氮肥及鎘、鉻與鉛對水稻幼苗生長與反射光譜之影響

Abstract

考量到重金屬可由土壤累積進植株內，並藉由攝食而進入人體而產生危害，監測系統的建立有其必要性，因此希望能建立即時且非破壞性之監測方式以預估土壤有效性重金屬汙染濃度與植體累積金屬含量。本研究以水稻(Oryza sativa)品系台中秈10號及台稉9號(TCS10 and TK9)幼苗為材料，以50、100及200 ppm之氮素濃度分別與鎘(0、50、100及200 µm)、鉻(0、100、200及500 µm)與鉛(0、100、200及500 µm)三種重金屬進行複因子水耕試驗，藉此來模擬田間不同濃度氮肥管理下，土壤溶液中有效性重金屬對水稻幼苗造成之影響，處理一周後測定葉面反射光譜，以反射率計算植生指數 (vegetation index)，結合地上部植體重金屬含量資料進行一次與二次多項式回歸分析，並從中建立預測模型。結果顯示受重金屬逆境植株在500-675 nm之黃綠光波段間反射率普遍增加，並在680-750 nm之紅光臨界區間會因為受重金屬逆境反射率普遍往短波長方向位移，產生紅光臨界藍移 (blue shift of red edge) 可做為植株是否受逆境之參考；氮素處裡效應較在100與200 ppm氮處理時較為顯著，其反射率會比氮濃度50 ppm處理組來得低，此外675 nm以上之波段中，各重金屬處理組合之反射光譜一次微分波峰質在高氮濃度下普遍往長波長方向位移，產生紅光臨界紅移 (red shift of red edge)。以常用波段或敏感波段計算之植生指數與植體重金屬濃度間建構線性及多項式模型，其中又以多項式模型較佳且具顯著相關性。因此利用反射光譜計算植生指數，非破壞性預估土壤有效性重金屬汙染物濃度與及植體累積重金屬含量，可能為有效可行之方法。

Consider that heavy metals can accumulate in plants and soil, and can be intake by people through feeding. To establish a proper monitoring system is necessary. Therefore, we would like to create indices using reflectance spectra to perform nod-destructive estimation the concentration of bioavailable heavy metal in soil and accumulation amount in shoot. In this research, hydroponic rice (Oryza sativa L. cv. Taichung Sen 10 and Taiken 9, TCS10 and TK9) seedlings were treated with treatment combinations of three nitrogen concentrations (50, 100, and 200 ppm) and three heavy metal concentrations (Cd: 0, 50, 100, and 200 µM; Cr: 0, 100, 200 and 500 µM; Pb: 0, 100, 200 and 500 µM) to simulate the effects of heavy metals in soil solution on rice seedlings under different nitrogen management in the field. The reflectance spectra of leaves were recorded and used to calculate vegetation indices to observe the relation between vegataiton indices and the heavy metal concentration in shoots. The result indicated that heavy metals stress inhibited shoot length of rice seedlings. At high metal concentration, the reflectivity in 500-675 nm of yellow and green light would increase and blue shift of red edge would happen at the same time. Additionally, for the treatment effect of high nitrogen concentration, the reflectivity in green light and red light would decreas, and red shift of red edge would happen at the same time. The linear and quadratic models were constructed from the relation between heavy metal concentration of shoot and vegetation indices. The results showed that quadratic models had better correlation. And the quadratic models are more suitable for TK9 than TCS10. Therefore, it appears to be possible to calculate indices using reflectance spectra for non-destructive estimation the concentration of bioavailable heavy metal in soil and accumulation amount in shoot.