Floral Biology of Bidens Pilosa var. Radiata, an Invasive Plant in Taiwan

臺灣入侵植物大花咸豐草花部生物學之研究

黃雅倫(Ya-Lun Huang) ； 陳香君(Shiang-Jiuun Chen) ； 高文媛(Wen-Yuan Kao)

《Botanical Studies》 53卷4期 (2012/10) Pp. 501-507

摘要

外來植物入侵對全球生物多樣性造成嚴重的威脅。大花咸豐草被引入臺灣後，已成為嚴重的入侵植物之一。了解入侵植物的生殖生物學可以幫助我們有效控制其擴散。本研究主要在探討大花咸豐草的花部生物學，包含其（1）花部形態，（2）次級花粉呈現，（3）花粉／胚珠比。將採自嘉義的大花咸豐草種子種植在盆子中並放置於台大實驗農場；待植物開花後，觀察和分析其特徵。觀察發現大花咸豐草的一個頭狀花序上，有5-8個不孕的舌狀花和許多可孕的管狀花；除了觀察管狀花、花藥筒、花柱與花粉的形態，並定量一個頭狀花序上管狀花的數量、一個管狀花中花粉的數量與花粉／胚珠比；又根據花藥筒與花柱的形態將小花綻放過程分為六個階段，並分別檢驗這六個階段的花粉與柱頭活性。結果發現：一個頭狀花上管狀花的數量（19-61, 平均44.1）與一個管狀花所含花粉數量（6,556－11,378）在個體間有顯著差異。大花咸豐草的次級花粉呈現機制是由花柱伸長將花粉推出花藥筒。花粉與柱頭活性測定結果顯示，雖然雄性功能成熟期較雌性成熟期早，但兩者並未完全分開，故為不完全雄先熟。又根據花粉／胚珠比（8,827±464）的結果推測大花咸豐草的有性繁殖方式可能是完全異交。

關鍵字

自交 ； 大花咸豐草 ； 頭狀花序 ； 花粉/胚珠比 ； 雄先熟 ； 次級花粉呈現 ； 柱頭乳突 ； 掃粉毛 ； 異交

並列摘要

Invasion of exotic plants is threatening global biodiversity. Bidens pilosa L. var. radiata, a member of Asteraceae, has successfully invaded Taiwan after being introduced to the island. Knowledge of its reproduction is necessary in developing effective ways to control the spread of this plant. The objective of this study was to investigate the floral biology including: (1) floral structure, (2) the process of secondary pollen presentation, and (3) pollen/ovule ratio (P/O ratio) of this invasive plant. Plants were grown in pots from seeds and placed at the experimental farm of the National Taiwan University. Besides describing floral morphology, number of disk florets per capitulum, number of pollen grains per floret, and P/O ratio were quantified. Furthermore, we defined six floral stages according to anther tube and style morphology to investigate the process of pollen presentation and assessed pollen viability and stigma receptivity. Significant differences were found in the number of disk florets per capitulum (range 19-61, average 44.1) and the number of pollen grains in each floret (range 6,556-11,378) among individuals. Secondary pollen presentation was observed as the growing style brushes and pumps pollen grains out of the anther tube. Incomplete protandry was found from the observation of the flowering process and the tests of pollen viability and stigmatic receptivity. High P/O ratio (means ± s.e. : 8,827 ± 464) was measured which suggested that B. pilosa var. radiata might be obligately xenogamous.

並列關鍵字

Autogamy ； Bidens pilosa var. radiata ； Capitulum ； Pollen/ovule ratio (P/O ratio) ； Protandry ； Secondary pollen presentation ； Stigmatic papillae ； Sweeping hairs ； Xenogamy