ANTIOXIDANT ENZYME ACTIVITIES AND PROLINE CONTENT IN MAIZE PLANTS UNDER PEG-INDUCED WATER STRESS

Drought is a stress factor with strong impact on crop productivity. A first plant response to drought is increasing production of reactive oxygen species (ROS). The imbalance between the production of ROS and antioxidants lead to changes in physiological and biochemical processes affecting plant growth and development. In order to limit oxidative damage under stress conditions plants have developed enzymatic and non enzymatic antioxidant systems which scavenge free radicals. Following improvement programs were created and selected new varieties and hybrids with performance characteristics such as drought tolerance. In this paper we have investigated the effect of water stress induced by PEG on antioxidant enzymes activities and proline content on 6 hybrid corn seedling stage, under laboratory conditions, compared to a control variant. Different levels of water stress were induced by using two concentrations of PEG 6000 (5% and 15%). There have been determined enzymatic activity of peroxidase, quality and quantity spectrum of isoperoxidase and proline content. Free proline content and enzymatic activity of total soluble peroxidase were determined spectrophotometric, isoperoxidase fractions were separated by electrophoresis in agarose gel, colorimetric identified and quantified by GelAnalyzer 2010 software. Obtained results show water stress induced changes in investigated enzymes activities and proline content (depending on the applied stress and the hybrid investigated). Stress level is positively correlated with indices analyzed at some hybrids and negatively correlated to others. Peroxidase activity increases compared to the variant control to all hybrids analyzed at the first level of stress (5% PEG) and shows a random variation in a 15% PEG accentuated stress. The application of water stress did not induce the biosynthesis of new isoforms but reveals variations in the enzymatic activity of isoperoxidase depending on the hybrid analyzed. It is observed that the protein content increases under the influence of stress applied to most hybrids investigated. The results lead to the conclusion that hybrids can tolerate analyzed water stress in the doses tested and recommended for selection KWS 2376 hybrid with high proline of 5% PEG and Danubian of 15% PEG.