雨と植物反応に関する研究
(IX) インゲンマメの生長に対する降雨の期間と強度の影響
1987 年 42 巻 4 号 p. 319-327
詳細
1987 年 42 巻 4 号 p. 319-327
The effects of the duration and intensity of artificial rainfall (mist) treatment on the growth of the kidney bean plants were investigated. Seedlings of the plants were exposed to four levels of mist treatment (Precipitation: 1-5mm/h) in a growth chamber (20°C, artificial short-wave radiation was regulated at 2.8MJ/m2·day) for several days (1-5days). The growth and injury of plants were examined immediately after the mist treatments, and when the plants were kept at 20°C in a phytotron for 2 weeks when the mean natural short-wave radiation amounted to 9.4MJ/m2·day after the treatments.
1) The growth measured immediately after a 1- to 2-day exposure to mist showed hardly any influence from the different mist treatments. However, at the end of five-day exposure at the heavy mist treatments (2 and 5mm/h), the dry weight of the shoot and leaf area decreased in comparison with those at the light treatments (0 and 1mm/h mist): there was no significant difference between the 2 and 5mm/h mist treatments. The degree of wilting after misting increased with increases in the duration and intensity of the treatment.
2) With a misting duration of 1 day, the weight and leaf area of the plants grown in a phytotron for about 2 weeks after the mist treatment were larger than those of plants grown in the phytotron throughout the experimental periods, but were markedly smaller when the misting was continued for 3 days or more. The three-day exposure to 1mm/h mist had no effect on subsequent growth, but a 2 or 5mm/h mist reduced the subsequent growth in fresh weight, dry weight and leaf area: the differences in the growth between the two treatments were small.
3) The promotive effect of short-term exposure to the mist treatment on growth was mainly attributed to an effect of weak light during the treatment rather than an effect of shoot wetting. However, the inhibitory effect of long-term exposure to mist was attributed to both effects of weak light and shoot wetting by the mist treatment.
4) These results suggest that the effect of shoot wetting by rain on growth mainly depends on the duration rather than intensity (amount) of rainfall.
