以多通道螢光光譜影像系統與螢光指標探討甘藍苗水份逆境之研究

臺灣的蔬菜育苗主流為穴盤育苗，由於育苗期間的水份管理與移植後的成長息息相關。為了確保苗株的品質，提高苗株移植後的存活率及產量，對於穴盤苗株進行水份狀態的偵測有其必要。植物生長過程中，容易遭受包括水份等不同逆境的影響，導致生長受到干擾，使光合作用產生變化，造成植物螢光表現的變異。因為由植物葉綠素螢光之反應，能探討植物遭遇逆境的狀況，故可利用以偵測苗株之水份逆境，藉以管理蔬菜育苗時之水份供應。本研究使用八組藍光LED之燈組作為螢光激發光源，四部攝影機組成之同步多通道影像擷取系統及以鋁擠型、黑色布幔製成之暗室設備，並利用FXGPWIN、Visual C++、Matlab等軟體撰寫系統之控制及分析程式，開發一套多通道螢光光譜影像檢測系統。系統選用460 nm、690 nm、720 nm及740 nm四個波長之濾光鏡，擷取於此四種波長下之不同水份逆境處理之甘藍苗株葉片的螢光影像，並量測葉片水份含量及水份潛勢，以探討其與螢光指標之關係。研究所開發之多通道螢光光譜影像檢測系統，能有效量測苗株葉片之螢光影像，並建立葉綠素螢光淬息曲線，以求得最大螢光值Fm與穩態螢光值Fs。同時，本研究也建立一個動態螢光指標（dynamic fluorescence index, DFI），僅需170秒就能完成該指標的量測，大大縮短傳統上之量測時間。分析結果得知，使用720 nm波長之DFI螢光指標預測甘藍苗株葉片之水份潛勢更優於使用傳統之Rfd螢光指標，DFI及Rfd對水份潛勢之相關係數r各為0.944及0.795，標準誤差SEE各為0.286及0.525 Mpa。在去除高水份逆境之樣本後，DFI對水份潛勢之相關係數僅微微降低至0.861，不同於Rfd的則降低許多，其r由0.795降至0.416，可顯示DFI在植物遭遇較低水份逆境時仍具有高的預測能力，因此DFI對水份之逆境具有敏感性，且能應用於逆境尚未造成傷害時之檢測，可防範水份逆境於未然。

關鍵字

螢光影像；螢光指標；水份逆境；苗株；光合作用

並列摘要

Most of vegetable seedling nurseries in Taiwan adopt plug tray system for seedlings production. The proper water management during the seedling nursery is important to the growth after transplanting. In order to ensure the quality of the seedlings and to improve the production after transplanting, the water status of the plug seedlings is necessary to be monitored and detected. Several kinds of stresses such as water stress may affect the growth of plants due to the variation of photosynthesis and result in the changes of fluorescence reaction. The status of plants under water stress can be assessed according to the response of chlorophyll fluorescence. Therefore, the technology which can measure water stress of plants is needed for irrigation mangement during seedling growth. In this study, a multi-channel fluorescence spectral imaging system was developed, which consisted of eight sets of blue-LED fluorescence inducing light, a multi-spectral imaging system with four CCD cameras, and a dark chamber. The control and analysis programs of the system were programmed by using FXGPWIN, Visual C++, and MATLAB. Filters with four wavelengths, 460 nm, 690 nm, 720 nm, and 740 nm were used to detect the fluorescence emission spectra of the leaves of cabbage seedlings under various water stresses. After measuring water contents and water potential of the leaves, the relationship among them and the indices of fluorescence can be found. The multi-channel fluorescence spectral imaging system was proofed that can effectively detect fluorescence images of seedling leaves, and then get maximum fluorescence (Fm) and steady-state fluorescence (Fs) from the fluorescence quenching curve of them. Besides, a novel fluorescence index (dynamic fluorescence index, DFI) was developed in this study. With the proposed DFI, highly correlated data (r = 0.944) and low standard error of estimate (SEE = 0.286 MPa) to the water potential values can be obtained from a single channel around 720 nm and with shorter imaging times (170 seconds). The coefficient of correlation reduced to 0.861 after eliminating samples with high water stresses, indicating that DFI still has high predictability under condition of low water stress to plants.