Effects of Cadmium Stress on Antioxidant Enzymes and Osmolyte Accumulation in Aromatic Rice Seedlings

Cadmium(Cd) has been proven to affect plant growth and development. Experiment was therefore, conducted to examine the influence of Cd on aromatic rice cultivars at tillering stage. The experiment was arranged in a randomized complete block design comprising three different aromatic rice cultivars (Meixiangzhan 2, Xiangyaxiangzhan and Guixiangzhan) and three Cd levels (0, 50 and 100 mg/kg -1 soil). Antioxidant enzymes (Superoxide dismutase (SOD), Peroxidase(POD), and Catalase(CAT)), osmolyte accumulation (proline, protein, total sugar, amino acid), lipid peroxidation (in terms of melanodialdehyde(MDA)) and growth parameters (plant height, and total dry matter content) and Cd uptake in rice cultivars exposed to different Cd levels were examined. The results showed that, with increased levels of soil Cd toxicity, activities of SOD and MDA contents increased, while activities of POD and CAT enzymes, as well as osmolyte accumulation and dry matter contents decreased for all cultivars. Cd uptake in roots and in shoots of all the cultivars increased with increased soil Cd contents. Uptake was higher in roots than in shoots with Meixiangzhan 2 showing the highest uptake in both roots and shoots followed by Xiangyaxiangzhan and Guixiangzhan cultivars. The results suggested that soil Cd toxicity have negative consequences on rice growth. Rice roots accumulated higher Cd than shoots and uptake varies amongst cultivars. Conclusively, Cd toxicity impaired early growth in rice by affecting physio-biochemical attributes, however, Guixiangzhan variety performed better than the other two varieties. Key Words; Cadmium effects, Rice, Uptake, Antioxidants Enzymes, Osmulyte accumulation