不同光質對甘藷小苗光合作用效率、碳水化合物代謝及抗氧化能力之影響

The effects of different light qualities on the photosynthesis efficiency, carbohydrate metabolism and antioxidant capacity of the sweet potato seedings

林國英(Kuo-Yin Lin)

指導教授 ： 王玉麒

國立臺灣師範大學/理學院/生命科學研究所/碩士(2011年)

摘要

甘藷（Ipomoea batatas (L.) Lam.）葉是重要的抗氧化蔬菜，發光二極體（Light Emiting Diode, LED）則由於可改善傳統燈具壽命短、發熱大和發光效率差等缺點，並提供包括光質、光量、給光頻率及工作比等特定給光條件，成為近年來積極開發之新興人工光源。本論文利用LED提供甘藷小苗藍光（470 nm）與紅光（660 nm），除了探討抗氧化特性外，亦分析光合效率與碳水化合物的代謝受不同光質的影響情形，探討不同光質對甘藷小苗生理之影響。
透過葉綠素螢光數據，經藍光、紅光或全光5天照射處理後，皆不至於對甘藷小苗光合系統Ⅱ造成破壞。由於紅光組甘藷小苗葉片之NPQ明顯低於藍光或全光處理，根據前人指出NPQ與zeaxanthin具正相關性，推測紅光會降低甘藷葉生合成zeaxanthin。
抗氧化能力上，經藍光、紅光和全光處理後之甘藷小苗葉片在glutathion還原態（GSH）及氧化態（GSSG）的含量、ascorbate peroxidases（APX）活性和superoxide dismutase（SOD）活性上並未呈現顯著差異，但藍光處理之葉片表現較高的catalase（CAT）活性，且經藍光或紅光處理後之葉片H2O2含量均較全光低，推測藍光組可透過CAT降低活氧化物的累積。
經測定可溶性醣類含量、澱粉含量與醣類代謝相關酵素活性，顯示不同光質雖未在澱粉含量造成影響，但藍光處理之葉片內葡萄糖、果糖及蔗糖含量皆明顯高於紅光處理，推測與藍光組較紅光組有較高之sucrose phosphate synthase（SPS）和invertase（INV）活性有關。此外全光處理之葉片具較高之acid INV和alkaline INV活性，紅光處理的acid INV和alkaline INV活性則均較藍光處理為低。不同光質下醣類代謝相關酵素活性以SPS和INV表現出顯著差異，但Real-time PCR偵測各酵素基因表現強度並無差別，推測此二者活性應受後轉譯調節所影響。不同光質5天照射雖未對葉片氣孔密度造成影響，但以藍光組氣孔開啟比例最高。
總體而言，藍光處理之甘藷小苗生長良好、有較高之抗氧化能力，葉片內葡萄糖、果糖及蔗糖含量均較高，也具有較高的氣孔開啟比例，顯示在甘藷小苗生長上，藍光較全光、紅光為佳。

關鍵字

光質 ； 發光二極體 ； 甘藷小苗 ； 光合作用效率 ； 碳水化合物代謝 ； 抗氧化能力

並列摘要

The leaf of sweet potato (Ipomoea batatas (L.) Lam.) is an important antioxidant vegetable. The light emitting diode (LED) is a promising artificial light source because of its small mass and volume, and can provide specific light quality, light quantity, light frequency and duty ratio. This paper uses the LED as an artificial light source to provide blue light (470 nm) and red light (660 nm) for sweet potato seedings, and discusses the antioxidant capacity, photosynthesis efficiency, and carbohydrate metabilism of the sweet potato seedings cultivated under different light qualities.
The data of chlorophyll fluorescence showed that photosystemⅡof the sweet potato seedings cultivated under blue, red or full-light for 5 days was not destroyed. NPQ of the sweet potato leaves cultivated under red light was significantly lower than that under blue or full-light. According to the previous research data, we can suggest that the leaves of sweet potato under red light might reduce the biosynthesis of zeaxanthin.
The reduced glutathion (GSH) content, oxidized glutathion (GSSG) content, ascorbate peroxidase (APX) activity and superoxide dismutase (SOD) activity of the sweet potato leaves cultivated under blue, red or full-light for 5 days didn’t show the significant difference, but catalase (CAT) content of the sweet potato leaves cultivated under blue light was higher, and H2O2 content of the sweet potato leaves cultivated under blue or red-light was lower than that under full light. We can presume that the reactive oxygen species content of the sweet potato leaves cultivated under blue light reduced by CAT.
The results of the contents of carbohydrates and the activities of the enzymes to participate in carbohydrate metabilism showed the different light qualities didn’t affect starch content of the sweet potato leaves, but glucose, fructose and sucrose contents of the sweet potato leaves cultivated under blue light were remarkably higher than those under red light. We can speculate that the activities of sucrose phosphate synthase (SPS) and invertase (INV) of the sweet potato leaves cultivated under blue light were higher than those under red light was the reason for foregoing results. Furthermore, the sweet potato leaves cultivated under full light had higher activities of acid INV and alkaline INV, and those under red light had lower activities of acid INV and alkaline INV than those under blue light. The activites of SPS and INV of the sweet potato leaves cultivated under blue, red, or full-light had significant difference, but the expressions of gene of SPS, sucrose synthase (Susy) , and INV displayed by Real-time PCR were not different. Therefore, the activity of SPS and INV might be affected by post-translation. Although the densities of the stroma of the sweet potato leaves cultivated under blue, red, or full-light didn’t have significant difference, the ratio of the open stroma of the sweet potato leaves cultivated under blue light was the highest.
As a whole, the sweet potato seedings cultivated under blue light were growing abundantly, and the leaves of those had higher antioxidant capacity, more glucose, more fructose, more sucrose, and higher ratio of the open stroma. Those results indicate that blue light is better than red or full-light for sweet potato seedings.

並列關鍵字

light quality ； light emitting diode (LED) ； sweet potato seeding ； photosynthesis efficiency ； carbohydrate metabolism ； antioxidant capacity

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