著者

矢野 義治

出版者

国立科学博物館

雑誌

筑波実験植物園研究報告 (ISSN:02893568)

巻号頁・発行日

vol.8, pp.37-44, 1989-12

---

The effect of soil moisture environment on the growth and development of plants was conducted from the transfer of water in the soil-plant-atmosphere continuum. The Japanese red pine (Pinus densiflora Sieb. et Zucc.), 7 years after transplantation in our botanical garden and the chinaberry tree (Melia azedarach L.) grown on a pot for 3 years were subjected to this test. The chinaberry tree is a species that experienced significant apparent water stress. Soil moisture was measured by a tensiometer and gravimetry, and sap flow velocity was measured by a heat pulse method. At the distances of 40cm and 80cm from the Japanese red pine, soil moisture was high, whereas at the distance of 120cm the moisture tension was low in the same as the moisture state of bare land where plant roots are absent. This phenomenon coincides with the root quantity distribution and seems to be caused by drying due to the absorption of soil moisture by a root. The sap flow velocity of the Japanese red pine changes gradually from 2cm/hr before sunrise to the maximum value of 20.6cm/hr at 12 o'clock and decreases in the afternoon to 2cm/hr two hour after sunset in correspondence with the amount of solar radiation. Daily changes of soil moisture and sap flow velocity in the chinaberry tree are quite similar to those in the Japanese red pine. When the drying of soil is advanced a soil moisture content ratio reached about 51%, sap flow velocity is lowered to 3cm/hr is spite of sufficient solar radiation. The deficiency of soil moisture causes wilting and obstructs the physiological functions of plant.