葉片數與地面防雨覆蓋對愛文檬果花序形成之影響

Abstract

摘 要 臺灣地區7-10月為愛文檬果枝梢抽出、葉片發育時期，同時亦是颱風盛行季節，一旦有颱風侵襲檬果產區時，常導致檬果葉片大量掉落，影響該季的花序形成。因此本論文在探討葉片數與花序形成之相關性及田間鋪設Tyvek® 對花序形成時間的影響。所有參試的枝條都是抽過二次梢、完全成熟的枝條，以除葉及在離枝條頂芽30至40公分處環狀剝皮來控制葉片數。2003年12月27日處理的實驗顯示所有參試組別（留存20、 15、 10、 5及1片葉）翌年花序形成比率沒有顯著差異（皆高於75%）。考慮花序分化的時間點，2004年以10月9日、11月6日、11月20日與12月5日四個時間點進行處理（留存15、10、5及0片葉）。在留存0片葉中，11月20日前處理花序形成比率均為0%，其餘葉片數處理花序形成均為100%。在12月5日時，各種葉片數處理均可形成花序。2005年於10、11及12月中旬，各枝條分別留存10、5（二次梢）、5（一次梢）、3、1與0片葉，在玉井與枋山地區，除留存0片葉無法形成花序外，其餘葉片數處理有56-100％的花序形成比率。在芽體萌動後，隨葉片數減少，花序長度與品質有下降的趨勢。此外，在花序誘導期間枝條抽萌新梢，亦不利花序形成。連續三年的試驗結果顯示一片成熟的葉片足以誘導愛文檬果花序分化，不成熟的葉片則會抑制花序分化；花序品質與葉片數有關。在地面舖設Tyvek®畦面覆蓋層後，可降低土壤表面溫度，並減少地表溫度日變化的劇烈變動。減少樹冠外層的葉綠素含量及提高葉綠素a/b值，並降低玉井地區檬果的午間葉片水勢，但對於愛文檬果的光合作用能力、開花時間與形成比率並無顯著差異。

Abstract The shoot flushing and leaf development of ‘Irwin’ mango are occurred from July to October in Taiwan. During this period of time shoots are often suffered from typhoon attack, which lead to defoliation and thus resulted in a decrease of inflorescence formation percentage of that year. Therefore, the presented study was first to understand the relationship between leaf number and inflorescence formation in ‘Irwin’ mango, and then to evaluate the effect on inflorescence formation in ‘Irwin’ mango by modifying the microclimate in the field by Tyvek®, a rainproof ground coverage. All the shoots selected were fully matured and flushed twice, and leaf number was controlled by removing leaves and girdling at the position about 30 to 40 cm away from the shoot apex. Result of the first experiment on Dec. 27, 2003, indicated that all the treatment (20, 15, 10, 5, and 1 leaf retained) showed no significant difference in the percentage of inflorescence formation in the next spring (all > 75%). Considering the timing of floral initiation, four sets of similar experiment (15, 10, 5, and 0 leaf retained) were conducted in 2004 according to the timing of treatment; i.e. Oct. 9, Nov. 6, Nov. 20, and Dec. 5. On the leafless shoots, no any inflorescence formation was observed while treated before Nov. 20, whereas those of other treatments were 100%. All leaf-retaining treatments treated on Dec. 5 showed 100% inflorescence formation. In experiment of Oct., Nov., and mid-December in 2005, the leaf-retaining was 10, 5 (in second flush), 5 (in first flush), 3, 1, or 0 leaves conducted at two locations, Fang-Shan and Yu-Jing. In the treatments of retaining one or more leaves, the percentage of inflorescence formation was 56-100%; whereas, 0% of inflorescence formation was observed as no leaf retained. The length and quality of inflorescence tended to be decreased in decrement with leaf number. Moreover, shoot flushing closed to the timing of inflorescence initiation were disadvantageous to inflorescence formation. Upon the continuous three years’ study, the effect of leaf on inflorescence formation has been concluded that one matured leaf may sufficient for inflorescence initiation and the development and quality of inflorescence may depends on leaf number and shoot maturity. Covering furrow surface with Tyvek® could reduce the surface soil temperature and its diurnal fluctuation. A decrease of chlorophyll content and an increase of chlorophyll a/b ratio were observed in the leaves of the outward canopy. In Yu-Jing, Tyvek® also lowered the leaf water potential in the midday. However, Tyvek® had no effects on photosynthetic ability, blossom timing, and the percentage of inflorescence formation in ‘Irwin’ mango.