Effects of salt stress on ion accumulation and antioxidative enzyme activitiesof Oryza sativa L. and Echinochloa oryzicola Vasing

The effects of salt stress on physiological factors, such as inorganic ion absorption and antioxidative enzyme activities, of rice (Oryza sativa L. cv. Anapurua) and Echinochloa oryzicola Vasing were investigated. Although having similar morphology, rice arid E. oryzicola possessed considerably different salt-tolerance mechanisms. Echinochloa oryzicola was more salt-tolerant than rice. When exposed to salt stress (100 mmol L-1 sodium chloride, NaCl; sixdays), E. oryzicola had the ability to limit the accumulation of sodium ions (Na+), maintained high potassium ion (K+) content and had a constantly higher K+/Na+ ratio than rice. Rice was not effective in limiting Na+ absorption but had a higher antioxidative capacity than E. oryzicola. The constitutive activities of superoxide dismutase (SOD) and catalase of rice were three and five times higher than that ofE. oryzicola, respectively. Induced activities of SOD, ascorbate peroxidase and glutathione reductase were also higher in rice than in E. oryzicola. The high antioxidative capacity was one of the tolerance mechanisms used by rice to cope with salt stress. Therefore, the salt tolerant mechanisms are different between the two plants.