三種狗尾草屬植物在不同光環境表型可塑性的比較

Phenotypic plasticity of three Setaria species grown under different light environments

劉彥治(Yan-Zhi Liu)

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/NTU201702804

摘要

颱風草能生長在森林邊緣與林下，因此比一般C4具有較廣的光環境棲地。先前研究指出颱風草具有表型可塑性，且其葉片有葉綠體移動現象，使其可以在不同的光環境下生長。本研究比較狗尾草屬的C4植物，分別是小米 (生長在開闊地)、颱風草 (生長在森林邊緣與林下) 與皺葉狗尾草 (主要生長在林下) 在不同光度環境下生長植株其葉片形質、光合作用表現與生長反應，然後計算其表型可塑性指數，以檢驗颱風草是否有最高的表型可塑性：並探討能在林下生長的颱風草與皺葉狗尾草是否比小米有較明顯的葉綠體移動反應與較快的光合作用反應能力。
結果顯示小米葉片面積隨生長光度降低而減小，颱風草和皺葉狗尾草則呈現相反的反應 (兩者反應程度相似)。隨生長光度降低，三者葉片的單位乾重葉面積均增加、葉肉組織均變薄、葉綠素a / b比降低 (小米的反應最大)、單位乾重之葉綠素含量增加 (皺葉狗尾草的反應最大)、暗呼吸速率及光補償點均下降、地上部 / 地下部生物量的比值增加；計算後發現小米的表型可塑性指數 (RDPI值) 最高，而颱風草最低。比較三物種，在全光環境下，小米有最大的葉片面積及最高的光飽和淨光合作用速率和光飽和點，而在中光和低光環境下，颱風草有最大的葉片面積，在低光環境下，皺葉狗尾草有最低的暗呼吸作用速率與光補償點。
藍光可以誘導三物種的葉綠體移動呈現聚集或避光反應，三物種在全光環境下生長時，照射弱光或環境照光度低時有顯著的葉綠體聚集反應；而颱風草與皺葉狗尾草在低光環境生長時，在高照光度時其葉綠體有明顯的避光反應，推測當斑光發生時，該反應可使葉片避免吸收過多的光造成光傷害。三物種光合作用速率與氣孔導度受光誘導的反應皆相當快速；與其他兩物種相比，生長在遮陰環境下的颱風草達到最高光合作用速率的時間較短，也許可以較有效率地利用斑光。

關鍵字

表型可塑性 ； 葉綠體移動 ； 斑光 ； 狗尾草屬 ； C4植物 ； 光環境

並列摘要

C4 plants are mainly distributed in habitats with high light and high temperature. Setaria palmifolia, a C4 plant, can grow in a broad range of light environments, such as in forest edge and understory. A previous study implied that phenotypic plasticity and chloroplast movement response confer S. palmifolia ability to grow under varied light evironments. Leaf characters, photosynthetic performances and growth of three C4 plants, S. italica (distributed in open habitat), S. palmifolia (in forest edge and understory) and S. plicata (mainly in understory), grown under different light regimes were measured in this study. The relative distance plasticity index (RDPI) was calculated for the comparison of phenotypic plasticity among the studied species. Chloroplast movements and photosynthetic induction response were also investigated to evaluate whether shade-tolerant S. palmifolia and S. plicata have more apparent chloroplast movements and better efficiency in utilizing sunflecks than S. italica.
Results showed that leaf size of S. italica decreased but that of S. palmifolia and S. plicata increased (both with similar magnitude of response) as growth light level decreased. As growth light level decreased, the three species showed reduction in mesophyll thickness, chlorophyll a / b ratio (S. italica the highest response), respiration rate and light compensation point, while increased in specific leaf area, chlorophyll content per unit mass (S. plicata the highest response) and aboveground to belowground biomass ratio. Overall, S. italica had the highest RDPI, and S. palmifolia the lowest. In comparison of the three species, S. italica had the largest leaf size, photosynthetic capacity and light saturation point under full-sun regime while S. palmifolia had the largest leaf size under intermediate and low light regime. Under low light regime, S. plicata had the lowest respiration rate and light compensation point.
Three species had blue light induced chloroplast movements (accumulation and avoidance response). Apparent chloroplast movements (accumulation response) were found in leaves of full-sun grown plants. S. palmifolia and S. plicata showed significant avoidance response when they were grown under low light regime. The avoidance response of chloroplast might reduce the risk of photodamage caused by excessive light (e.g., sunflecks) when S.palmifolia and S. plicata growing in forest understory. Three Setaria species had rapid photosynthetic and stomatal responses in response to changes in light intensity, from 20 to 1600 μmol m-2 s-1. When grown under shaded environment, S. palmifolia achieved light-saturated photosynthetic rates in relatively shorter time than the other two specise. Accordingly, S. palmifolia might have better efficiency in utilizing sunflecks than the other two species.

並列關鍵字

Phenotypic plasticity ； Chloroplast movement ； Sunfleck ； Setaria ； C4 ； Light environment

參考文獻

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