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 (688KB)
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38,460,000 Yen (FY1999; 12,808,000 Yen)
The effects of increased UV-B radiation due to ozone layer depletion on the growth and yield of green and root vegetables in Brassica are investigated. Two hundreds thirty cultivars of cabbages, Chinese cabbages, and Japanese radishes were evaluated. UV-B was supplemented for several months until the harvest in 12 cultivars of cabbage, broccoli, cauliflower, and Japanese radishes and for about 2 - 4 weeks in the others. For UV-B supplement, automatic UV-B supplement apparatuses were placed in the field, and fluorescent sunlamps were adjusted so that the biological effect of UV-B in treatment plots is constantly twice that in control plots ( 4 times the value causing the estimated degree of ozone layer depletion in the middle latitude zone ) . Under these UV-B supplement conditions, no visible damage was observed in any cultivar. In the short-term UV-B supplement experiments, a total of 145 cultivars including those repeatedly examined were statistically analyzed. The dry matter increase significantly differed in 16 cultivars; being reduced in 13 cultivars but increased in the other 3. Though 14 of the 16 cultivars were repeatedly examined, none of them showed a significant difference of twice or more. Of the 12 cultivars in the long-term UV-B supplement experiments, 1 cauliflower cultivar showed a decrease in yield, and 1 broccoli cultivar showed an increase. Thus, the effects of increased UV-B radiation were not growth inhibition alone but sometimes growth promotion. Comparison of the effects of UV-B supplement on growth among cultivar groups revealed no marked differences. These results suggest that the effects of about 10% ozone layer depletion on the yield of vegetables are slight and can be ignored.
Ozone layer depletion, UV-B, Brassica. Growth, Yield