Drought Essays -- Environment, Agricultural Field

Introduction: 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 (EC1.11.1.6) 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 )EC1.11.1.6( 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 ... ...ion of hydrogen superoxide hydrogen and peroxide occurs and causes disruptions in activity of some scavenger enzymes of reactive oxygen species like catalase in drought stress. This issue leads to increase of lipids peroxidation and finally damages chlorophyll and cell membrane. The plant to alleviate the adverse effects of oxidative stress caused by drought stress increases the activity of some involved enzymes in removing reactive oxygen species, like peroxidase, by stimulation of gene expression. This condition can be seen more in resistant lines. The stress-resistant lines having these traits reduce damaging effects of oxidative stress through degradation and inactivation of reactive oxygen species and because of more stability of cell membrane and chlorophyll under these conditions, access to high yield is probable due to sustaining photosynthetic capacity.