The effects of the impermeable seed coat characteristic in soybeans (Glycine max (L.) Merr.) on the seed's sponse to field environment, artificial drying, and storage potential were evaluated. Comparisons were made be. tween seed of ‘Dare’ and those of an experimental hardseeded line, D67‐5677‐1 which is similar to Dare in growth type and maturity. Hardseededness was beneficial in maintaining the viability of seed remaining in the field for up to 9 weeks after seed moisture initially declined to 20%. Resistance to moisture reabsorption by seed on unharvested plants of the hardseeded line was clearly superior to that of Dare, indicating a possible solution to seed viability problems encountered in areas where mature seed are exposed to extended periods of warm, humid weather. Drying hand harvested seed had no effect on viability but increased the number of hard seed. Seed from the hardseeded line displayed a substantially greater storage potential than those of the normal, Dare.

Low temperature condition during December to January can limit seed emergence and seedling establishment for peanut production in Thailand. The objective of this study was to determine the effects of peanut seed priming on seed germination and vigor under optimal and low temperature conditions before and after 9 months of storage. Tainan 9 peanut seeds were primed with salicylic acid (SA), ascorbate (ASA), CaCl2, or chitosan and tested for germination at 25°C (optimal temperature) and 15°C (low temperature) before and after a 9-month storage period. Seed priming with 50 mg·L−1 SA and 50 mg·L−1 ASA for 12 hours before germinating improved germination at 15°C when compared to untreated seeds both before and after 9-month storage. The high seed quality, illustrated by high germination percentage, high seed vigor, and low mean germination time related to the low autoxidation substrates: lipoxygenase (LOX), malondialdehyde (MDA), and high antioxidants: superoxide dismutase (SOD) and catalase (CAT). It suggests that peanut seed priming with salicylic acid and/or ascorbate can improve seedling emergence and growth under low temperature conditions.

Gibberellin (GA3) and brassinosteroid (EBL) interactions can stimulate germination, extend seedling growth and induce low temperature stress tolerance. The effects of GA3 and EBL on seed quality, α-amylase and total dehydro­genase activities of soya bean seeds at different vigour and temperature levels were studied. The results showed that medium vigour seeds dressed with 100 ppm GA3, 0.25 ppm EBL plus 50 ppm GA3, and 0.50 ppm EBL plus 100 ppm GA3 had significantly higher germination (GP) and seedling vigour rates (SVR) than those of untreated seeds. Similarly, 0.50 ppm EBL resulted in higher SVR of low and medium vigour seeds when compared to the control under low temperature. All soya bean seeds dressed with 100 ppm GA3 had higher GP, vigour, shoot and root lengths, and SVR under both temperatures than those of the untreated seeds, and mean germination time decreased. At 15°C, all seeds dressed with 0.50 ppm EBL plus 100 ppm GA3 had higher α-amylase activity than the untreated seeds, whereas seeds with low and medium seed vigour dressed with 100 ppm GA3 and 0.25 ppm EBL plus 50 ppm GA3 had higher total dehydrogenase activity than the untreated seeds.

Low temperature has negative effects on seed performance and seedling growth in soya bean, reducing stand establishment. It was hypothesised, that seed treatment with plant hormones could improve seed imbibition and performance at low temperature. Therefore, the effects of 24-epibrassinolide (EBL) and gibberellic acid (GA3) on soya bean seed germination were studied. Seeds of ‘CM60’ and ‘CM0701-24’ were imbibed with 0.25 or 0.50 ppm EBL, 50 or 100 ppm GA3, or distilled water at 10, 15, 20 and 25°C. The seed imbibition patterns of the two soya bean varieties followed a similar trend. Low temperature delayed seed imbibition resulting in longer time to reach the end of phases 1 and 2 of seed germination as compared with high temperature. Soya bean seeds treated with 50 or 100 ppm GA3 showed increased germination index, shoot and root length and reduced mean germination time. Thus, 50-100 ppm GA3 could be used as a pre-soaking seed treatment to improve soya bean seed and seedling performance under low temperature.