Analysis of arsenic induced physiological and biochemical responses in a medicinal plant, Withania somnifera.

Abstract

Withania somnifera has been an important herb in the Ayurvedic and indigenous medical systems for centuries in India. However, these grow as weeds mostly in the wastelands, which receive contaminated water from municipal and industrial sources. In the present investigation, plants of Withania somnifera were exposed to various concentrations of arsenate (AsV) and arsenite (AsIII) (0, 10, 25, 50, 100μM) for 10days and analysed for accumulation of arsenic (As) and physiological and biochemical changes. Plants showed more As accumulation upon exposure to AsIII (320μgg(-1) DW in roots and 161μgg(-1) DW in leaves) than to AsV (173μgg(-1) DW in roots and 100μgg(-1) DW in leaves) after 10days of treatment. Consequently, AsIII exposure caused more toxicity to plants as compared to that AsV, as evaluated in terms of the level of photosynthetic pigments and oxidative stress parameters (superoxide, hydrogen peroxide and lipid peroxidation), particularly at higher concentrations and on longer durations. Plants could tolerate low concentrations (variable for AsIII and AsV) until longer durations (10days) and high concentrations for shorter durations (1-5days) through increase in antioxidant enzymes and by augmented synthesis of thiols. In conclusion, As tolerance potential of Withania plants on one hand advocates its prospective use for remediation under proper supervision and on the other demonstrates possible threat of As entry into humans due to medicinal uses.