Transpiration of Evergreen Trees in Winter
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The results of my investigations may be briefly summarized as follows:- 1. The evergreen trees indigenous to Japan used in my experiments transpired in winter in Tokyo, an average quantity of, at least, 0.48 gr. Per □ dm. Per day (with the exception of conifers), or 16.58 gr. per 100 grams of fresh weight in foliage trees, and 8.18 gr. per 100 grams of fresh weight in foliage trees, and 8.18 gr. in conifers per day. 2. In the southern part of our country where the climate is milder (the mean temperature at Nagasaki in January being 5.℃.), the intensity of transpiration would undoubtedly be greater. But the contrary is no doubt the case in the northern part, especially in the island of Yezo, where the winter is severe (the mean temperature at Sapporo in January being -6.3℃.), and the plants must protect themselves from a great loss of water; and perhaps we may in their case expect the same occurrence of a minimum transpiration, as has been observed, for example, in Germany. 3. Not only is the transpiration continued in winter in Tokyo, but also the assimilation, as Miyake has recently shown, takes place without intermission in winter, though it is much feebler than in summer; and the non-cessation of these principal physiological functions in winter would naturally lead us to conclude that the abundance of evergreen trees in Japan is chiefly due to the favourable climate. 4. The time of minimum transpiration agrees with that of the minimum temperature, and occurs at the end of January. 5. The difference in the amount of transpiration in different species of evergreen trees becomes smallest at the time of minimum transpiration; and a change in the external conditions, especially in temperature, does not necessarily produce a corresponding change in transpiration in different species. 6. In average causes the amount of water transpired by foliage evergreen trees, is one and a half or two times greater than that transpired by conifers if we reduce the amount either to the fresh weight or to the dry weight of the transpiring part. 7. In diffused light at a temperature of ca. 10℃., the average transpiration of many evergreen trees amounts to 53 mgr. per □ dm. per hour. The present work was undertaken, at the suggestion of Prof. M. Miyoshi, during the academic year of 1898-1899, and, under his direction, I was able to carry on a large number of experiments. To both Prof. J. Matsumura and Prof. M. Miyoshi I wish to offer my heartiest thanks for their kind advice during the progress of my work in the laboratory of the Botanical Institute belonging to the College of Science. I am also indebted to Mr. K. Nakamura, Director of the Central Meteorological Observatory in Tokyo, for his kind permission to use the climatological tables made in the Observatory there, and to all other friends who have kindly assisted me in various ways.
- College of Science, Imperial University,東京帝國大學理學部の論文
- 1901-08-30
College of Science, Imperial University,東京帝國大學理學部 | 論文
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