Effect of salinity on gas exchange parameters and ionic relations in bael (Aegle marmelos Correa)

Abstract

Salt stressed bael cultivars showed marginal scorch, necrosis and abscission of leaves under both moderate (6.5 dS m-1) and high (10.7 dS m-1) salinity but control plants (1.3 dS m-1) did not exhibit these injury symptoms. While cvs NB-5 and CB-1 showed delayed onset and gradual progression of the stress symptoms, while NB-9 and CB-2 were worst affected and exhibited severe marginal scorch and necrosis in over 70% of the leaves in saline soils. At high salinity, NB-9 and CB-1 plants did not survive. Salt stress significantly (p≤0.05) reduced gas exchange and 6.5 dS m-1 salinity caused 28-32% decline in net photosynthesis and 29-39% reduction in transpiration rate in all cultivars relative to control. Although Na+ accumulation significantly increased in salt treated plants, cultivar NB-5 exhibited relatively similar distribution of Na+ ions in different plant parts and also maintained higher K+ concentrations in aerial parts. In spite of significantly high leaf Na+ (0.29%) at 6.5 dS m-1 salinity, cultivar NB-5 did not exhibit severe injury symptoms. Although CB-1 cultivar showed the tendency to retain Na+ ions in stem and root tissues, it failed to avoid the injury symptoms. Calcium was acquired in high amounts by salinized NB-5 plants as compared to others. Restricted Na+ uptake and preferential K+ accumulation seemed to contribute to alleviate the salt stress in cultivar NB-5.