Scavenging of reactive oxygen species in NaCl-stressed rice (Oryza sativa L.) - differential response in salt-tolerant and sensitive varieties

Salinity stress affects the metabolism of plant cells leading to severe crop damage and loss of productivity. Oxidative stress is one consequence of salinity that may be responsible for much of the damage. We investigated the immediate responses (enzymatic and non-enzymatic) to salinity-induced oxidative stress in two major rice (Oryza sativa L.) cultivars, salt sensitive Pusa Basmati 1 (PB) and salt-tolerant Pokkali (PK). Seedlings of both cultivars were subjected to NaCl stress (100-300 mM) for 42 h. Under NaCl stress, the salt-tolerant cv. PK showed higher activity of the ROS scavenging enzyme, catalase (CAT) and enhanced levels of antioxidants like ascorbate (ASC) and glutathione (GSH), than the sensitive cv. PB. Although superoxide dismutase (SOD) activity was lower in cv. PK, it showed lesser extent of membrane damage (lipid peroxidation) and lower levels of H2O2 than cv. PB under stress. The high levels of catalase activity indicate efficient scavenging of H2O2, which is produced more by non-enzymatic means than via SOD in cv. PK. These data indicate that concerted action of both enzymatic and non-enzymatic ROS scavenging machineries is vital to overcome salinity-induced oxidative stress in rice. (C) 2003 Elsevier Ireland Ltd. All rights reserved.