三種人工光源對植物生長的影響及其可能的植物賀爾蒙調控機制

光如何影響植物的生長，是生物學家研究許久的一個問題；然而，仍有許多現象是無法被解釋清楚的。多數的研究著重在控制單一光源/單色光源做為變因，建立分子機制的模型，來描述其影響。但是以下兩點仍未被充分探討：（一）某些單色光（如綠光）對植物的影響；（二）在全光譜中使用不同波長的比例又會產生什麼影響。本研究使用三種不同的室內人造光源，與兩種植物：綠豆（V. radiata）和阿拉伯芥（A. thaliana，Col 0），利用相互比較的方法來了解不同成分的光譜對植物生理生長的影響。實驗從植物形態、生化指標到分子生物的層次，來瞭解其間的差異與成因。結果發現鹵素燈（HL）會使得綠豆與阿拉伯芥在發芽與早期發育期具有較高的生物量（biomass），生長情形較佳；但在中後期，鹵素燈下的阿拉伯芥的生物量就遠遠落後螢光燈管（FT）和紅/藍發光二極體（LED），不過會較早開花和具有較多花序頂（inflorescence apex）。這顯示不同階段的植物生長，對光會有不同的需求。鹵素燈擁有較多的紅外光，可能誘發植物的避蔭反應（shade avoidance response），及產生較高的葉溫是產生差異的可能原因。在生化檢測上，生長情形較佳的植物，如鹵素燈下的綠豆，或螢光燈管下30天以後的阿拉伯芥，會有較多營養物質累積（如碳水化合物），且它們的過氧化壓力指標-丙二醛（malonaldehyde）也比較低，顯示其承受的壓力較低，抑或是處理、適應的能力較佳。同時，葉綠素螢光（chlorophyll fluorescence，Fv/Fm）測量也呈現相似的結果：生長情況較佳的植物，所承受的逆境壓力較小。在分子層次上，選擇著重在植物賀爾蒙（phytohormones）生合成路徑上的基因；但發現這些基因的表現在三種光源之間並沒有太大差異。主要原因可能是賀爾蒙作用的位置仍較上游，並有互相調控的機制以維持恆定，因此較不會顯現差異。但仍有一些基因的表現可與生理生長建立關聯，例如參與生長素(auxin)合成最後一步的酵素AAO1（acetaldehyde oxidase 1）在五十天裡的時間點中都有很高的表現量，且在第十天和第四十天時達統計顯著；其扮演的角色可能在於調控植物的避蔭反應（shade avoidance response）。

關鍵字

人工光源；發光二極體；光生理發育；阿拉伯芥；綠豆；即時定量聚合酶連鎖反應；植物賀爾蒙

並列摘要

This study investigated the effects of three artificial light sources on the growth of plants. We used mung beans (V. radiate) and Arabidopsis (A. thaliana, Col 0) as model plants. To compare the effects of three light groups on the morphological, biochemical, and molecular alternation. The results showed that both the beans and Arabidopsis had more biomass at seedling stage when grown under halogen lamps (HL). However, at later stages, HL-Arabidopsis had the smallest biomass, far less than grown under fluorescence tubes (FT) and red/blue light-emitted diode (LED), and had more inflorescence apex and flowered earlier. The spectrum of HL contained more infar-red (FR), which will induce the shade avoidance response (SAR), and the lamp could generate higher leaf temperature, both may contribute to the major differences between HL and other light sources. Biochemical measurement agreed with the results of morphological examination. HL-mung beans and FT- Arabidopsis after 30 DAP (day after planted), have more carbohydrates accumulation (e.g. c), and showed lower concentration of MDA (malonaldehyde), which is an indicator for oxidative stress. These plants perhaps experienced less stress or had better ability to dealing with the stress. Chlorophyll fluorescence was resemble to draw the conclusion that those “healthy” plants were under less stress. At molecular level, we checked the expression of genes involved in the phytohormones biosynthesis pathway. The expression of these genes displayed not much difference across the three groups of light sources. The hormones are probably the signals at the upstream of their response, and a network-style of regulation tends to offset any perturbation to the system. However, the results can still provide some evidence for the involvement of hormone regulation. For example, AAO1 (acetaldehyde oxidase 1), an auxin related genes, which participates in the last step of auxin synthesis, was upregulated during plant growth, and was statistically significant at 10 and 40 DAP. It probably played a role of signaling in SAR.

並列關鍵字

artificial light ； Light-Emitting Diodes (LEDs) ； photomorphology ； Arabidopsis ； mung bean (V. radiata) ； quantitative real-time polymerase chain reaction (qRT-PCR) ； phytohormones

參考文獻

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三種人工光源對植物生長的影響及其可能的植物賀爾蒙調控機制

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