玉山箭竹在不同光環境下葉片形態與生理特性的比較

The comparisons of leaf morphological and physiological traits of Yushania niitakayamensis growing under different light environments

吳昆松(Kun-Sung Wu)

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(2017年)

https://doi.org/10.6342/NTU201702736

摘要

玉山箭竹 (Yushania niitakayamensis) 是多年生、禾本科竹亞科植物。前人研究及野外觀察發現：玉山箭竹可在開闊地形成草原 (植株高度< 2 m) 或在冷鐵杉林下生長 (植株高度> 2 m)。本研究探討：一、生長在不同生育地的玉山箭竹，除了植株高度外，其葉片形態、解剖構造及光合作用特徵是否有差異，二、上述特徵差異是否和其適應不同光環境有關；三、造成這些差異的原因是表型可塑性或生長在不同環境的族群已具有遺傳變異；並初步測量玉山箭竹其種子發芽和小苗生長。
比較生長在合歡山草原和林下的玉山箭竹，發現不論在哪一個季節，兩族群其葉長/寬比、葉片面積、氣孔密度、葉厚、單位乾重葉綠素含量均有顯著差異，這些差異會影響葉片光線吸收、散熱、水分散失及光合作用；觀察葉片切片發現林下植株葉肉的紡錘細胞 (特化的葉肉細胞) 細胞間隙較草原植株多。將草原與林下的玉山箭竹移植，種植於全光照及遮陰處理下1個月及8個月後，發現同一族群在兩種光度處理下，具有不同的葉片形質及氣體交換特徵，且紡錘細胞間隙的出現與生長光度有關，顯示玉山箭竹具有表型可塑性，且生理特徵對於光環境改變的反應速度比形態特徵快；不同生育地來源植株在相同光環境下，大部分的葉片特徵沒有顯著差異，然而有一些特徵，例如葉長/寬比、光飽和淨光合作用速率及光使用效率差異仍然存在，且葉厚、單位面積氮含量及水分使用效率等特徵的表型可塑性程度也不同，顯示不同生育地的族群在葉片特徵上已開始有遺傳分化的情形。
播種經過篩選且去除稃片的玉山箭竹種子，發現其發芽時間並不一致，可能有休眠期，在播種後第35天開始發芽，累積到第187天，發芽率達67.5%。發芽後的小苗，在全光照及遮陰處理下生長6個月後，遮陰處理植株其葉長、葉寬、葉面積及第二節間長顯著大於全光照處理植株，植株高度則沒有顯著差異。

關鍵字

玉山箭竹 ； 葉片特徵 ； 表型可塑性 ； 遺傳分化 ； 紡錘細胞 ； 種子萌芽及小苗生長

並列摘要

Yushania niitakayamensis (Bambusoideae; Poaceae), a perennial bamboo species, grows in full sunlight forming meadows or dominates the forest understory. In this study, I aimed to answer following questions. (1) In addition to plant heights, are there differences in leaf morphological, anatomical and photosynthetic traits between Y. niitakayamensis populations? (2) What are the effects of the aforementioned differences on Y. niitakayamensis growing in two habitats with different light regimes? (3) Are these differences caused by phenotypic plasticity or genetic variation? I also investigated seed germination and seedling growth of Y. niitakayamensis.
Significant differences in leaf length/width ratio, leaf area, stomatal density, leaf thickness, and chlorophyll content per unit mass were found between plants growing in meadow and in forest understory at He-huan mountains. Plants growing in forest understory had more fusoid cells (specialized mesophyll) intercellular space than plants growing in meadow. These differences would result in differences in leaf light absorptance, heat dissipation, water-use efficiency, and photosynthetic performance between the two populations. Plants from both habitats were transplanted and grown under two light treatments (full sun and 70 % shading) for eight months. Y. niitakayamensis expressed plastic phenotypes in leaf morphological, anatomical and photosynthetic traits in response to contrasting light environments. The adjustments in leaf physiological traits were faster than morphological traits in response to different light regimes. The occurrence of fusoid cell intercellular space is associated with growth light regimes. However, most of the aforementioned differences in leaf traits disappeared when plants from both habitats grown under the same light regime. Nevertheless, plants from different habitats showed differences in some leaf traits (e.g., leaf length/width ratio, light-saturated net photosynthetic rate and apparent quantum yield) and the degree of phenotypic plasticity in leaf thickness, nitrogen content per unit area and water-use efficiency in response to different light regimes indicating some genetic differentiation between the two populations.
The seeds, after palea and lemma being removed, of Y. niitakayamensis were not germinated synchronously indicating seed dormancy. Totally about 70 % of seeds were germinated, 187 days after sowing. The germinated seedlings were then grown under two light treatments (full sun and 70 % shading). Significant differences in leaf length, width, area, and the length of second internode, but not in plant height, were found between seedlings grown in different light environments for six months.

並列關鍵字

Yushania niitakayamensis ； leaf traits ； phenotypic plasticity ； genetic differentiation ； fusoid cell ； seed germination and seedling growth

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