限制紫花酢漿草在台灣的分佈及其有性繁殖之因素探討

Studies on factors limiting the distribution and sexual reproduction of Oxalis corymbosa DC. in Taiwan

蔡孟穎(Meng-Ying Tsai)

指導教授 ： 高文媛

國立臺灣大學/生命科學院/生態學與演化生物學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.01354

摘要

紫花酢漿草（Oxalis corymbosa DC.），在台灣為外來種植物，春季多茂盛生長於公園綠地以及荒廢地，夏季僅在較陰暗的環境才能發現其蹤跡，此外，北部比南部具有較多的紫花酢漿草族群；又其在原生地有結實紀錄，引入台灣後，採用鱗莖行無性繁殖，並無結實之現象。本研究目的有二，目的一：比較紫花酢漿草族群在不同光度和水分處理下的反應，以探討主要限制其生長在上述棲地的原因；目的二：調查花柱型、測量花粉活性、染色體倍數，以探討其不結實的原因。實驗結果發現，春天時在不同光度處理下的植株，其生物量和光合作用參數都無顯著差異。而在夏季高光度、澆水處理下，全光照組的生物量高於遮光處理組；但在高溫、強光下，紫花酢漿草有明顯光抑制現象。而在春季進行乾旱處理下，紫花酢漿草的光飽和淨光合作用速率、生物量等都顯著降低。因此推測水分才是主要限制紫花酢漿草分佈的重要因素。紫花酢漿草在原生地有花柱三型性，於2005-2007年間隨機調查台灣本島的紫花酢漿草族群，並沒有發現長花柱個體，中花柱型個體佔最大比率且其花藥多呈現黃色，而短花柱型個體比率低且其花藥多呈現白色。黃色花藥花粉囊內有活性的花粉比率很低，約4%花粉有活性，而白色花藥花粉囊內不具有花粉。比較台灣紫花酢漿草各花柱型的核DNA含量，發現其具相同染色體倍數。因此，白色花藥不產生花粉，並非染色體倍數異常所造成。觀察埋蠟切片，發現白色花藥有發育不正常的營養層。經由溫室以及生長箱實驗，發現溫度和光度會影響上輪雄蕊花粉的活性；適當的溫度和光度雖然可以提高紫花酢漿草上輪雄蕊花粉活性，但因台灣並沒有長花柱個體，將無助於提高其成功授粉機率。紫花酢漿草因具有自交不親和性且必須經由有效的授粉方式（legitimate pollination）才能成功授粉；推測台灣目前缺少長型花柱個體且花粉活性過低，為影響紫花酢漿草無法結實的重要原因。

關鍵字

紫花酢漿草 ； 光度 ； 水分 ； 有性繁殖 ； 花粉活性

並列摘要

Oxalis corymbosa is an exotic plant in Taiwan. In spring, O. corymbosa thrives in parks and wastelands, but is found only in shady environment during summer season. In addition, O. corymbosa has more populations in northern than in southern Taiwan. Though O. corymbosa has been observed producing capsules in its native habitat, it has no fruit in Taiwan and uses vegetative reproduction by bulbs. There are two objectives of this study: first, to examine the response of O. corymbosa under different irradiance (PAR) and watering regimes; secondly, to study factors limiting seed-set of O. corymbosa in Taiwan. Results showed that plants under two different light treatments in spring had no significant difference in biomass and photosynthetic parameters. But plants of O. corymbosa grown under full light and well water condition in summer had greater biomass than those in shade. Under high light and high temperature condition, leaves of O. corymbosa suffered obvious photoinhibition. Grown under drought treatment, O. corymbosa had significant reduction in light-saturated net photosynthetic rate and biomass. These results suggest that low soil moisture may be an important factor restricting the growth and distribution of O. corymbosa. The flowers of O. corymbosa have tristyly in its native environment. To investigate flower morph, I surveyed O. corymbosa populations in Taiwan during 2005-2007. Long morph individuals were not found, and mid morph individuals (96.7%) were found to have the greatest proportion in Taiwan. In addition, most of short morph individuals had white and sterile anthers. However, the percentage of vital pollen of O. corymbosa (~4.0%) was much lower than that of O. corniculata (~54.9%, the native congener of O. corymbosa in Taiwan). The analysis of nuclear DNA content revealed that O. corymbosa individuals of different flower morph have same chromosome numbers. After examining paraffin section of anther, I found that white anther had abnormal tapetum. Therefore, possible causing white anther is not due to odd chromosome set, but is caused by the abnormal tapetum. Greenhouse and growth chamber experiments also showed that temperature and irradiance could influence the percentage of vital pollen of upper stamen. Plants under low light treatment had lower percentage of vital pollen. The adequate temperature and irradiance may increase the percentage of vital pollen of upper stamen, but the situation will not improve the fruiting probability of O. corymbosa due to the absence of long morph individuals in Taiwan. Since O. corymbosa has self-incompatibility and successful pollination is restricted within legitimate pollination, the absence of long morph individuals in Taiwan and low percentage of vital pollen may be important factors contributing to the fruiting failure of O. corymbosa in Taiwan.

並列關鍵字

Oxalis corymbosa ； light ； water ； sexual reproduction ； pollen viability

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