‘糯米糍(73-S-20)’荔枝之種子發育與環刻促進著果

Seed Development and Fruit-Set Enhancement by Girdling in ‘No Mai Tsz (73-S-20)’ Litchi (Litchi chinensis Sonn.)

朱堉君(Yu-Jun Zhu)

指導教授 ： 林宗賢

共同指導教授 ： 張哲嘉 ； 楊雯如

國立臺灣大學/生物資源暨農學院/園藝學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.00082

摘要

‘糯米糍(73-S-20)’為優良荔枝品種，風味佳且具焦核特性，但有焦核率不穩且結實不良等栽培問題，故本研究調查其種子發育，探討焦核率變動之原因及促進著果之方法。

製作石蠟及徒手切片觀察種子發育，並依種子大小將果實分類為大核、小核及焦核果實，調查其果實性狀。焦核果實的單果重較大核果實低，但果肉重、及總可溶性固形物均無差異。‘糯米糍’種子發育早期，無胚種子比例高，然其果實會逐漸掉落，故隨花後天數增加無胚種子比例漸降；至花後63 天，種子達成熟期，正常種子、胚達子葉期、胚未達子葉期(胚敗育)及未觀察到胚的比例分別為11.5%、11.5%、34.6%及42.3%。未達子葉期的胚最後會褐化，但未能確定成熟果實中的無胚種子是否為早期敗育或是刺激性的單為結果所致。

進行人工授粉，調查與‘黑葉’花粉雜交對焦核率的影響，2007 及2008 年的開放授粉的焦核率為46.3%及80%，以人工授粉使‘糯米糍’自交的焦核率為38.4%及66.7%，但兩處理間差異不顯著；授‘黑葉’花粉的焦核率顯著降低至0%及30.2%。分別於‘黑葉’偏雌花、偏雄花及花期結束的同時，標定三批偏雌花正在開放之‘糯米糍’花序，其焦核率分別為99.6%、69%及50.9%。除雄、套袋，阻絕授粉可誘導'糯米糍’單為結果，著果率為9.2%，其胚珠不膨大，平均單果重及果肉重為4.2 g及2.9 g。人工授粉使‘黑葉’與‘糯米糍’雜交，會顯著降低焦核率；然開放授粉下，當黑葉花期結束後，亦有焦核率降低的情形，而‘糯米糍’與‘黑葉’偏雄花花期重疊，對焦核率的影響不顯著，顯示可能有‘黑葉’花粉以外的因素會影響焦核率變動。

利用盛花前環刻、疏花序及著果初期施用2,4-D，探討促進‘糯米糍’著果的方法。至果實發育中期，與對照組相較，環刻處理的新梢數增加率較低，且採收時的果穗形成率及單株產量較高；在焦核率較低的年份，環刻處理後，焦核率及總可溶性固形物也較對照組高。疏花序及施用2,4-D 無法顯著提高著果及果實品質。試驗結果顯示，盛花前環刻可促進‘糯米糍’荔枝著果，提高產量。

關鍵字

糯米糍荔枝 ； 焦核 ； 單為結果 ； 授粉 ； 環刻 ； 著果

並列摘要

‘No Mai Tsz (73-S-20)’ is an excellent shrivel-seed litchi cultivar, but with low yield and unstable propotion of shriveled seed. The object of this thesis was to study the seed development, the factors causing the variation of the percentage of shrivel seed, and tried to enhance the fruit set in ‘No Mai Tsz’.
Experiments were conducted in 2007 and 2008 to investigate the seed development in ‘No Mai Tsz’ litchi by paraffin- or hand-sectioning. Mature fruits were harvested and classified as normal-, small-, and shriveled-seed fruit based on the development condition of the seeds, and investigated the fruit characters and quality. The percentage of seed without any embryo growth was 90.9% initially but decreased gradually thereafter. However, most of embryos without cotyledon or aborted at the late stage of seed development. At 63 DAB (day after full bloom) the seeds became mature, the percentage of normal seed, seed with smaller cotyledon, seed without cotyledon outline and seed without any embryo were 11.5%, 11.5%, 34.6% and 42.3%, respectively. Those seeds without cotyledon outline became brown in color. It was uncertain that the seeds without any embryo were derived from stenospermocarpy or from parthenocarpy. The shriveled-seed fruits had less fruit weight than the normal-seed ones but their aril weight and total soluble-solid content were not significantly different.
The flowers of ‘No Mai Tsz’ litchi were pollinated manually by using the pollens of ‘No Mai Tsz’ or ‘Hak Ip’ varieties. The percentages of shriveled-seed from open pollination were 46.3% and 80% in 2007 amd 2008, respectively, and were significantly higher than 0% and 30.2%, respectively, derived from outcross. The percentages of shriveled-seed from selfcross were 38.4% and 66.7%, respectively, in 2007 and 2008 and were not significant different from those of outcross and open pollination. When the hermaphrodite function as female, hermaphrodite function as male of ‘Hak Ip’ bloomed sequentially in the orchard, the percentage of shriveled-seed derived from simultaneously open flowers in ‘No Mai Tsz’ were 99.6% and 69%, respectively, and 50.9% when flowers of ‘Hak Ip’ were not present. When the flowers of ‘No Mai Tsz’ were emasculated and bagged to prevent from pollination, 9.2% of flowers resulted in parthenocarpic fruits with fruit and aril weight of 4.2 gand 2.9 g, respectively, and without any economic value. These results suggested that pollination is essential for the development of aril and fruit to the economical size in ‘No Mai Tsz’ litchi. The relationship between pollination and the formation of shriveled-seed or seedless fruits are discussed. Outcross may decrease the percentage of shriveled-seed fruits but other unknown factors could not be excluded.
Girdling, flower-thinning and 2,4-D were tried in 2007 and 2008 to increase the yield and improve the fruit quality of ‘No Mai Tsz’ litchi. The rate of flushing of the girdled trees was higher than ungirdled ones up to the middle period of fruit growth. Also, the percentage of fruit-cluster formation and the yield of individual trees and the total soluble solid contents on girdled tree were higher than the ungirdled ones during the year with low percentage of shriveled seed. On the other hand, flower thinning and 2,4-D application did not enhance fruit set and fruit quality. These results suggested that girdling just before anthesis is beneficial for enhancing yield in ‘No Mai Tsz’ litchi.

並列關鍵字

‘No Mai Tsz’ litchi ； shriveled seed ； parthenocarpy ； pollination ； girdling ； fruit set

參考文獻

李雪如. 2004. 高雄區農技報導，玉荷包荔枝開花結果之促成技術. 行政院農委會高雄區農業改良場. 屏東. 台灣.

李雪如. 2006. 玉荷包荔枝開花及著果習性之研究. 高雄區農業改良場研究彙報 17:9-19.

曾玉霞、張祖亮、陳右人. 2005. 環刻對荔枝花芽分化的影響. 中國園藝 51:155-164.

黃弼臣、翁慎微. 1973. 荔枝授粉初步試驗. 中國園藝 19: 230-233.

農業統計年報. 2007. 行政院農業委員會編印. 台灣. 台北