Seeds of 5 cultivars of lettuce (Lactuca sativa L.) were adjusted to moisture contents between 5 and 22% and subjected to temperatures of 5, -18, -70, and -196°C (liquid nitrogen) for 7 days. Seeds with moisture contents up to 18% were not damaged by either -18 or -196°C; however, the -70°C treatment resulted in loss of germination even with seeds containing as little as 16% moisture. Seeds held at 5°C showed no loss in viability. The loss in germination at -70°C appeared to be related to cooling rate. High moisture (18 to 20%) seeds were cooled to -196°C at different rates from 1 to 200°C/min. Germination was reduced in seeds cooled at rates slower than 25°C/min. At 200°C/min cooling rate and 18 to 20% seed moisture both germination and root growth occurred although at reduced levels compared with control seeds held at 5°C. Prolonged storage (33 days) in liquid nitrogen of rapidly frozen high moisture lettuce seeds did not result in further loss of germination after the initial freezing to -196°C.
Abstract
Seeds of tomato (Lycopersicon esculentum Mill.) and barley (Hordeum vulgare L.) on germination media were exposed to hydrogen chloride gas for 20 min. Seeds incubated and exposed on filter paper suffered developmental effects which were dependent on gas concentration. While germination rate was slightly reduced for sensitive seeds at the higher concentrations, suppression of seedling growth was evident at all levels of HCl tested. There was little effect on either germination or seedling length in seeds exposed and incubated on soil. Filter paper and soil adsorbed HCl during 20-minute exposures in proportion to gas concentration, but the soil apparently buffered most adverse reactions of the acid.
Abstract
Seed germination of pepper (Capsicum annuum L.) in aerated water columns was accelerated and germination uniformity improved by using gibberellic acid (GA3) at 6 μg/mg seed with 50 to 75 mg seed/ml of solution. Higher GA3 rates in the aerated columns reduced germination percentage in some cultivars. Detrimental effects for GA3 up to 6 μg/mg seed were not observed and in some cultivars speed of emergence and seedling growth was stimulated. GA3 is economically feasible for use in germinating pepper seeds for sowing using the fluid drilling technique.
Abstract
Slow and inconsistent germination of cyclamen, Cyclamen persicum Mill., seed appeared to be more related to seed and seedling vigor than to any type of seed dormancy. Pregermination and germination seed treatments such as immersion in hot water, still and flowing water, cool moist storage, alternating temperatures and fungicide treatments were of little value. Treatment with gibberellin (GA) solutions accelerated germination but created an expelled embryo problem. The grower is advised to surface disinfest fully imbibed seed in 5% sodium hypochlorite for 20 sec to 1 min.
Abstract
Cultivars of 5 highbush (Vaccinium corymbosum L.) and 5 rabbiteye (Vaccinium ashei Reade) blueberries were each pollinated with a series of cultivars of varying genetic relationship. A significant reduction in mean berry weight was associated with an increase in the degree of relationship between parents for one highbush and one rabbiteye cultivar. The mean number of seed per berry was significantly reduced and was associated with an increase in the degree of relationship for 3 highbush and 2 rabbiteye cultivars. Level of inbreeding did not affect percentage seed germination. Two highbush cultivars demonstrated a significant reduction in mean seedling fresh weight associated with an increase in the level of inbreeding. Rabbiteye seedling vigor data were insufficient to draw any conclusions on inbreeding effects. Variability of cultivars in response to cross-pollination among related individuals suggests that other factors may be more influential in some instances.
Abstract
Seed germination was 90–95% for Kentucky coffeetree [Gymnocladus dioicus (L.) C. Koch] after concentrated sulfuric acid treatment for 120 to 150 minutes; 97–98% for honeylocust (Gleditsia triacanthos va. inermis L.) following 60, 90, or 120 minutes concentrated sulfuric acid scarification; and was 67–72% for redbud (Cercis canadensis L.) after 30, 60, or 90 minutes of concentrated sulfuric acid scarification followed by a 60-day stratification period. Scanning electron micrographs of acid-scarified Kentucky coffeetree, honeylocust, and redbud seed indicated that lumens of the macrosclereid cells on the seed surface were exposed after acid treatment, permitting imbibition of water. Boiling water treatment ruptured the macrosclerid layer, while seed treated with liquid N2 had fissures that did not appear to penetrate the macrosclereid layer.
Seeds in fruit of bell pepper (Capsicum annuum `California Wonder') plants grown in nutrient solutions deficient in potassium (<3 mmol·L-1) showed a higher incidence of sprouting (i.e., vivipary) than seeds in fruit from plants grown at adequate potassium levels (6 mmol·L-1). Tissue analysis showed a progressive drop in the leaf content of potassium with increasing plant maturation for all levels of potassium nutrition. However, potassium in fruit and seeds increased at later stages of maturity. ABA was extracted, isolated and identified from bell pepper seeds obtained from fruit grown under the potassium treatments (0.0, 0.6, 1.5, 3.0, and 6.0 mmol·L-1) at five fruit maturity stages (mature-green to overripe). At early fruit maturity stages, there were no significant differences in seed ABA content in the fruit from the different potassium treatments. However, differences in ABA content and vivipary among the potassium treatments became highly significant as the fruit matured. The concentration of ABA in seeds of potassium-deficient treatments was ≈14% of the control (0.4 versus 2.8 μg·g-1 dry mass). High concentrations of ABA in bell pepper seeds were associated with low incidence of vivipary and high potassium content in the leaves, fruit and nutrient solution.