Studies on wetting mechanism of plant leaves by rainfall.

1. 本研究旨在了解雨水对叶片表面结构和润湿性的影响。(1)对17种植物叶片的降雨润湿性进行了研究。在植物种类之间观察到相当大的差异。水稻、番茄、黄瓜、萝卜、菠菜等叶片表面水滴滞留量在10mg/cm^2以上，卷心菜、威尔士洋葱在5mg/cm^2以下。(2)成虫叶片的润湿性高于活性幼叶。(3)叶片表面蜡质与润湿性密切相关，受降雨影响显著降低。(4)降雨湿润3 d以上后离体植株叶片的干燥速率高于未湿叶片。(5)水滴在叶片上的接触角与叶片的润湿性密切相关。(6)叶片湿润可能与植物种类、叶龄、叶蜡、水滴接触角的差异有关。对Kurashiki的降雨pH值进行了4年（1988-1991）的测量。酸雨pH值低于5.6，在94%的总样本（208个降雨事件）中被观察到。黄沙从中国大陆飞来时，雨水pH值在7.0左右。

1. The studies were designed to obtain the information on the changes of structure and wettability of leaf surface by wetting of rain water.(1)Leaf wettability of 17 plant species by wetting of rainfall was examined. Considerable differences were observed among the plant species. Retention of water drops on leaf surface was 10mg/cm^2 or more in rice, tomato, cucumber, radish spinach, etc., and 5mg/cm^2 or less in cabage, welsh onion. (2)The wettability was higher in adult leaves than that of young active leaves. (3)The superficial waxes of leaves were closely related to the wettability, and decreased a markedly by the exposure of rainfall. (4)Leaves of various plants detached after wetting of rainfall for 3 days or more had a higher drying rate than that of non-wetted leaves. (5)The contact angles of water drops on leaves were closely related to the wettability of leaves. (6)The wetting of leaves may be attributed to differences in plant species, leaf age, leaf wax, contact angle of water drops.2. pH of rainfall at Kurashiki was measured for 4 years(1988-1991). Acid rain which had a pH value lower than 5.6, was observed on 94% of 'the total samples(208 rainfall events). When the yellow sand came fly from China continent, the pH values of rain water was 7.0 or so.