ウンシュウミカンの陽葉と陰葉のアスコルビン酸, 糖及びクロロフィル含量の季節変動とその成分相互間の関係

Abstract

The effect of differing light intensity on the diurnal and seasonal changes in ascorbic acid (AsA), sugar and chlorophyll contents in sun and shade leaves of 18-yr-old satsuma mandarin (Citrus unshiu Marc. cv. Hayashi) was investigated.1. AsA content in developing leaves in the exterior part of the foliar canopy increased during early May and decreased in June, 1989. The seasonal patterns of AsA content in sun and shade leaves were similar but their concentrations were different; that of shade leaves being consistently lower than that of sun leaves.2. 2-yr-old sun leaves contained higher AsA than shade leaves in July. AsA content of sun and shade leaves on clear day attained a maximum level during the day and decreased at night to the early morning level, but that on cloudy day was relatively higher at night than in the day. Patterns of fluctuations of sucrose in sun and shade leaves were similar to those of AsA content. High contents of AsA and sucrose of spring leaves were observed in sun leaves compared with shade leaves throughout the season. Levels of AsA and sucrose were low in mid-summer but they gradually increased until mid-winter, and then decreased abruptly as spring approached.3. In contrast to AsA and sugar contents, chlorophyll levels were higher in shade leaves than in sun leaves. Except for an initial rise in chlorophyll content of sun leaves on cloudy days in July, the trends generally tended to decrease from sunrise to midnight. Over the season, the maximum chlorophyll contents of sun and shade leaves were observed in January but there was no significant change.4. There were positive correlations between soluble sugars and AsA content, both diurnally and over the season. The coefficient of correlation between chlorophyll and AsA was significant but negative.