Effects of Acclimatization Temperature on Activities of Antioxidative Enzymes in Mericlone of a Cymbidium Hybrid

Abstract

Mericlone plantets of Cymbidium Yamba 'Bayswater' transplanted in pots with sphagnum moss were acclimatized for 4 weeks at 15°C, 25°C and 35°C in growth cabinets illuminated at 50 μmol·m^-2·s^-1 during a 16-hr photoperiod. At 25°C, superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) activities of both leaf and root, except SOD activity of root and CAT activity of leaf, fluctuated slightly during acclimatization. The 35°C and 15°C treatments induced marked increases in activities of these enzymes within 48 hr after onset of the treatment. SOD activity of both leaf and root was the highest at the low temperature treatment, while that at 35°C was intermediate. Temperature of 15°C increased both APX and CAT activities of leaf, but had no effect on the enzyme activities of roots. Contrary to this, temperature of 35°C reduced APX and CAT activities of root which continued during the acclimatization; the effect was greater on roots than on leaves. These findings indicate that cymbidium seedlings are tolerant of low temperatures and that antioxidative enzymes may be appropriate indicators for acclimatization.