Study On Water Adaptation To Sweet Sorghum And Grain Sorghum

Arid and semi-arid regions account for approximately half of China's total land area. Global climate change and the concomitant localized droughts are likely to exacerbate water shortage in arid and semi arid areas. As fossil fuels grow increasingly scarce, people are looking for alternative energy sources such as biomass. Resistant to multiple stress factors such as drought and salinity, sweet sorghum is one of the most promising crops for bioethanol production. Sweet sorghum can be cultivated in agriculturally marginal and unusable land, thus avoiding the competition for farm areas with food crops. Recent studies show that moderate water deficit during certain growth stages tends to improve grain yield and quality, possibly due to compensation effects. The present study was carried out to investigate effects of drought stress and rewatering on sweet sorghum and grain sorghum during different growth stages. Potted LiaoTian1 (a sweet sorghum variety) and LiaoZa10 (a grain sorghum variety) seedlings were subjected to 3 different water treatment regimes. We measured leaf water content, chlorophyll content, concentrations of osmoregulation substances, activities of protective enzymes, and membrane lipid peroxidation.The results are as follows:During the seedling, jointing and filling- booting stages, leaf water content of sweet sorghum was consistently higher than that of grain sorghum. Chlorophyll content of both sorghum varieties was sensitive to drought stress during the jointing, booting, and filling stages. Seedlings were however rela Sweet sorghum and grain sorghum differed markedly in osmoregulation substance species. Sweet sorghum sweedlings relied on proline, soluble proteins, and potassium ion for osmotic balance, while grain sorghum sweedlings mostly used soluble sugars. During the jointing and booting stages, sweet sorghum continued to use proline, soluble protein, and potassium ion: grain sorghum switched to a mixture of soluble sugars and potassium ion; During the filling stage, both varieties mainly used proline for osmoregulation.During the seedling, jointing, and booting stages, sweet sorghum had relatively low MDA, indicating less membrane damage than grain sorghum. During the filling stage, however, sweet sorghum MDA levels were comparatively high. Neither variety showed high SOD and POD activities under drought stress.Sweet sorghum was more drought-resistant and productive than grain sorghum. Sweet sorghum also had stronger post-rewatering compensation effects.