朱蕉之花期調節、花粉發芽以及種子刻傷

Flowering Regulation, Pollen Germination, and Seed Scarification of Cordyline

朱蕉[Cordyline fruticosa (L.) A. Chev.]為熱帶與亞熱帶地區常見之重要盆栽與景觀植物；但臺灣欠缺自有品種，雜交授粉與種子發芽等技術仍不清楚。本研究分別於2012年4月、2013年9月、2019年10月與2020年4月噴施5000 mg·L-1 GA3於12個朱蕉品種植株心部葉片，包括錦葉朱蕉(‘Fire Fountain’)、大葉紅邊朱蕉(‘Plumdinger’)、亮葉朱蕉(‘Red Sister’)、白馬朱蕉(‘White Edge’)、暗紅朱蕉(‘Cooperi’)、紅白馬朱蕉(‘John Klass’)、艷紅朱蕉(‘Thelma’)、喀麥隆朱蕉(‘Cameroon’)、彩葉娃娃朱蕉(‘Cointreau’)、娃娃朱蕉(‘Dolly’)、巧克力朱蕉(‘Miss Andrea’)和月光朱蕉(‘Moonlight’)等。結果顯示於9-10月噴施可誘導植株於處理後8-14週開花。將冬季自然開花之白馬朱蕉與亮葉朱蕉花粉培養於添加0%-20%蔗糖之B&K培養基，結果以15%蔗糖處理之花粉發芽率較高。彩葉朱蕉(‘Tricolor’)開花當天之花粉發芽率可達100%，開花前、後一天之花粉幾乎不發芽。亮葉朱蕉自交後之花粉管延伸至花柱底端即停止，並未進入子房，顯示具配子體型自交不親和性。以砂紙磨破種皮可提高白馬朱蕉×錦葉朱蕉之雜交種子發芽率且縮短發芽天數。

Cordyline [Cordyline fruticosa (L.) A. Chev.] has been widely used as potted plants and for landscaping in subtropical and tropical areas. However, in Taiwan, almost all cultivars have been imported from overseas due to lack of information on flowering regulation, pollination technique, and seed propagation. A spray of 5000 mg·L-1 GA3 on leaves of 12 cultivars was conducted in April, 2012, September, 2013, October, 2019, and April, 2020, respectively. Results showed that flowering occurred 8-14 weeks after treatments in September and October for most cultivars, including ‘Fire Fountain’, ‘Plumdinger’, ‘Red Sister’, ‘White Edge’, ‘Cooperi’, ‘John Klass’, ‘Thelma’, ‘Cameroon’, ‘Cointreau’, ‘Dolly’, ‘Miss Andrea’, and ‘Moonlight’. The pollen of ‘Red Sister’ and ‘White Edge’ was collected from natural flowering plants in winter. The highest pollen germination rate was measured in 15% sucrose treatment when cultured in B&K medium with 0% to 20% sucrose. All pollen of ‘Tricolor’ germinated when collected at anthesis, whereas no pollen germinated one day before or after anthesis. Tissue section revealed that pollen germinated and pollen tubes reached the base of the style but not the ovary in self-pollinated flowers of ‘Red Sister’, indicating gametophytic incompatibility. Physical scarification increased germination rate and reduced germination time of hybrid seeds from ‘Fire Fountain’ crossed with ‘White Edge’.