Allen D. Knapp

Seed priming with brassinolide improves lucerne (Medicago sativa L.) seed germination and seedling growth in relation to physiological changes under salinity stress

Salt stress is an important constraint to lucerne (Medicago sativa L.) production in many parts of the world. Seeds of 3 lucerne varieties, cvv. Victoria, Golden Empress, and Victor, were used to investigate the effects of seed priming with 5 µm/L brassinolide on germination and seedling growth under a high level of salt stress (13.6 dS/m NaCl solution). The results showed that germination percentage, germination index, and vigour index of lucerne seeds primed with brassinolide were significantly higher than those of the non-primed seeds under salinity stress in each variety. Seed priming with brassinolide significantly increased the shoot fresh weight, shoot dry weight, and root dry weight in 2 varieties, and significantly increased the root length and root vigour in each variety. It also significantly increased the activities of antioxidant enzymes, peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT), in Victoria and Victor seedlings. During seedling growth, the primed seeds significantly reduced the malondialdehyde (MDA) accumulation. This suggests that priming lucerne seed with brassinolide at a suitable concentration can improve germination and seedling growth under high-saline soils.

Association of polyamines in governing the chilling sensitivity of maize genotypes.

Chilling stress is an important constraint of global production of maize. This study was undertaken to compare the chilling responses of different maize seedling tissues and to analyze changes in polyamines as a result of chilling stress. Reponses to chilling were characterized in two maize (Zea mays L.) inbred lines, ‘HuangC’ and ‘Mo17’, that putatively differ in chilling sensitivity. Seedlings were exposed to low temperature (5°C) and chilling injury was estimated by electrical conductivity (EC), malonaldehyde (MDA) concentration, and by changes in putrescine (Put), spermidine (Spd) and spermine (Spm) concentrations in root, mesocotyl, and coleoptile tissues. Membrane permeability (as measured by EC), MDA concentrations and Put concentrations in the three tissue of maize seedlings increased after chilling stress, except for the Put concentration in roots. Spd and Spm concentrations in the three tissues of seedlings decreased after chilling stress. The EC for cold stressed tissues were lower in HuangC than Mo17. Also, the EC of coleoptile tissues were lower than for mesocotyl in both inbred lines. We suggest that mesocotyl tissue can be used to evaluate cold tolerance in maize. Stepwise regression analyses showed that chilling injury in roots was generally correlated with Spd concentration while in the mesocotyl injury was mainly correlated with Put and Spd concentrations. Spermidine and Spm concentrations in the coleoptile were correlated with chilling injury. Characteristics changes of polyamines in chill-tolerant maize seedling combined with regression analysis are a reliable method for evaluating chill tolerance in maize lines.

Alterations of seed variables under storage in nitrous oxide (N2O) atmospheres for two recalcitrant Quercus species

Abstract Storage of recalcitrant seeds was, and still is, problematic. This study investigated the effects of nitrous oxide (N2O) on storage of recalcitrant oak seeds. Containers of Quercus alba and Quercus macrocarpa seeds were placed under three atmospheric treatments: air, 80/20% and 98/2% of N2O/oxygen. Every 2 weeks (total of 12 weeks), a sample of five seeds was used to evaluate seed respiration in each atmosphere. Another set of five seeds was used to determine moisture content, seed, pericarp and embryo fresh weight, and embryo dry weight. Germination percentage was evaluated based on a total of 50 seeds for each treatment and each sampling time. Analysis revealed a treatment effect on seed fresh weight and moisture content, with increased values for N2O treatments. Quercus alba had greater respiration than Q. macrocarpa. The percentage of germination for Q. alba showed a consistent pattern, while for Q. macrocarpa it gradually increased. Storage time had an effect on the mean values for most of the seed variables.

Conditioning Shriveled Soybean Seed Part II. Correlation of Physiological Characteristics with Physical Properties

ABSTRACT The physiological properties of samples at different stages during conditioning of shrivelled soybean seedlots were analyzed and correlated with physical properties. Conditioning improved seed viability and vigor. Operation capacities needed to be reduced to obtain optimal separation of shrivelled seeds with minimal loss of good seeds. Correlations of shrivelled seeds with germination, cold, stress, oil and yield tests presented a negative trend. KEYWORDS. Soybean conditioning. Physiological properties.