Changes in Concentration of Hydrogen Peroxide and Activities of Antioxidative Enzymes in Chilled Leaves of Acclimated Cattleya and Cymbidium Plants

Abstract

Naturally cold-acclimated (2 months from 10th Oct.) and non-acclimated (grown in a greenhouse at 13-28°C) potted plants of Sophrolaeliocattleya Estella Jewel (Cattleya) and Cymbidium Sazanami (Cymbidium) were exposed to 5°C for 24 hrs in the dark. Lower hydrogen peroxide concentrations were shown in plant leaves of cold-acclimated plants than in those of the non-acclimated ones during chilling treatment and during the daytime after that treatment. Superoxide dismutase (SOD) activities of cold-acclimated Cattleya leaves changed slightly at higher levels than those of non-acclimated ones during chilling treatment. Ascorbate peroxidase (APX) activities of the cold-acclimated leaves shifted to higher levels compared with non-acclimated leaves during and after cold treatment. The catalase (CAT) activities increased gradually in leaves that were cold-acclimated by chilling treatment, although those activities in non-acclimated leaves fluctuated markedly by chilling. SOD and APX activities of Cymbidium showed high values in cold-acclimated plants during chilling treatment. CAT activities in the cold-acclimated plants did not decrease temporarily like non-acclimated ones during chilling treatment, and decreased after the chilling treatment. From these results, it was indicated that cold-acclimation in autumn strengthened cold-resistance of both plant species in antioxidant relations.