Drought is the most significant factor restricting plant production on majority of agricultural field of the world (Tas&Tas, 2007). During drought stress, improper adjustment of photosystem II and thermodynamic damages disrupt the flow of electrons and lead to production of free radicals. Oxidative damages results from incomplete detoxification of reactive oxygen species. Damages caused by oxidative stress includes; inactivation of enzymes, lipid peroxidation, protein degradation and destruction of DNA strands, reduction in chlorophyll content and pigments color (Friso et al., 2004, Gechev et al., 2006; Baruah et al., 2009). Detoxification of reactive oxygen species in plants, includes enzymatic mechanisms (such as superoxide dismutase (SOD), catalse (CAT), ascorbate peroxidase (APX), peroxidase (POX), glutathione reductase (GR) and mono dehydro ascorbate reductase (MDAR) as well as non-enzymatic mechanisms (such as flavonoids, anthocyanins, carotenoids and ascorbic acid, AA) (Friso et al., 2004, Ramachandra Reddi et al., 2004). In enzymatic antioxidant systems, catalase (EC220.127.116.11) is an oxidoreductase located in peroxysomes and considered as an important enzyme to counter hydrogen peroxide produced in stress conditions so that at drought stress conditions new isomorphs of it are released and the rate of former isomorphs increases (Srivalli et al, 2003 and Khana-chopra and Selote, 2007). Peroxidase )EC18.104.22.168( as another enzymatic antioxidant systems, is an oxidoreductase that has one homogeneous –b as a prostatic group and catalysis oxidation of the proton giver compounds with H2O2 and consequently cause H2O2 to breakdown (Jiang and Zhang, 2004). In most studies under drought condition increase in activity of this enzyme was reported (Srivalli et al., 2003, Jiang and Zhang, 2004). This research conducted to study the effect of drought stress on activity of some antioxidant enzymes and to measure the role of these enzymes in decreasing oxidative stress damages in chlorophyll and cell membrane due to drought in sensitive and resistant lines of wheat.
Methods and Materials:
In this study, seven wheat lines including tolerant lines (Unknown 11, Homa and Ohadi), semi-tolerant lines (Sabalan , Rasad ) and sensitive lines (SARA-PBWYT-85-86-22-5 and SHARK-4-0YC-0YC-0YC-5YC-0YC) were evaluated in a factorial experiment based on randomized complete blocks with three replicates in rain-fed condition at Marageh Agricultural Research Station (2009-2010). The seeds were sown on 22 November 2009, in 5 rows 20 cm apart with the density of 200 seeds m–2. The needed nitrogen for wheat based on field experiment results was 60 kg net nitrogen per hectare from urea source added to the soil in fall (Feyziasl & Valizadeh, 2003, Feyziasl & Valizadeh, 2001). The needed phosphorous was supplied on the basis of soil test and phosphorous deficit from critical level in soil (9 milligram per hectare) (Feyziasl et al, 2004). Irrigation of...