Effect of thiourea application on root, old leaf and young leaf of two contrasting rice varieties (Oryza sativa L.) grown in arsenic contaminated soil

The present study was performed with two contrasting genotypes of rice, tolerant (Pooja) and moderately sensitive (CO-50), to evaluate their differential responses to arsenic (As, 50 mg kg(-1) soil) stress without or with thiourea (TU, 6.57 mM) application. The study analyzed tissue specific responses (root, old leaf; OL and young leaf; YL) of rice plants. TU was applied at different stages, viz., seed soaking and 25 days after sowing (DAS) and final harvesting was done at 45 DAS. Arsenic accumulation in Pooja roots (1067.94 mu g g(-1) dw), OL (131.67 mu g g(-1) dw) and YL (38.34 mu g g(-1) dw) was lower than that detected in CO-50 roots (4763.97 mu g g(-1) dw), OL (866.94 mu g g(-1) dw) and YL (334.08 mu g g(-1) dw) in As alone treatment. Arsenic stressed plants of both varieties showed reduced growth, decline in photosynthetic pigments and protein content. There was an increase in activity of antioxidant enzymes, SOD and GPX and total S in both varieties and root anatomical features were disturbed. Pooja showed lesser toxicity as compared to that of CO-50 in terms of various analyzed responses. The positive effects of TU on two varieties were visible as enhanced plant's growth in comparison to As alone treatment. The biochemical parameters showed a change in As+TU treatment so as to approach towards control value. The positive effect of TU was attributable to significant decline in As concentrations in both varieties. In conclusion, TU application can be a sustainable and feasible way to reduce As toxicity and accumulation in rice in field. (C) 2021 Elsevier B.V. All rights reserved.