Abstract
Propagated plants of a clone from "Du Puits" alfalfa were grown under two day-lengths ; short day--8hr natural daylight and long day--8hr natural light plus 8hr artificial light, and four temperature regimes; day 30°-night 25°, 25-20°, 20-15℃, and 15-10°, before or after cutting to observe the effects of these treatments on the regrowth process. 1) At the initial or first harvest when the pre-treatment was finished, the yield of herbage was greater at higher temperatures as the following order 25-20°>30-25°>20-15°>15-10℃. The yield of the second and third harvest, however, increased as the pretreatment temperature was lowered. Dry matter production of whole plant during the experiment period also increased with decrease of temperature. This seems to be caused by higher rate of photosynthesis based on greater total leaf area per plant resulting from higher rate of leaf expansion with a greater leaf size and darker green color in the plant pre-treated with lower temperatures. 2) Regarding with the effects of daylength and temperature during the regrowth period, the herbage production was greater under short day compared to that under long day, and the dry weight of roots increased with decrease of temperature and day length. Under long day and higher temperatures, the tops grew more, but under short day and lower temperatures, the roots grew more than the roots or the tops, respectively. The size of leaves formed after cutting, was greatest at 20-15° under long day and at 25-20° under short day, respectively, being decreased at higher or lower temperatures.
