抄録
It seems that the percentage yield of essential oil varies greatly according to climatic conditions. The fine weather during the harvest time seems to bring a good yield, whereas rainy or cluody weather lowers the yield. After a stormy weather, the yield becomes very poor. The experiments were undertaken from September to November in 1957 to determine the daily fluctuation of percentage yield of essential oil in P. roseum Willd. Results are shown in Fig. 1 and Table 1. The percentage fo essential oil is highest towards the evening but lowest in the early morning. The essential oil content of the leaves depends mainly upon weather conditions, ………the high temperature or the intensive sunshine greatly influences the yield of essential oil. When the temperature rises, the percentage yield of oil increases remarkably. But, in cloudy or rainy day, no marked daily fluctuation in oil content can be noticed. Moist conditions lowers the percentage yield of oil. The amount of water contained in the plant tissue is almost constant during the day time. It is concluded that daily fluctuation of percentage yield of essential oil must be caused by the change in the secretory activity of oil glands, because distribution of oil glands in the leaves is not changed.
