Antioxidative Enzyme Response and Proline Biosynthesis in Two Cultivars of Indian Wild Rice under Hexavalent Chromium Stress

Chromium (Cr) is one of the most toxic heavy metal and is discharged into the environment through various anthropogenic and mining activities. Current investigation have made a comparative assessment on toxic impacts of varying doses of hexavalent chromium with respect to its antioxidative enzyme (Catalase and Guaiacol Peroxidase) response and proline accumulation in two cultivars (IC-283169 and IC-336684) of Indian wild rice (Oryza nivara) grown in hydroponics. Catalase activity showed significant gradual reduction with increasing treatment dose of Cr6+ in IC-283169 cultivar of O. nivara after 14 days of exposure period. A constant insignificant impact of Cr6+ up to the treatment concentration of 25 M was observed in IC-336684 cultivar of O. nivara. Catalase activity was highly stimulated showing a value of 20 kat g-1 fresh weights with the treatment of 50 M Cr6+ for 14 days of seedling growth. At an early stage of seedling growth i. e. for 7 days treatment, seedlings of IC-283169 cultivar of O. nivara showed high peroxidase activity (maximum at 75 M Cr6+ treatment) as compared to that of IC-336684 cultivar. After 14 days treatment, IC-336684 cultivar showed high peroxidase activity (maximum at 100M Cr6+ treatment). Proline content was maximum in IC-283169 cultivar of O. nivara after 14 days growth period at 100M Cr6+ treatment. Above results revealed the toxic impacts of Cr and plant response in respect to its free radical scavenging potentiality as an antioxidative protective system