葉温と気温の測定に影響する要因について

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Temperatures of leaf cuttings of Ricinus communis L., and air temperatures are measured with a thermocouple (made of fine wire and copper-constantan) and a penrecorder (0.5mV range). 1. The use of a thermocouple is an effective method of measuring leaf temperature, for there is a remarkable difference of temperature between leaf surface and air at the same level. 2. There is little difference of temperature between the upper surface of a leaf and its lower surface, between its outer surface and its inner part, and between different points on its surface. 3. Leaf temperatures are a little lower than the surrpunding air temperatures in the weak light of 250 lux, but by far higher than the air temperatures in the strong light of 10,000 lux. Lowering degrees of leaf temperature in the wind given by a fan are larger than those of air temperature. 4. Leaf temperature is extremely higher than the temperature of the surface of both dry filter paper and wet filter paper under all the conditions mentioned above in 3. The temperature of the surface of wet filter paper is particularly low. These facts to a fall in temperature and that there is little effect of transpiration on the lowering of leaf temperature. 5. The fact that leaf temperature is higher in a violet leaf than in a white one shows that the absorption of radiation of light is related to the elevation of leaf temperature. 6. The air temperature at 1 mm above the leaf surface differs to a considerable degree from that at 15 mm or 110 mm above it, and is almost as high as the leaf temperature. From these facts it follows that the air temperature at 1 mm above the leaf surface directly affects the leaf temperature.

著者

宇佐美和夫
福岡女子大学家政学部

葉温と気温の測定に影響する要因について

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