International Journal of Farming and Allied Sciences Available online at www.ijfas.com ©2013 IJFAS Journal-2013-2-11/277-281 ISSN 2322-4134 ©2013 IJFAS Differential antioxidative response to drought stress and relationship with water use efficiency in maize hybrids Vahid Mozaffari, Hassan Pakniyat, Hojjat Hasheminasab and Hadi Pirasteh-Anosheh* Department of Crop Production and Plant Breeding, Shiraz University, Shiraz, Iran Corresponding author Email: Piraste@Shirazu.ac.ir ABSTRACT: Knowing about antioxidant enzymes activities after drought stress in plants are important, particularly in maize that is a sensitive plant to drought stress. Hence a study was conducted on six hybrids maize. Treatments were consisted of six maize hybrids: SC704, BC666, ZP599, SC524, ZP434, SC400 and irrigation at three regimes: optimal (100% FC), mild stress (75% FC) and severe stress (50% FC). Sampling was in stem elongation, tasseling and blisteringThe results showed that WUE slightly decreased under stress conditions, differences were non-significant. The activity of catalase and ascorbic peroxidase significantly increased while activity of peroxidase decreased under drought stress. Superoxide dismutase activity decreased and increased under mild and severe stress, respectively. According to These results suggest that superoxide dismutase is the best indicator for screening tolerance hybrids in drought stress and also stem elongation is the best stage. Keywords: drought, catalase, Superoxide dismutase, peroxidase, ascorbic peroxidase INTRODUCTION Maize (Zea mays L.), is an important crop in term of economical and forage, and is widely cultivated throughout the world. It is very sensitive to water stress during the growing season and water shortage is a challenge for maize production. Therefore it is urgent to understanding physiological mechanisms of maize under drought stress. Water use efficiency (WUE) is a key factor that determining plant production under limited water supply. In agronomic terms, it is defined as the ratio between total dry matter produced, or yield harvested and water used, or applied (Jones 1993). Yang et al. (2010) founds that drought tolerance is highly related to the plant antioxidant capacity and WUE. Plants respond to environmental stress such as water stress by altering their cellular metabolism and invoking various defense mechanisms. One of the defense mechanisms is the antioxidant detoxification system which consists of non-enzymes antioxidants e.g. glutathione and ascorbate, and antioxidant enzymes e.g. superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) (Foyer and Noctor 2000). When plants are subjected to environmental stress a variety of reactive oxygen species (ROS) are induced, such as superoxide anion radical (O 2 − ), hydrogen peroxide (H 2 O 2 ), hydroxyl radicals (OH) and singlet oxygen (O 2 ) (Jung 2004). The ROS may initiate destructive oxidative processes such as lipid peroxidation, protein oxidation, and damage to nucleic acids. Antioxidant enzymes are induced in plants to eliminate excess ROS. The activities of these antioxidant enzymes were altered when plants were subjected to stress. SOD functions as quencher to eliminate the radical of O 2 − thatformsH 2 O 2 . The function of CAT is to catalyze the degradation of H 2 O 2 to H 2 O directly. POD exists in all organelles of plants and catalyzes H 2 O 2 to oxidize ascorbic acid to generate H 2 O at the end of this progress (Foyer andNoctor2000). The effects of water stress on plant antioxidation have been widely studied. A number of researchers have reported antioxidants activity enhanced in drought stress (Ti-da et al. 2006; Fazeli et al. 2007). However other researchers have reported reduction in antioxidants activity in drought stress condition (Hu et al. 2010; Li-ping et al. 2006).Activities of antioxidant enzymes under drought stress would be extremely variable