生物為了獲取更多的生存資源而演化出能夠適應環境的性狀及能力，對於植物而言，光是行光合作用最根本也最重要的能量，因此植物演化出了尋找光源的能力 向光性。植物藉由葉片裡的光接收器 photoreceptor 來吸收並感測光源的方向，並調控植株體內的生長素使其運輸至光源的背側 造成兩側生長速度差 異，促使植株朝向光源方向生長。在以往的研究中，向光性的研究大多 以植物的莖為主要觀察部位，由莖帶動植物朝向光源方向生長，使植株能獲取更多的光源，然而葉子才是行光合作用的最主要器官，但葉子本身是否具有獨立向光性反應仍不是很清楚。
在本實驗中，我將植株的莖固定在鐵條上，並將光源設置在植株的正下方，在進行不同色光引導實驗後，發現番茄的葉子會大幅度的朝光源方向彎曲，且只有受到藍光及白光照射時會有彎曲反應。為了瞭解葉子彎曲的主要部位在哪，我將葉子的葉片部分剪下並進行光引導實驗，發現葉子不論在有無光刺激的情況下皆不會彎曲。在生長素運送抑制實驗中，葉子受到生長素運送抑制劑NPA的影響，不論是否受到光的刺激，皆會大幅度的向下彎曲。此外為了瞭解葉子向光性在不同植株間的差異，我以與番茄同科但葉型為單葉的燈籠草Phsalis angulata以及與番茄不同科但葉型同為複葉的大豆Glycine max進行光引導實驗，結果顯示大豆在藍光與白光的刺激下葉子會大幅度向下彎曲。在燈籠草的結果中，燈籠草葉子在受到任一色光刺激後，葉子彎曲變化量皆為負數，意即所有葉子的彎曲度都比進行實驗前還要小，且各色光的變化量均相近，但在受到白光和藍光刺激後的負數變化量相對較小。此實驗顯示葉子向光性的反應在各種植物上皆有類似的表現，但表現的反應以葉型的不同而有所差異 ，其中以複葉的葉型反應較明顯，也較適合作為葉子光性實驗的觀察對象。根據我的研究結論顯示，植物確實具有獨立的向光性反應，且根據植物不同的葉型會有不同的反應模式，植物的向光性是植物為了適應環境並獲取光源的一種手段是植物為了適應環境並獲取光源的一種手段，因此瞭解植物向光性對於，因此瞭解植物向光性對於未來與植物適應環境相關的研究有重要的影響。未來與植物適應環境相關的研究有重要的影響。

To obtain more living resources, organisms evolve traits and abilities that can adapt to the environment. For plants, light is one of the most important things for photosynthesis. Thus, plants evolve the ability to find light sources, which is known as phototropism. Phototropism is an important tropism in plants. Plants detect and perceive the sunlight by photoreceptors and regulate the auxin distribution to cause the different growing speeds between the light side and the shade side of the stem. The plants can grow toward the light side. In previous research, most of the research about phototropism was focused on the bending of stems or cotyledons in the early development of seedlings. Although leaves are the major organs for doing photosynthesis, the mechanism of phototropism in leaves remains unknown.
In this study, I fixed the plant stem on an iron stick and put the light at the bottom of the plants to prevent the stem from bending. After giving different colors of light treatment, the leaves of tomatoes bent down toward the light. The curving reaction only occurred when white light and blue light were treated, but did not under dark condition, green light, and red light treatment. To examine which part the curving reaction mainly occurred, I cut the blade parts of leaves and left the petioles on the stem then treated them with light. The result showed that no matter if I gave them light stimuli or not, the leaves with no blades, did not curve. In the auxin transport inhibitor experiment, the leaves curved a lot no matter if I gave them light stimuli or not. To know the different reactions of leaves phototropism between different species of plants, I did the same light stimulus experiment on soybeans (different family to tomatoes, but the same leaf type) and Physalis (the same family as tomatoes, but different leaf type). The results showed that the leaves bent down toward the light after being treated with blue and white light in soybeans. And the angle change had a similar pattern to the curvature changes of tomatoes. In Physalis angulata, the curvature changes of all samples were negative. It means that the curvature of Physalis leaves were all lower after light treatment. The value of Δcurvature was higher in the blue light and white light treatment. These results suggested that leaves had their way to do phototropic response and that the reaction mode depended on their leaf type. According to my study, plants do have an independent phototropic response, and there were different response modes according to different leaf types of plants. The phototropism of plants is a means for plants to adapt to the environment, so understand phototropism has important implications for future studies related to plant adaptation to the environment.

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