MORPHOPHYSIOLOGICAL AND YIELD RESPONSES OF RICE PLANT (Oryza sativa L.) UNDER SALT STRESS AND MITIGATION BY CALCIUM

Abstract

A pot experiment was conducted in the Net House of Department of Agricultural Botany of Sher-e-Bangla Agricultural University, Dhaka, during the Boro season of (December-June) 2017-2018 to evaluate the response of BRRI dhan67 to calcium supplementation at different salinity levels. The two factors experiment was laid out in Completely Randomized Design (CRD) with three replications. Factor A is different levels of salinity induced by sodium (Na + ) viz. 0, 4, 6 and 8 dSm and factor B is different concentration of Ca 2+ viz. 0, 80, 160 ppm. The total treatment combinations were 12 (4×3). The experimental results showed that salt stress significantly affects morphology, physiology, yield contributing characters and yield of rice. Plant height and tiller number per plant were reduced with increased levels of salinity mostly at 6 and 8 dSm -1 . Salinity also adversely affected the leaf, root and shoot dry weight (gm), leaf area (cm 2 ), leaf chlorophyll content, leaf relative water content, leaf membrane stability, days to flowering, number of panicle plant , panicle length (cm), number of filled grains panicle -1 -1 , number of unfilled grains panicle , 1000-grain weight (g) and also grain yield g plant -1 . Exogenous

application of Ca 2+ mostly at 8 dSm significantly mitigates the adverse effects of salinity on plant biomass production or morphology, physiology and yield, leaf, root and shoot dry weight (g), leaf area (cm 2 ), leaf chlorophyll content, leaf relative water content, leaf membrane stability, number of panicle plant -1 , panicle length (cm), number of filled grains panicle -1 , number of unfilled grains panicle -1 , 1000-grain weight (g) and grain yield (g) plant -1 were increased and days required for flowering decreased with the application of calcium than the control or without calcium. The yield of rice is gradually decreasing with the increasing levels of salinity. Interestingly, the rate of reduction of yield of rice was decreased with Ca 2+ in response to different saline conditions and the lowest yield was recorded at the highest salinity (8 dSm ) along without Ca 2+ . The present study also showed that the highest yield recorded without salt and 160 ppm Ca 2+ treatment combination which was statistically dissimilar to control treatment combination in most of the cases. Application of both 80 and 160 ppm of calcium showed mitigating effect against salt stress but 160 ppm of calcium application showed better result than 80 ppm of calcium with or without salt (0, 4, 6, 8 dSm -1 level of salt) in every cases. These results are consistent with the findings of

regulation of ion uptake in presence or absence of Ca stress. Therefore, this experiment suggests that Ca 2+ 2+ -1 -1 -1 at different levels of Na can effectively mitigate the deleterious effect of Na + stress in rice cultivation and increase the potential salt stress tolerance in BRRI dhan67.