Arsenic accumulation and tolerance in rootless macrophyte Najas indica are mediated through antioxidants, amino acids and phytochelatins

Abstract

Arsenic (As) accumulation and tolerance response of a submerged rootless macrophyte Najas indica were evaluated during arsenate (AsV; 10–250μM) and arsenite (AsIII; 1–50μM) exposure. Higher As accumulation at AsIII exposure and more tolerance upon AsV exposure resulted in more toxicity during AsIII stress than AsV, which was evident through measurement of growth parameters and oxidative stress related parameters viz., lipid peroxidation (MDA content), electrical conductivity (EC) and hydrogen peroxide (H2O2) levels. Antioxidant enzymes and various amino acids were more prominent during moderate exposure of AsV, suggesting their possible role in As tolerance and detoxification. Various non-enzymatic antioxidant metabolites viz., ascorbic acid (ASC), glutathione (GSH), non-protein thiols (NPTs) and phytochelatins (PCs) biosynthesis involving phytochelatin synthase (PCS) activity increased more significantly during AsIII stress. However, PCs content seems inadequate in response to As accumulation leading to lower PC-SH:As molar ratio and higher As phytotoxicity during AsIII stress. N. indica may prove useful plant species for phytoremediation purpose in moderately As contaminated water bodies due to high As accumulation and tolerance potential.