Effects of double stress on antioxidant enzyme activity in Vigna radiata (L.) Wilczek

The effects of double stress environment i.e. lead (heavy metal) and NaCl (saline) on the activity of antioxidant enzymes in Vigna radiata seedling were studied. The antioxidant activities of enzymes, i.e of superoxide dismutase, catalase, ascorbate peroxidase, guaiacol peroxidase, glutathione reductase and their activity proportions were examined. Superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase and glutathione reductase activities were substantially increased in a combined stress environment as compared to catalase. Further, in comparison with catalase and ascorbate peroxidase, glutathione reductase showed increased activities together with superoxide dismutase in a combined stress environment. Superoxide dismutase and glutathione reductase showed higher activity proportion in combined treatment. Physiological role of these enzymes in stress tolerance mechanism is discussed. KeyWord: Antioxidant, catalase, enzyme activity, glutathione reductase, guaiacol peroxidase, scorbate peroxidase, seedling, stress, superoxide dismutase, Vigna radiata Abbreviations: APX – ascorbate peroxidase, CAT – catalase, GPX – guaiacol peroxidase, GR – glutathione reductase, ROS – reactive oxygen species, SOD – superoxide dismutase Introduction Environmental stress factors like drought, temperature, high salinity and heavy metals are the major constraint that limit plant growth and productivity, by disturbing the intracellular water balance. Usually, in fields or on agricultural land, unlike in a laboratory or even a greenhouse environment, plants are subjected to a manifold array of stress factor (SIDDIQUI et al. 2008, NAWAZ et al. 2010). However, most of the studies have been devoted to assess the physiological response of plants in a single stress environment like salinity (SINHA 1991, SHARMA and GILLS 1994, KUMAR and KUMAR 1996), drought (SHINOZAKI and YAMAGUCHI 2007) and heavy metals (HAMEED et al. 2000, JETLEY et al. 2004) and studies on the physiological responses of plants under a combination of such stresses are restricted to ACTA BOT. CROAT. 72 (1), 2013 145 * Corresponding address, e-mail: [email protected] Copyright 2013 by Acta Botanica Croatica, the Faculty of Science, University of Zagreb. All rights reserved. 611 Siddiqui.prn U:\ACTA BOTANICA\Acta-Botan 1-13\611 Siddiqui.vp 14. o ujak 2013 11:38:15 Color profile: Generic CMYK printer profile Composite 150 lpi at 45 degrees