Regulation of growth and metabolism in rice (Oryza sativa L.) by arsenic and its possible reversal by phosphate

The effect of arsenate with or without phosphate on the growth and metabolism in rice seedlings cv. MTU1010 was studied. In the test, cv. arsenic was more toxic for root growth, than for shoot growth, where root hairs were fewer and short, roots were characteristically stubby, brittle and root tips gradually turned brown. Arsenic caused damage to the root epidermal cells and aerenchymatous cortex. The level of total chlorophyll, chlorophyll-a, chlorophyll-b and fluorescence intensity were decreased in arsenic treated rice seedlings. Arsenic toxicity affected the activities of different antioxidant scavenging enzymes in the test seedlings. Activities of superoxide dismutase and ascorbic acid oxidase were increased, whereas catalase and catechol peroxidase activities were decreased by arsenic application. In these seedlings, the oxidative stress has been observed with arsenic treatments and the level of proline, H₂O₂ and malondialdehyde contents were increased. Joint application of phosphate with arsenic showed significant alterations on all parameters tested under the purview of arsenic treatment alone leading to better growth and metabolism in rice seedlings. Thus the use of phosphorus enriched fertilizers in arsenic contaminated soil may improve the production of healthy rice plants.