Effect of salinity and alkalinity on responses of halophytic grasses Sporobolus marginatus and Urochondra setulosa

Abstract

An experiment was conducted in micro-plots filled with sandy loam soil having 14% clay and 0.33% organic carbon to see the responses of halophytic grasses Sporobolus marginatus and Urochondra setulosa collected from the extreme saline-sodic Kachchh plains, Bhuj, Gujarat, India under alkalinity/salinity. Maximum photosynthetic rate was recorded in control treatment. Photosynthetic rate decreased at pH 9.0 + EC 20 dS/m (11.25 and 17.8 μmol CO₂/m²/s) in S. marginatus and U. setulosa respectively, along with reduction in stomatal conductance and transpiration rate. In comparison to control, increased accumulation of total soluble sugars and proline may be due to increased osmotic adjustment for both halophytes. Similarly, at mixed stress of pH 9.0 with EC 20 dS/m, the epicuticular wax load increased in both S. marginatus and U. setulosa (24.0 and 40.0 mg/g). A positive correlation of stress was seen with Na⁺ and Cl^‑ content while negative correlation with K⁺ content. Na⁺ content increased to about 3-7 fold at salinity level, EC 35 dS/m. Similarly, with treatment of mixed stress of pH 9.0 with saline level EC 20dS/m, 3-6 times increase in Na⁺ with decrease in K⁺ was observed in S. marginatus and U. setulosa respectively. These grass species maintained better gas exchange properties with higher osmolytes accumulations and balanced ionic relations under high stress conditions of salinity and alkalinity. These attributes might be providing physiological adaptable mechanisms for growth under salt affected environments.