Studies on the Photosynthetic Activity in Several Kinds of Fruit Trees

II. Seasonal Changes in the Rate of Photosynthesis

Abstract

1. Photosynthetic activity was compared among several kinds of fruit trees and grape vines in relation to the development of leaf tissues. Seasonal change of photosynthetic activity was also examined.
2. The period from the sprouting to the commencement of apparent photosynthesis was shortest in peach and longest in satsuma mandarin trees. It was closely related to the rate of leaf tissue development. The developing rate of palisade and spongy parenchyma in the leaf tissue was earliest in the former and latest in the latter.
3. In each deciduous fruit tree and grape vine, the photosythetic activity was markedly increased during the period from the sprouting to the maturing stage of leaves. After a slight decrease in photosynthetic activity occurred in mid summer, an increasing trend was observed subsequently. It continued from late summer to early autumn and then the activity declined abruptly.
4. The photosynthetic activity of old satsuma leaves increased rapidly with rise in air temperature, and thus it became rather higher than that of spring cycle leaves. In July, however, there appeared a reverse trend of photosynthetic activity between current spring cycle and old leaves. Much the same situation as this continued until autumn.