Effects of Chilling on Antioxidative Enzymes in Leaves of Cattleya and Cymbidium

Abstract

Three foliar scavenging enzymes of reactive oxygen species : superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) in the CAM plant, Sophrolaeliocattleya Estella Jewel 'Kazumura' have low activities in comparison to those of a C3 plant, Cymbidium Sazanami 'Harunoumi'. The former underwent changes during chilling and cold-night acclimation which differed from those of the latter. 1. During exposure to 4°C for 24 hr in the dark, Cattleya leaves had lower SOD activities than had non-chilled leaves kept at 28°C, whereas their APX and CAT activities were higher. In chilled Cymbidium leaves, SOD and APX activities were significantly higher, whereas CAT was just slightly above those of non-chilled leaves. 2. In Cattleya leaves chilled for 8hr at 4°C for 10 days at night, SOD activities increased for 6 days and remained so until the last day, while APX activities increased for the last day. CAT activities increased for 2 days and then decreased gradually. In Cymbidium leaves, the SOD activity increased for 6 days, followed by a decrease ; APX activity, increased for 4 days, and subsequently remained at that level ; CAT activities increased for 2 to 4 days and then decreased sharply to a level below that of the non-chilled leaves. 3. Cold-night acclimation at 5°C for 40 days showed no significant changes in SOD activity between acclimated and non-acclimated leaves in both Cattleya and Cymbidium plants. APX activity in Cattleya increased gradually until the 30th day and that of Cymbidium increased for 20 days and then ceased increasing. CAT activity in Cattleya leaves was consistently and slightly higher during the acclimation period, while in the Cymbidium, it decreased for 20 days and, thereafter, recovered slightly.