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Changes in antioxidant enzymes and polyamines in response to low temperatures in watermelon

Sung Whan Kwon , Bok Rai Ko, Sun Mi Huh , Dong Gye Bai

XXVIth International Societyof Horticultural Science Congres, Volume of Abstract . Toronto, Canada, 11-17 August, 2002. Abstract S11-P-95. pp. 317.

2002

บทคัดย่อ

Changes in Antioxidant Enzymes and Polyamines in Response to Low Temperatures in Watermelon

The changes in antioxidant enzymes and polyamines wree investigated in the leaves of watrmelon in response to a short exposure to chilling tempertures. Chilling temperatures not only reduced biomass and chlorophyll fluorescence but also caused an overall in crease of antioxidant enzyme activities and polyamines in the leaves of watermelon. After chilling treatment at 6 oC, the photochemical efficiency (Fv/Fm) of PS ll began to decrease slowly, and reached to 72.3% in 3 days as compared with 30 oC-grown plants. The antioxidant enzyme activitie after chilling treatment were higher in watermelon leaves with 30 oC-grown plants.The CAT and POD activities in leaves were significantly increased, reaching a maximum at 2 days after chilling treatment, while they was decreased slightly after 3 days. The means of antioxidant enzyme activities were higher to low temperatures in leaves than shoot apexes. In the native-gel assay of antioxidant enzymes, the treatment with low temperature resulted in quantitative changes in CAT and SOD isozyme profiles, while we can not found in qualitativ changes in these isozyme profiles, while we can not found in qualitative changes in these isozymes which were induced by chiling. In contrast, low temperatures induced the new synthesis of 3 POD band isozymes in watermelon leaves. Similarly increased polyamine contents of watermelon were found to be associated with antioxidant enzyme activities under the chilling conditions. Exposure to low temperature caused an incresse in SPD and SPM, but not in PUT levels. One of the possibility mechanisms of chilling resistance was observed to be due to the increased polymines against the marked increases in antioxidant enzyme activities. The results also indicate that SPD and SPM in watermelon leaves could have a protective role against chiling-induced active oxygen species.