Exogenous Calcium Supplementation Improves Salinity Tolerance in BRRI Dhan28; a Salt-Susceptible High-Yielding Oryza Sativa Cultivar

Abstract

Salinity is one of the most brutal abiotic stressors, commencing a great stumbling block in the way of attaining food security in Bangladesh. Cultivation of rice in saline soils can be possible after enhancing its salt tolerance. This study aimed to examine the potential impact of exogenous calcium (3 and 5 mM Ca2+ in CaCl2) on conferring salt tolerance in rice (cv. BRRI dhan28). At the germination stage, Ca2+-primed seeds were grown under 100 mM NaCl stress conditions for nine days. At the seedling stage, rice seedlings were grown in a sandponic culture with Hoagland′s nutrient solution amended or not amended with 100 mM NaCl for 20 days with or without Ca2+ supplementation. Our results revealed that NaCl-stressed rice plants showed highly compromised germination indices and growth parameters, which could be attributed to reduced shoot and root growth, decreased photosynthetic pigments, increased H2O2 accumulation, and elevated levels of lipid peroxidation measured as malondialdehyde (MDA). On the other hand, exogenous Ca2+ application noticeably improved germination indices, growth and biomass-related parameters under salt stress. Ca2+-treated salt-stressed plants displayed amplified chlorophyll content, as well as suppressed the accumulation of H2O2, contributing to oxidative damage protection. Ca2+ supplementation for salt-stressed rice seedlings elevated relative water content without increasing excess proline, indicating the role of Ca2+ in maintaining water balance under stressful conditions. Furthermore, exogenous Ca2+ decreased membrane injury under NaCl stress, as mirrored by notably diminished levels of MDA in stressed seedlings. The defensive role of Ca2+ counter to oxidative stress was connected with the elevated activities of antioxidant enzymes such as catalase, ascorbate peroxidase, and peroxidase. In general, the best results in terms of growth at both germination and seedling stages were obtained in response to 3 mM Ca2+ treatment. Finally, Ca2+ supplementation can be an effective practice to cultivate rice in saline soils.