Cold Stress on Some Selected Boro Rice Seedlings and Amelioration by Biochemical Approaches

Abstract

Cold stress is one of the critical environmental conditions that adversely affects crop growth and development resulting limit of yield and productivity. Field and Laboratory experiments were carried out three successive years to investigate the morpho-physiological functions of seedlings of eight rice varieties for cold survival mechanism during low temperature in Northwest Bangladesh and yield potential. The test rice cultivars from BRRI hybrid- BRRI hybrid dhan3 and BRRI hybrid dhan5, and HYV rice were BR 18 (Shahjalal), BRRI dhan28, BRRI dhan29 while indigenous cultivars were Lafaya, Biron dhan and Jagli. The root and shoot length, root and shoot weight, mean germination time, % survival or mortality, seedling vigor were recorded. Antioxidant enzyme activities like superoxide dismutase (SOD) and peroxidase (POD) were investigated at low temperature during study period. The leaf proline, chlorophyll, total carotenoid content was determined at ambient cold temperature and 6 °C in growth chamber during study period. Results indicated that low temperature and rice varieties had significant effect on the parameters studied while the salicylic acid positively improved the seedling growth and vigor. The superoxide dismutase (SOD) and peroxidase (POD) activities were increased in BRRI hybrid dhan5 at cold environment than those of other tested varieties. The BRRI hybrid dhan5 synthesized the highest amount of proline at 6 °C but the lower at ambient low temperature. The lowest amount of proline among the tested varieties was observed in cv. Lafaya at ambient low temperature and at 6 °C Similarly, the highest amount of chlorophyll-a was biosynthesized by BRRI hybrid dhan5 at ambient temperature but 6 °C while Salicylic acid application stimulated the chlorophyll. A significant variability was observed among the varieties regarding survival rate and mortality. The survival potentiality at low temperature environment during study period was observed as BRRI hybrid dhan5>BRRI hybrid dhan3>BRRI dhan28>Lafaya>Biron, respectively. The present finding infers that BRRI hybrid dhan5 showed the better survival potentiality than those of indigenous varieties during cold temperature by increasing anti-oxidant enzyme activities, higher synthesizing proline, and chlorophyll production resulted more biomass partitioning in root and shoot and increased seedling vigor index with low mortality that might inhibit cold injury due to occasional cold wave during Boro seedling raising time in winter and protect the seedling from adverse climate change effect. Salicylic acid application of 75 ppm, a biochemical approach that positively increased the seedling survival and improved the seedling growth during cold stress might be helpful for seedling raising in Northwest Bangladesh.