Changes in antioxidant levels and activities of related enzymes in rice leaves exposed to ozone

Abstract

Changes in the levels of antioxidants such as ascorbate and glutathione and activities of related enzymes in rice leaves exposed to ozone at high or low concentrations were investigated. In rice plants (Oryza sativa L. cv. Koshihikari) exposed to ozone at a high concentration (0.50X 10 -6 m 3 m -3 (0.50 ppm)) for 8 h, L-ascorbate was oxidized while the content of oxidized glutathione (GSSG) increased without the concomitant decrease of the content of reduced glutathione (GSH). In addition, the activities of aseorbate peroxidase (AP), dehydroascorbate reductase (DHA reductase), and superoxide dismutase (SOD) declined, though the glutathione reduetase (GR) activity remained unchanged. A high concentration of ozone was considered to destroy the protection system against active oxygen species, resulting in the injury of the cell structure and functions. On the other hand, in the rice leaves exposed for 5 weeks to ozone at low concentrations (0.05• -~ and 0.10• the amount of Laseorbate and total ascorbate increased significantly by exposure to 0.05 X 10 -6 m 3 m -a O~ while the content of total glutathione (GSH+GSSG) decreased by exposure to 0.10Xl0 -6 m 3 m -30~. Activities of AP, GR, and SOD increased by the exposure to ozone at low concentrations. These reactions may be interpreted as protective responses to prevent or alleviate the damage of rice plants induced by ozone.

Effects of Ozone on Photosynthetic Components and Radical Scavenging System in Leaves of Rice (Oryza sativa L.)

“…The sensitivity of crops to O3 is influenced by the detoxification capacity of ROS in the leaves (Nouchi 1993;Bender et al 1994;Chernikova et al 2000;Cheng et al 2007). In the present study, the activities of radical scavenging enzymes such as APX, MDAR and GR in the leaves of both cultivars of rice were significantly increased by the exposure to O3 (Table 2).…”

“…The short-term effect of O3 on the photosynthetic components and radical scavenging systems of Japanese rice leaves were reported (Nouchi et al 1991;Nouchi 1993;Yoshida et al 1994a;Yoshida et al 1994b). However, no information concerning the long-term (chronic) effects of ambient levels of O3 on photosynthetic components and radical scavenging systems of Japanese rice leaves is available.…”

“…The glutathione pathway is catalyzed by dehydroascorbate reductase (DHAR) and glutathione reductase (GR). It has been reported that the levels of certain antioxidants and the activity of several radical scavenging enzymes in rice were increased by exposure to O3 (Nouchi 1993;Yoshida et al 1994a;Yoshida et al 1994b). However, the detoxification capacity depends on the concentration of O3, exposure period, age of plant tissues and genotype (Cheng et al 2007;Bender et al 1994).…”

“…The difference in the sensitivity to O3 among the cultivars of a crop might be related to the detoxification capacity for O3-induced oxidative damage in the leaves (Cheng et al 2007;Izuta et al 1999;Fuhrer and Booker 2003;Nouchi 1993). For example, Cheng et al (2007) reported that the detoxification capacity of O3-tolerant cultivar exceeded that of the O3-sensitive cultivar in soybean.…”

Evaluation of antioxidant properties of berries

“…However, the activity in other three berries ranges fi'om 0.7 -0.85 units/rag protein. In plants, antioxidant enzymes namely catalase (31) and peroxidase (32) have been shown to increase when subjected to stress conditions. The glutathione peroxidase was observed to be low in orange and gooseberry (424.48 -443.13 unitslmg protein), while the activity increased by two fold in tomato and four fold in grapes.…”