Secondary Pollen Presentation and Style Morphology in the Invasive Weed Mikania micrantha in South China

薇甘菊(Mikania micrantha H.B.K.)，又名小花蔓澤蘭，已在世界上很多地方成為一種成功的入侵雜草。我們從花的功能形態學，花柱在花期的生長和行為特徵，以及花柱的形態等方面，對薇甘菊的繁殖生物學進行了系統研究。本研究於2004和2005年的兩個薇甘菊花期選擇華南地區的一個開闊地中的薇甘菊種群進行。其中，薇甘菊的花生物學特性通過應用解剖鏡和掃描電子顯微鏡技術對不同發育階段的花進行觀測；柱頭可受性和花粉活力使用MTT[(3-(4,5-dimethylthiazol-yl)-2,5-diphenyl-2H-tetrazolium bromide)]染色技術確定。結果表明，薇甘菊的花為雄蕊先熟並具有菊科植物典型的次級花粉展現系統。薇甘菊的單花期一般為6天，我們根據花柱的形態和行為將單花的開放過程分為6個階段（A，B，C，D，E和F）。在開花的初始階段，花柱彎曲在花藥筒內，這種彎曲在花柱伸出過程中所產生的彈力可以幫助花柱突破由5個花藥形成的花藥筒，隨後花柱穿過花藥筒並將花粉從花粉囊帶出。MTT檢測實驗表明，薇甘菊花的雄性功能時期和雌性功能時期並沒有完全分開，仍有少量重疊：其中B-D階段為雄性功能時期，E為雌性功能時期。薇甘菊的花柱頂端具二叉分枝。掃粉毛位於花柱分枝的頂端和上部，起著展現花粉的作用。柱頭狀乳突細胞沿著每個花柱分枝在其腹側邊緣成二條帶狀對稱分佈。在開花初期，花柱的彎曲行為以及柱頭的掃粉毛在薇甘菊的傳粉過程中起著重要的作用。

關鍵字

入侵植物；薇甘菊；次級花粉展現；掃粉毛

並列摘要

Mikania micrantha H.B.K. is a successful invasive weed in many parts of the world. Its reproductive biology, specifically, floral functional morphology, growth and behavior of the style during anthesis, and style morphology, was studied in an open M. micrantha population in South China during the flowering seasons of 2004 and 2005. Floral biology was studied in detail by examining florets at different developmental stages under a dissecting microscope and a scanning electron microscope. Stigma receptivity and pollen viability was determined by MTT [3-(4,5-dimethylthiazol-yl)-2,5-diphenyl-2H-tetrazolium bromide] staining technique. The results show that M. micrantha is protandrous and has a secondary pollen presentation system which characterizes the family Asteraceae. Typically, the flowering period is 6 days and can be divided into six floral stages (A, B, C, D, E and F) based on style morphology and behaviour. At the beginning of anthesis, the style bends to break and enter the tube formed by five fused anthers. Later, the style protrudes the anther tube and moves the pollen out from the anther. During anthesis, two partially overlapping phases, functionally male phase and functionally female phase, can be distinguished by MTT tests: the former is from stage B to D, and the latter is stage E. The style has two style branches in its terminal part. The sweeping hairs, which act as pollen presenter, are located on the tips and on the upper parts of the style branches forming developed stylar appendages. The stigmatic papillae are separated into two ventro-marginal bands along each style branch in symmetric arrangement. The bending behavior of the style and the sweeping hairs play an important role in presenting pollen to pollinator.

並列關鍵字

Invasive plant ； Mikania micrantha ； Secondary pollen presentation ； Sweeping hairs

國際替代計量

Secondary Pollen Presentation and Style Morphology in the Invasive Weed Mikania micrantha in South China

全文下載

主題瀏覽