Studies on wetting mechanism of plant leaves by rainfall.

(1)研究了17种植物叶片在雨水淋湿条件下的润湿性。不同植物种类间存在较大差异。水稻、番茄、黄瓜、萝卜、菠菜等作物叶表面水滴保留量均在10 mg/cm~2以上，小白菜、大葱叶表面水滴保持率均在5 mg/cm~2以下。(2)成叶的润湿性高于幼叶。(3)叶片表面蜡质与润湿性密切相关，降雨量显著降低叶片表面蜡质含量。(4)不同植物在降雨湿润3d或以上后脱落的叶片的干燥速率高于未湿润的叶片。(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、水滴接触角不同有关。连续4年(1988-1991年)对仓城县的降水进行了PH值测量。酸雨的出现占总样本(208次降雨)的94%，当黄沙从中国大陆飞来时，雨水的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.