title: Differential responses of antioxidative defense system to prolonged salinity stress in salt-tolerant and salt-sensitive Indica rice (Oryza sativa L.) seedlings.
abstract: The present investigation evaluated the ability of an antioxidative defense system in terms of the tolerance against salinity-induced oxidative stress and also explored a possible relationship between the status of the components of an antioxidative defense system and the salt tolerance in Indica rice (Oryza sativa L.) genotypes. When the seedlings of a salt-sensitive cultivar was grown in sand cultures containing different NaCl concentrations (7 and 14 dS m(-1)) for 5-20 days, a substantial increase was observed in the rate of superoxide anion (O (2) (·-) ) production, elevated levels of H(2)O(2) and thiobarbituric acid reactive substances (TBARS) which indicated an enhancement in lipid peroxidation. A declination in the level of thiol clearly indicated an increase in the protein oxidation as well as a decline in the reduced forms of ascorbate (AsA) and glutathione (GSH) and the ratios of their reduced to oxidized forms occurred in the salt-sensitive seedlings. Similar treatment caused a very little alteration or no change in the levels of these components in the seedlings of salt-tolerant cultivar. The activity of antioxidative enzymes superoxide dismutase (SOD), its isoform Cu/Zn-SOD and ascorbate peroxidase (APX) increased in both the cultivars against salinity. In salt-sensitive seedlings, the activity of the various enzymes, guaiacol peroxidase (GPX), catalase (CAT), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) increased at moderate salinity treatment of 7 dS m(-1) NaCl while the activities of these enzymes declined with higher salinity level of 14 dS m(-1) NaCl. However, a consistent increase was observed in the activities of these enzymes of salt-tolerant seedlings with an increase in the duration and the level of the salinity treatment. The results suggest that a higher status of antioxidants (AsA and GSH) and a coordinated higher activity of the enzymes (SOD, CAT, GPX, APX, and GR) can serve as the major determinants in the model for depicting salt tolerance in Indica rice seedlings.
authors.affiliation: Department of Biochemistry, Faculty of Science, Banaras Hindu University, Varanasi 221005, India.
authors.forename: Pallavi
authors.initials: P
authors.lastname: Mishra
authors.forename: Kumari
authors.initials: K
authors.lastname: Bhoomika
authors.forename: R S
authors.initials: RS
authors.lastname: Dubey
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D012275:Oryza / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D018384:Oxidative Stress / Q000502:physiology; D054712:Salinity; D055049:Salt Tolerance; D055051:Salt-Tolerant Plants; D036226:Seedlings / Q000378:metabolism; D013312:Stress, Physiological / Q000502:physiology; D013481:Superoxides / Q000378:metabolism
chemical_list: D000975:Antioxidants; D013481:Superoxides