Osmotic Adjustment of Natural Vegetation in Saline Soils

Abstract

Leaf samples of natural vegetation collected in selected areas of variable salinity (ECe - 4, 12, 22 and 36 dS m ) were assayed for different parameters viz.,  photosynthetic pigments, relative water content (RWC), nitrate reductase activity (NRA), proline, membrane injury index (MII) and ionic ratios to understand the osmoregulation mechanisms in plants. The results showed that the biochemical parameters like photosynthetic pigments, nitrate reductase activity and RWC followed a declining trend while, proline and MII increased with increase in salinity from 4 to 36 dS m^-1. The concentration of proline was maximum in P. oleracea at 36 dS m of conductivity while, it was least in C. sparsiflorus at 4 dSm^-1. The content of magnesium in leaves decreased whereas, potassium and calcium followed an increasing trend resulting in fall of Na⁺ /K⁺ ratio and rise in Ca²⁺ /Mg²⁺ ratio with increase in salinity. The correlations revealed that the electrical conductivity was positively and significantly correlated with proline, MII and Ca/Mg ratio, whereas it was negatively correlated with photosynthetic pigments, RWC, NR activity and Na/K ratio at 1% level of significance.