氮素對高溫下水稻穀粒品質形成之緩解作用之研究

Study of the Amelioration Effect of Nitrogen on Rice Grain Quality Formation during Grain-Filling Stage under High Temperature

楊凡萱(Fan-Hsuan Yang)

指導教授 ： 盧虎生

國立臺灣大學/生物資源暨農學院/農藝學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.10414

摘要

高溫環境下常會造成水稻產量及品質的下降。本研究室先前研究指出，在穀粒充實期添加氮素可以舒緩高溫對外觀品質之傷害，但氮素對高溫下儲藏性物質及碳-氮代謝循環之影響尚不了解。本論文利用良質米栽培品種台稉9號為材料，在穀粒充實期進行高溫及外添加氮素處理，收取不同發育階段之穎果進行分析。試驗中分析成熟穀粒之外觀品質、儲藏性物質、生理指標分析，並利用HPLC分析穎果之胺基酸及有機酸的變化，並且利用real-time PCR分析相關之基因表現，期望可以了解在各處理下之碳-氮調節機制，及對於穀粒品質之影響。
試驗結果顯示外加氮素有助於緩解高溫對穎果的危害，使得水稻糙米之完整米率提升、嚴重白堊質之比率下降。在生理分析試驗結果方面，在高溫下添加氮素可以使穎果之葉綠素降解減緩，並使澱粉恢復並使ATP、pH值、糖類、胺基態氮及儲藏性蛋白質含量較高溫處理下提升。而在代謝物方面，高溫處理下有機酸malate及胺基酸alanine累積，malate之累積被認為可能導致細胞之酸化，而alanine之累積可能參與了pH之平衡。在高溫下添加氮素，可減少malate，增加succinate，並且使alanine累積量更高，可能因而減緩了高溫下之酸化現象。另外，在real-time PCR分析結果顯示，高溫下添加氮素可恢復澱粉之合成並緩解澱粉之降解，並部分恢復儲藏性蛋白質之合成，並且連結碳-氮轉換之間的基因也隨之提升。其主要之機制是由於高溫下添加氮素，可增加有機酸及胺基酸含量，並透過AlaAT、GabaAT及OGDH，將胺基酸及糖解作用產物轉化，以平衡細胞之pH並透過non-cyclic TCA cycle產生ATP。因此在高溫處理下碳-氮之間之流轉的確會受到外加氮素而提升，而氮素之添加可能幫助pH之平衡，並且使蛋白質及澱粉之累積得以維持，改善稻米白堊質的現象。
本研究探討了氮素添加與高溫對稻米品質之關係，並提出一個高溫下碳-氮之間的反應之假說，但其間詳細之調控機制仍需要後續的試驗加以釐清。

關鍵字

高溫 ； 水稻 ； 穎果 ； 碳氮 ； 白堊質 ； 氮素 ； 胺基酸 ； 有機酸

並列摘要

High temperature leads to yield loss and quality defects of rice. Our previous studies showed that applying nitrogen fertilizer during grain filling stage could relieve the effects of high temperature. In this study, rice cultivar TK9 was used as experimental material. Treatments of high temperature with or without N fertilizer top dressing were performed during grain filling stage. Rice kernels appearance, major storage components and physiological responses were determined after harvest. In order to understand the regulatory mechanism between nitrogen and carbon metabolism under treatments, HPLC was utilized to analysis the fluctuation of profile for amino acids and organic acids. Real-time quantitative PCR was further utilized as a tool to realize the responses of the gene expression involved in related physiological processes.
The results showed that applying N could ameliorate the defective effects of high temperature treatment by increasing sound rice grain rate and reduce the severity of chalkiness. In further physiological analysis also showed that applying N under high temperature could decelerate the degradation of caryopsis chlorophyll and partially recover the pH value, and the content of ATP, sugar, amino nitrogen, starch and protein in brown rice. The measurements of metabolite reveal that under high temperature, the contents of malate and alanine were elevated. Malate may cause cell acidification and alanine may serve the purpose of pH balance. Applying N could reduce the amount of malate and increase succinate and alanine levels, which may represent the relief from acidosis under high temperature.
Results of real-time PCR showed that applying nitrogen increased expressions of genes involved in synthesis and ameliorating the degradation of starch. Also, the genes of storage protein such as prolamin 7 and 19kD globlin which were inhibited under high temperature could also recover expressions by applying nitrogen. Moreover, the genes connecting up the C-N interactions such as AlaAT, GabaAT and OGDH were elevated under high temperature and the expression of these genes were much higher by applying nitrogen. These genes mainly mediate the conversions and tramsaminations between amino acids and organic acids. Amino acids such like alanine would help to balance cytosolic pH value and its by-product α-ketoglutarate would enter the non-cyclic TCA cycle in order to generate ATP.
Our results of storage components and metabolites indicate that the main regulatory flows between C-N were increased by the nitrogen application under high temperature. Applying nitrogen not only provide the metabolites to deal with high temperature stress but also sustain the accumulation of protein and starch, which in turn ameliorate the chalkiness of rice kernels.
In this study, I have investigated the regulatory mechanism between C-N and proposed a rationale scheme to explain the relationship among nitrogen, high temperature and rice grain quality. In order to clarify the in-depth regulatory network, further analysis is need to be conducted.

並列關鍵字

high temperature ； rice ； caryopsis ； C-N ； chalky ； amino acid ； organic acid

參考文獻

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