本試驗調查台南地區黑葉荔枝品種（Litchi chinensis Sonn cv. Haak Yip），連續間歇性抽梢行為，及觀察低溫來臨時頂端芽體或枝梢，生長狀況與抽穗率及花穗形態的關係。1992年6月中旬自果實採收後，至當年12月底之抽梢情形為；原來就有結果的枝條，在採果後萌發一、二與三次梢比例依序為35、55與10％，萌發枝梢在翌年抽穗率依序為71、76與0％。原來並無結果的枝條，在6月中旬後再萌發一、二與三次梢比例依序為20、45與0％，未再萌發者佔35％；未再萌發枝梢翌年抽穗率為90％，再萌發一與二次梢者抽穗率依序為85與16％。無論原來是否結果，在連續間歇性抽梢過程中，最一次梢萌發期在7、8月者，其翌年抽穗率均較在10月以後萌發者為高。因此，荔枝花穗形成與否，與連續間歇性抽梢最後一次抽梢期較有密切關係。1990年及1991年冬季低溫期，調查最後一次梢頂芽或枝梢，因長度之不同而影響次年抽穗率；頂芽長度0.2 cm者次年枝梢抽穗率為零。頂芽長度0.3∼0.5 cm時次年枝梢抽穗率為60％，其花穗為無葉花穗。頂芽長度0.6∼2 cm時芽體充實飽滿，枝梢抽穗率達90％以上，其花穗為無葉花穗。頂芽長度2∼5 cm時枝梢抽穗率為55∼80％，其花穗易形成帶葉花穗。枝梢長度5∼9 cm時新梢小葉片易受低溫寒害而落葉，次年在其落葉枝頂芽或腋芽抽穗，其枝梢抽穗率為25∼85％。枝梢長度10 cm以上之紅葉新梢，低溫期間葉片繼續生長，次年枝梢抽穗率為零。因此荔枝植株於10∼11月間，在低溫未來臨前，抑制芽體長度在0.6∼2 cm，或枝梢已抽生在10 cm左右時除葉，可抑制植株抽梢，提高抽穗率，防止植株隔年結果，穩定產量。
Studies on the Flush Growth and Panicle Formation of Litchi
Chern, S. T.
Experiments were conducted to investigate the discontinuous growth of flushing of litchi (Litchi chinensis cv. Haak Yip) in Tainan area and to observe the relationships between the growth of flush and percentage of panicle formation/type as they were growing under the condition of discontinuous cold streams. From June after harvesting to December 1992, 35,55 and 10% of the fruited twigs were found with once, twice or thrice of flushings after harvesting, respectively, and their flowering percentage in the following year were 71, 76 and 10%. For the un-fruitted twigs, 20, 45 and 0% of the twigs were found with once, twice and thrice of flushings, respectively, after harvesting and 35% remained un-flushed. Ninety percent of the un-flushed twigs were found with flower panicles in the following year. For those twigs with once or twice of flusings, the percentage of panicle formations were 85 and 16%, respectively. Whether the twigs were fruited or not, if the flushings occurred in July or August, they were found with higher percentage of panicle formation than that flushed in October. Therefore, panicle formation of litchi is highly correlated to the time of last flushing in the previous year. Results of the winter between late 1990 and early 1991 revealed that panicle formation also affected by flush length. If the flush was less the 0.2 cm, no panicle will be produced in the next year. Sixty % of the 0.3~0.5 flushes were found with panicle formation and they were all leafless panicles. Ninety % of the 0.6~2.0 cm flushed were found with leafless panicles. Fifty-five to 80% of the 2~5 cm flushes were found with leafy panicles. If the flushes were longer than 5~9 cm, the delicate small young leaves were easily be chilled and defoliated by the cold streams but 25~85% of the defoliated flushes were also found with panicles produced from the top of axillary’s buds. If the flushes were longer than 10 cm, the leaves were continuous to grow in the winter and no panicle was observed in the next year. For the best panicle formation of litchi, the length of flush should be controlled within 0.6~2 cm in October to November. If the flushes were longer than 10 cm, the leaves should be removed. Then percentage of panicle formation increased. This practice prevent litchi from alternate fruit setting and stabilize the yield of litchi fruits.
Key words: litchi, shoot, flower
Accepted for publication: July 5, 1994.