- 學位論文
水稻穎果充實期間其氧氣濃度分析方法之建立
Establishment of the Method for Oxygen Concentration Measurement in Rice Caryopsis during Grain-Filling Stage
摘要
水稻於穀粒充實期間遭遇高溫，會導致穀粒白堊質形成，白堊質形成是由於異常堆疊澱粉導致透光受阻，影響外觀品質。氧氣濃度的維持為穀粒內澱粉、蛋白質、脂肪等大分子生合成及累積之必需。前人研究顯示種子內部為低氧狀態，此外，高溫可能加劇種子內部低氧情形，因此，高溫下穀粒內部的氧氣濃度與白堊質形成應有極大的關係。然而，國際間尚未建立測量水稻穎果內部氧氣濃度的方法。為探討高溫下水稻穎果的氧氣狀態與白堊質生成之關係，本研究以建立水稻穎果內部氧氣濃度分析方法為首要目標，以台灣良質米台稉9號為材料，於穎果充實期處理高溫 (35 oC)及常溫 (25 oC)，並以積溫為依據，於各處理分別取樣相同積溫之穎果。主要以planar oxygen sensor ( PreSens, Germany )偵測穎果中氧氣濃度，同時使用oxygen microsensor ( PreSens, Germany )輔助驗證實測之氧氣濃度，探討高溫下穎果內氧氣濃度變化與白堊質形成之關係。planar oxygen sensor可以2維平面圖像呈現穎果橫切面的訊號，並以色階變化代表訊號值大小。進一步將圖像數據化，結果顯示在各生育期之穎果內部的氧氣含量均由外到內遞減，表示穎果內部處於較低氧的狀態。同時在高溫情況下，穎果內部的氧氣濃度有較常溫低之趨勢，但並沒有達統計上的顯著水準，推測原因為測量重複數過少，導致測量值間標準差過大。綜上所述，本研究所建立之測量水稻穎果氧氣濃度方法，初步揭示了不同生育期及不同溫度處理之穎果內部氧氣濃度變化情形，爾後可進一步修飾、改善該方法，以期對穎果發育時其內在氧氣濃度狀態、其與生理過程之關係、及與栽培環境、米質形成間的關係有更進一步的瞭解。
並列摘要
Rice chalky grain formation under high temperature is known to be related to the metabolic alteration under stress. Internal oxygen concentration is crucial for maintaining energy balance for starch, protein, and lipid assimilations during rice grain development. Documents revealed that hypoxia metabolism may occur in developing endosperm under high temperature. Therefore, it has hypothesized that internal oxygen level might be correlated with the chalkiness formation of rice grain under high temperature. However, no method for measuring internal oxygen concentration in rice grain has been developed in the world so far. Thus, the aim of the present study was to establish possible methods for measuring oxygen level in developing rice grain, and hope to clarify the relationship between oxygen concentration and grain chalkiness formation under high temperature. A high quality cultivar Tai-keng 9 (TK 9) was used as material which were exposed to high temperature (35 oC) or control temperature (25 oC) treatment during the grain-filling stage . Caryopsis samples were collected at different development stages base on the cumulative temperature after flowering. In this research, a planar oxygen sensor (PreSens, Germany) was used to measure internal oxygen of caryopsis and an oxygen microsensor (PreSens, Germany) was used to verify the value of oxygen concentration. The results showed that oxygen concentration of caryopsis decreased from external to internal at every grain-filling stage, that is, it is hypoxia at central endosperm. At the same time, caryopsis oxygen concentration under high temperature seemed to be lower than the control, although it didn’t show statistically significant difference. Due to the high time consuming for the oxygen measurement of rice caryopsis, the number of experimental replicate was very much limited; which would lead a large measurement variation at the present study. In summary, the present study has established the method of measuring internal oxygen concentration in developing rice caryopsis, and showed the preliminary results about the change of oxygen concentration at different stages. In the future, the method can be modified and improved to understand the relationship among internal oxygen level, metabolism process, and grain quality formation, especially under stressful environments.