Effect of Climatic Factors on Suction Force

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Abstract
The effects of climatic factors on the suction force of the leaf of Syringa oblata were studied, the soil moisture being kept in optimum condition. Among the climatic factors, air temp., light, relative humidity and evaporation were measured, rainfall and wind being neglected, as obviously less important under the conditions. In sampling only the horizontally disposed leaves were selected, thus eliminating the influence of exposure. Numerous (388) measurements were made. The suction force of the Syringa leaf shows a rhythmical diurnal fluctuation, caused by the fluctuation of climatic factors. Relative humidity is the most influential factor. The partial correlation coefficient is [long dash].469. Light exerts a very profound influence, only a little less than that of relative humidity. The influence of temp. is comparatively insignificant; the partial correlation coefficient is .165. The total effect of air temp., light intensity, and relative humidity on suction force is represented by a large multiple correlation coefficient which amounts to .812. The correlation coefficient of evaporation and the suction force is .828. It represents the total effect of all climatic factors, including both constant and intermittent factors. The relative importance of different climatic factors varies with the hr. of the day. At 6.30-10 a.m., both light and relative humidity exert strong influences but the the latter in a slightly higher degree. At 10 a.m.-2 p.m., relative humidity is the key factor, while the influence of light intensity is even less than that of temp. At 2-6 p.m., light intensity is the key factor; the influence of relative humidity is comparatively insignificant. At 6 p.m.-6.30 a.m., the effect of climatic factors on suction force is much less. The partial correlation coefficients of both air temp. and relative humidity are about 0.2. temp. remains an insignificant factor throughout the whole day.