陳溪潭 呂俊堅 張明聰
The Leaf Dropping Habit in Matou Wentan (Citrus grandis)
Chen, H. T., C. J. Lu and M. T. Chang
This study is attempted to explore a micro-dripping irrigation system on the leaf-dropping of Matou Wentan trees. The system included a certain amount of water supply unit and a tension meter. Soil moisture included 20% (-8~-12 bars), 15% (-30~-40 bars) and 10% (-50~-70 bars), and a conventional orchard served as control. The results indicated that leaf-dropping occurred in the aging leaves and lamina dropped first in the daytime, which counted for 72% and mainly distributed in afternoon. The petiole dropped was found in the next few days both in the day and night times. Large portion of the lamina on the mother fruiting shoot dropped between February and March when trees were flushing and flowering. Less portion of leaf dropping was observed in the early flushing stage and then increased with time. First peak of the leaves dropped/day occurred in the late flushing stage, and the second peak appeared in the full flowering stage. Leaves of the Matou Wentan trees can remain on the shoots as long as 24 months and longevity of leaf distributed in every month. The longevity of leaf mainly distributed in the 11th~12th month of the flushing, the mainly distributed in 12~13th month when the spring flush delayed, and the next peak of distribution in the 21~24th month. Regardless of soil moisture, leaf-dropping occurred in lamina first and then petioles dropped after a few days later. Lowest leaf-dropping, i.e. 59.1%, in the daytime was observed in the treatment with 20% of soil moisture followed by 68.3% and 65.3%, with 15% and 10% of soil moisture, respectively. High leaf-dropping in a day occurred around 2 p.m. The remained leaves longer time on the shoots under high soil moisture. Not much of leaf-dropping was observed among the treatments in the winter season. Significant leaf-dropping started in April while flushing and flowering. Highest dropping, i.e., 74.4%, was observed in the treatment with 10% of soil moisture, followed by 56.6% and 41%, at the soil moisture at 15% and 20%, respectively.
Keywords: Matou Wentan, leaf drop, lamina, petiole, soil water content
Accepted for publication: June 24, 1997