Floral Morphs, Pollen Viability, and Ploidy Level of Oxalis corymbosa DC. in Taiwan

紫花酢漿草在台灣的花柱型分布、花粉活性及染色體倍數之調查

蔡孟穎(Meng-Ying Tsai) ； 陳淑華(Su-Hwa Chen) ； 高文媛(Wen-Yuan Kao)

《Botanical Studies》 51卷1期 (2010/01) Pp. 81-88

摘要

紫花酢漿草(Oxalis corymbosa DC.)，在台灣爲外來種植物，在原生地（北美地區）具有花柱三型性（長花柱、中花柱和短花柱型）和結實等相關紀錄；引入台灣後，僅採用鱗莖行無性繁殖，並無結實之現象。本研究調查台灣紫花酢漿草族群之花柱型並觀察植株有無結實現象、測量花粉活性和染色體倍數，以探討其不結實的原因。在花柱型調查中，我們並沒有觀察到植株有結實的現象，也沒有發現長花柱型個體；中花柱型個體佔最大比率，且具黃色花藥，而短花柱型和半等高花柱型個體比率低且其花藥多呈現白色。進一步分析發現白色花藥花粉囊內並沒有花粉（完全雄不孕現象），而黃色花藥花粉囊內有活性的花粉比率很低，少於4%。經流測分析短花柱型和中花柱型個體之核DNA，發現兩者應具有相同染色體倍數。已知紫花酢漿草具自交不親和性且必須經由有效的授粉方式才能成功授粉，因此根據本研究結果推測，台灣目前缺少長花柱型個體、不同花柱型個體數量極端不等、且有活性的花粉比率很低，爲影響紫花酢漿草在台灣無法結實的重要原因。

關鍵字

流測分析 ； 花柱異型性 ； 雄不孕 ； 紫花酢漿草 ； 有性繁殖

並列摘要

Oxalis corymbosa, an exotic species in Taiwan, is a tristylous plant, i.e., with long-(LS), mid-(MS) and short-styled (SS) floral morphs, producing capsules in its native habitat. However, in Taiwan, this species was never observed producing fruits, and it reproduces vegetatively. In this study we investigated floral morphs, observed fruit and seed production of 23 populations, assessed pollen viability, and analyzed the ploidy level of some populations of O. corymbosa, in an effort to understand the factors limiting sexual reproduction of this species in Taiwan. No fruit or seed production were observed in any population. The study of morph proportions revealed that ratios of SS, MS, and semi-homostylous (SHS) individuals varied among the populations, and LS individuals appeared to be absent in this region. Furthermore, two types of anthers were observed, yellow anthers with pollen grains and white anthers without pollen grains. In each population, individuals with MS morph and bearing yellow anthers were dominant. SS and SHS individuals were less frequent than MS morph and almost always bore white and male-sterile anthers. The result of fluorochromatic reaction essay revealed that these populations had very low pollen viability (＜4%). Flow cytometry analysis of cell nuclei suggested that individuals with MS and SS floral morph had same ploidy level. These results indicate that absence of LS floral morphs, the unequal proportion of floral morphs, low pollen viability, and the presence of male sterile morphs may all contribute to the absence of sexual reproduction of O. corymbosa in Taiwan.

並列關鍵字

Flow cytometry ； Heterostyle ； Male-sterile ； Oxalis corymbosa ； Sexual reproduction