探討台灣紫花酢漿草的繁殖和生長

The studies on reproduction and growth of Oxalis corymbosa in Taiwan

蔡孟穎(Meng-Ying Tsai)

指導教授 ： 高文媛

共同指導教授 ： 陳淑華(Su-Hwa Chen)

國立臺灣大學/生命科學院/生態學與演化生物學研究所/博士(2017年)

https://doi.org/10.6342/NTU201702738

摘要

紫花酢漿草（Oxalis corymbosa），原產於南美洲，具有花柱三型性（tristyly:長花柱型、中花柱型、短花柱型），在台灣缺少有性繁殖的紀錄。先前研究發現：台灣的紫花酢漿草缺少長花柱型，中花柱型個體最多，短花柱型很少，也有半等高型個體；不同花柱型比率很懸殊，可能會造成合適花柱型之間的傳粉機率下降；此外，花粉活性很低可能也是造成紫花酢漿草在台灣缺少有性繁殖的原因之一。本論文延續先前研究，除了針對紫花酢漿草的有性繁殖進行深入探討外，並測量不同花柱型的紫花酢漿草個體在不同溫度下的生長反應，了解溫度對紫花酢漿草的生長與無性繁殖的影響。使用人工授粉方式以檢驗紫花酢漿草是否有傳粉限制（第二章），結果顯示：僅半等高型（黃色花藥）花柱接收中花柱型（黃色花藥）下輪雄蕊的花粉後能產生極少數種子（7顆），其他各種人工授粉組合則沒有產生種子，顯示台灣的紫花酢漿草有少量可孕性的配子，而傳粉上的限制可能是導致其缺乏有性繁殖的一項原因；此外，量測雄蕊與花柱後發現，台灣的三個花柱型個體，下輪雄蕊與雌蕊的高度變異大，並非具有固定高度，這可能會降低傳粉效率。觀察紫花酢漿草在不同發育時期的小孢子囊與花藥（第三章），發現到營養層與中介層細胞液胞化、減數分裂時期之小孢子無妥善分隔（與胼胝體沉降異常或細胞分裂的異常有關）、中介層細胞瓦解時間過晚等異常現象，這些現象導致紫花酢漿草的成熟花粉敗育或者最終沒有正常花粉產生。製作胚珠切片觀察並量化可孕性胚珠比率（第四章）後，發現具有卵細胞的胚珠數量很少，在所觀察的中花柱型（黃色花藥）花的胚珠中有1.7%（2/121）、半等高型（黃色花藥）花的胚珠中有4.3%（7/162）具有5核的胚囊（雌配子體），而半等高型（白色花藥）花的胚珠中，則沒有觀察到任何具有5核的胚囊（0/129），此測量數據和人工授粉實驗結果相符。紫花酢漿草的生長明顯受到生長溫度的影響（第五章），中花柱型個體相對於其他花柱型，僅在15/13℃時累積較多生物量，而在20/15℃，25/20℃和30/25℃溫度處理下，並無差異；且在相同處理溫度下，中花柱型個體並沒有比半等高型個體具有更好的鱗莖生長優勢，雖然如此，相較於半等高型個體，中花柱型（黃色花藥）個體會產生較多、尺寸較小、包覆完全的成熟無性鱗莖，這可能是導致中花柱型（黃色花藥）個體數量較多的原因。

關鍵字

花柱型 ； 花粉萌發 ； 授粉 ； 結實 ； 花藥組織學 ； 雄不孕 ； 小孢子發生 ； 花粉發育 ； 臺灣 ； 花柱三型性 ； 胚珠發育 ； 雌可稔性 ； 溫度 ； 生物量 ； 無性繁殖

並列摘要

In a previous study, I studied Oxalis corymbosa, which is an exotic tristylous [long- (LS), mid- (MS), and short-styled (SS) morph] species, to investigate what limit sexual reproduction of the plant in Taiwan. Results of the study revealed that no sexual reproduction of this species in Taiwan is partly attributed to lack LS floral morph, disequilibrium in proportion of floral morphs (MS morph was the dominant), and low pollen viability. Individuals bearing semi-homostylous morphs (SHS) with white and fully male-sterile anthers were also found in Taiwan. This dissertation aims to answer several questions derived from the previous study (Chapter 1).
Can seeds be produced through hand-pollination? The result of a hand-pollination experiment suggests that O. corymbosa has potential to produce capsules in Taiwan (Chapter 2). However, limitation in pollen transfer and low percentage of fertile gametes result in no seed produced in field. So, what’s wrong with pollen and ovules? To answer this question, the development of male and female gametes were observed. In histological observation of microsporangium and anther development at different stages, several developmental aberrations, including incomplete callose deposition or cytokinesis failure at tetrad stage (MS and SHS morphs) and persistent/highly vacuolated middle layer cells during free microspore stage (SHS morph) were observed. These results reveal that male-sterility of the species is caused by multiple defects during microsporegenesis and pollen development in Taiwan (Chapter 3). High proportion of ovule abortion was frequently observed among floral types. Consequently, five-nucleate embryo sacs (megagametophytes) were only observed in ovules of few SHS-Y (4.3%) and MS-Y (1.7%) types of flowers, but not in those of SHS-W flowers during anthesis stage of O. corymbosa (Chapter 4). The observation of female fertility of O. corymbosa is consistent with the data of hand-pollination experiment. The results of temperature experiments showed that biomass accumulations of O. corymbosa was affected by different temperature regimes (Chapter 5). Individuals bearing MS-Y type flowers grown at low temperature treatment (15/13℃) accumulated more biomass than individuals bearing other floral types, but not at 20/15℃, 25/20℃, and 30/25℃. Moreover, MS individuals did not accumulated more biomass in bulbs than SHS individuals under any temperature regimes. However, MS-Y individuals at 25/20℃ produced more and smaller mature bulbs than individuals bearing other floral types. With more easily dispersed small-bulbs, MS-Y individuals might be able to establish more populations than individuals of other floral types.

並列關鍵字

Floral morphs ； pollen germination ； pollination ； seed-set ； anther histology ； male sterility ； microsporogenesis ； pollen development ； Taiwan ； tri-styled flower morph ； ovule development ； female fertility ； temperature ； biomass ； vegetative propagation

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