John Wiley & Sons, Ltd.

Arsenite stress variably stimulates pro‐oxidant enzymes, anatomical deformities, photosynthetic pigment reduction and antioxidants in arsenic tolerant and sensitive rice seedlings

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Contamination of arsenic (As) in rice (Oryza sativa L.) paddies and subsequent uptake by rice plants is a serious concern as rice is the staple crop for millions. Identification of As toxicity and detoxification mechanisms in paddy rice cultivars would help to reduce As‐associated risk. Arsenic tolerance and susceptibility mechanisms were investigated in two differential As accumulating rice genotypes viz., Triguna and IET‐4786, selected from initial screening of 52 rice cultivars as an As tolerant and an As sensitive cultivar respectively, on the basis of root and shoot length during various arsenite (AsIII) exposures (0‐50 µM). Indicators of oxidative stress such as pro‐oxidant enzymes (NADPH oxidase and ascorbate oxidase) and nitric oxide were more numerous in sensitive cultivar than the tolerant cultivar. Arsenic‐induced anatomical deformities were frequent in the sensitive cultivar, showing more distorted and flaccid root cells than the tolerant cultivar. Chlorophyll and carotenoid synthesis were inhibited in both cultivars, although the decline was more prominent in sensitive cultivar at higher doses of As. However, tolerant cultivar tolerated As stress by producing more antioxidants such as proline, sustaining the ratio of ascorbate, dehydroascorbate and glutathione peroxidase (GPx) activity as well as As detoxifying enzymes arsenate reductase (AR), whereas these respective metabolic activities declined in sensitive cultivar, resulting in greater susceptibility to As toxicity. This article is protected by copyright. All rights reserved

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