Arsenic-induced oxidative stress and thiol metabolism in two cultivars of rice and its possible reversal by phosphate

Abstract

Groundwater arsenic contamination, a grave threat in Bangladesh and parts of West Bengal (India), causes biochemical and physiological disorders in plants. Arsenic and phosphorus (plant macronutrient) have similar electronic configurations, resulting in their competitive interaction for the same uptake system in plant roots. Arsenic exposure initiates production of reactive oxygen species. Hence, the contents of proline, hydrogen peroxide, glutathione, ascorbate, and activities of ascorbate peroxidase, catalase were investigated in 21-day-old rice seedlings (cv. Khitish and cv. Nayanmani). Additionally, impact of arsenate together with phosphate on growth, total glutathione contents and activity of its regulatory enzymes were altered in the test cultivars to varying extents. Inductively coupled plasma-optical emission spectroscopic study of arsenic content in the root and shoot also showed variable uptake of arsenic by the two cultivars. Arsenate reductase enzyme activity primarily observed in the root, also differed from one cultivar to the other. Different phytochelatin (PCs) levels were recorded in the shoot and root of the cultivars under arsenate and phosphate treatment by reverse phase-high performance liquid chromatography. PC content increased with increasing arsenate concentrations, whereas phosphate and arsenate co-application resulted in reduced PC levels. The degree of elevation in PC contents varied significantly in the cultivars. Based on the above-mentioned parameters, cv. Khitish appeared to be more susceptible to arsenic toxicity than cv. Nayanmani which showed selective tolerance to the said metal stress.