椪柑之花期、果實生長及落果之觀察

OBSERVATION ON THE TIME OF FLOWERING, FRUIT DEVELOPING AND DROPPING OF PONKAN (Citrus poonensis, Tan.)

1.椪柑花期遲早及日數長短，深受當年氣溫之影響。台灣中南部花期為2-4月，期間約為30-90天。2.椪柑座果百分比，以盛花時期為最高，總座果率為26,5%。3.果實生長以花後一個月內最為快速，而後隨生長日數增多，逐漸隆低。果高與果寬月間生長差異，在花後至5月中旬，果高大於果寬，5月下旬至6月中旬二者之生長量大致相近，7月以後果寬生長量均大於果高，愈近果熟期愈為明顯。4.健全與病蟲果實生長比較，以健全果實為大，但季節生長量及成熟前果實大小，均未有顯著差異。遭受病蟲為害之果實，容易造成落果，局部被害或輕度受害，不足於影響果實整體發育。5.花期終後10-20天間為幼果脫落時期。到5月中旬截止，完成前期生理落果。生長期中之落果，健全果實在5月下旬及成熟前一月間較多。病蟲落果以6-7月最少。其餘月份落果率多寡不一，蓋與病蟲發生時期，噴藥防治是否得當有關。6.果實生長期間之落果率：蟲害落果率最高，為12%；次是病害，為10%；健全果僅有6%。

Ponkan is an important kind of citrus fruit of Taiwan. The acreage at present is estimated to be arrived 6,000 ha. throughout the island. It is partic­ularly suitable to the growing conditions of the Chianan arer. The increase of the acreage during the recent years may be due largely. to the government assistance in the improvement of cultural techniques and encouragement in the export of product. The purpose of this observation was to look into the basic nature of flowering, fruit deve loping and fruit dro_pping of ponkan during the growing season. The experiment was carried out at Chiayi Agricultural Experiment Station. The results thus obtained can be summarized as flowers: 1. The flowering peried of the ponkan ranged from February to April at the Central and Southern parts of Taiwan. The temperature was found to be related to the period of flowering, namely the higher the temperature, the earlier the flowering. Usually, the period of flowering lasted 30 to 90 days. 2. The highest rate of fruit setting occurred at the prime blooming. The percentage of. fruit setting was observed to be 26.5 96 of the total flowers. 3. It was observed that the rapid growth of fruit generally occurred right after the setting of fruits and it gradually slowe9, down from Mid-May up to the maturity of fruits. 4. The average size of healthy fruits was generally larger than that of fruits with certain damages, but the difference in monthly rate of growth failed to reach 5% level significance. Since the damaged fruits generally dropped off at the early stage of growth, the insignificance of the result may be due _primary to the dropping of damaged fruits. 5. The fruits were more or less subjected to physiological dropping at 10 to 20 days of the first month of the fruit growth. The rate of fruit dropping during the growing period was larger for damaged fruits when compared with that of the healthy ones. It was generally observed that the fruit dropping of healthy fruit mostly- occurred one month before maturity while that of damaged fruits dropped off sporadically during the entire period of fruit growth.