MITIGATION OF SALT STRESS IN TOMATO BY EXOGENOUS APPLICATION OF CALCIUM

Abstract

A pot experiment was conducted in the Horticulture Farm of Sher-e-Bangla Agricultural University, Dhaka, during the period from October 2013 to March 2014 to study the salt stress mitigation in tomato by exogenous application of calcium (Ca2+). The two factors experiment was laid out in Randomized Complete Block Design (RCBD) with four replications. Factor A is different levels of salinity induced by sodium (Na+) viz. 0, 2, 4, 6 and 8 dSm-1 and factor B is different concentration of Ca2+ viz. 0, 5, 10 mM. The total treatment combinations were 15 (5×3). The experimental results showed that salt stress significantly affects morphology, physiology, yield contributing characters and yield of tomato. Plant height, leaf number and branch number per plant were reduced with increased levels of salinity mostly at 6 and 8 dSm-1. Salinity also adversely affected the leaf and stem dry weight (gm), leaf area (cm2), leaf chlorophyll content, number of flower plant-1, number of dropped flower plant-1, number of fruit plant-1 and also fruit weight plant-1 mostly at 8 dSm-1. Salt treatment greatly increased the uptake of Na+ and decreased both potassium K+ and Ca2+ uptake in the leaves of tomato. Exogenous application of Ca2+ significantly mitigates the adverse effects of salinity on plant biomass production or morphology, physiology and yield. The plant height, leaf number plant-1, branch number plant-1, leaf area (cm2) plant-1, dry weight of shoot plant-1 (gm), leaf chlorophyll content as measured in SPAD value, the highest number of flower and fruit plant-1, fruit weight plant-1 were increased with the application of calcium than the control or without calcium. In addition, the uptake of Na+ decreased and uptake of Ca2+ and K+ increased in tomato shoot while plants were treated with Ca2+ under salt stress. The yield of tomato is gradually decreasing with the increasing levels of salinity. Interestingly, the rate of reduction of yield of tomato was decreased with Ca2+ in response to different saline conditions and the lowest yield was recorded at the highest salinity (8 dSm-1) along with without Ca2+. The present study also showed that the highest fruit yield recorded with without salt and 5 mM Ca2+ treatment combination which was statistically similar with control treatment combination. These results are consistent with the findings of regulation of ion uptake in presence or absence of Ca2+ at different levels of Na+ stress. Therefore, this experiment suggests that Ca2+ can effectively mitigate the deleterious effect of Na+ stress in tomato cultivation.