Ionic Balance of Sugar Beet (Beta vulgaris L.) under Salinity Stress with Special Reference to Organic Acids and Antioxidant System

Sugar beet (Beta vulgaris L.) was subjected to salinity stress under pot culture condition. Seeds were germinated in pots, and after two leaf stage irrigated continuously as and when required with different concentrations of saline water (2 ds m⁻¹, 4 dsm⁻¹, 6 dsm⁻¹, 8 dsm⁻¹ and 10 dsm⁻¹), prepared by dilution of sea water. Leaf samples were collected after 9^th leaf stage (BBCH19) for measuring of lipid peroxidation and membrane stability index (MSI). Lipid peroxidation, measured as malondialdehyde (MDA) content and the membrane stability index (MSI) increased and decreased, respectively with increasing salinity stress. Salinity stimulation varied type of ion accumulation, where Na⁺ replaced K⁺ and Mg²⁺, Ca²⁺ contents decreased gradually as the salinity increased. Organic acid content also varied significantly among different treatments. In control, both oxalic and succinic acids were normally present in beet leaf but oxalic acid increased gradually over succinic acid under highest salinity stress. The SDS-PAGE protein profiling of the leaves revealed presence of low molecular weight (29 KDa to 18.4KDa) protein bands under high salinity stress.