以生物配位體模式評估鈣及鈉大豆幼苗吸收鎘之影響

Use of Biotic Ligand Model (BLM) for Assessing the Effects of Calcium and Potassium on Cadmium Uptake by Soybean Seedlings

楊慶明(Ching-Ming Yang) ； 何珮綺(Pei-Chi Ho) ； 游淳卉(Chun-Hui Yu) ； 莊愷瑋(Kai-Wei Juang)

《作物、環境與生物資訊》 10卷2期 (2013/06) Pp. 111-122

https://doi.org/10.30061/CEB.201306_10(2).0003

摘要

由於土壤溶液中的大量陽離子（如:Ca^2+、Mg^2+、K^+及Na^+等）可能干擾重金屬作用於植物根表面的毒性和吸收機制，因此單僅考慮溶液中重金屬濃度或離子活性並無法在不同土壤背景環境下，精確說明重金屬的植物毒性與有效性。本研究以陽離子競爭概念的生物配位體模式（biotic ligand model; BLM），探討說明溶液中鈣、鉀濃度對大豆幼苗吸收鎘的影響，以提供評估不同土壤環境背景下重金屬植物有效性和作物食用安全之參考。本研究以綠肥用青皮大豆[Glycine max(L.) Merr.]進行鎘累積試驗，將大豆幼苗植株分別曝露於不同鈣、鉀背景濃度之含鎘溶液，為期一週後採收植體並測定鎘吸收量。結果顯示，提高溶液鈣離子濃度能顯著降低大豆幼苗的鎘吸收量，但增加鉀離子濃度則無顯著影響。再以BLM套配試驗結果並求出各項模式參數，則可量化說明增加鈣離子濃度對減緩鎘吸收的作用，並準確推估不同鈣背景濃度下大豆幼苗的鎘吸收量。由此可見，依據BLM的陽離子競爭概念說明鈣、鎘離子間相互競爭植株根表面的吸收位置，可部分解釋大豆幼苗吸收鎘會受到溶液中鈣離子濃度干擾。本研究結果亦顯示，BLM相較於總濃度模式（total concentration model; TCM）和自由離子活性模式（free ion activity model; FIAM）更適於評估不同陽離子溶液背景對改善重金屬毒害植物之有效性。

關鍵字

重金屬 ； 生物配位體 ； 水耕試驗 ； 植物毒性 ； 植物有效性

並列摘要

The cations of macro elements in soil solution (e.g., Ca2^+, Mg^2+, K^+, and Na^+) will influence the toxicity and uptake mechanisms of heavy metals on plant root surface. Both soil characteristic background and heavy metal concentration (or activity) should be taken into account simultaneously for evaluation of phyto-toxicity and -availability of heavy metals. In this study, the biotic ligand model (BLM), which takes into account the macro element cations competition with heavy metal ions for biotic ligands on root surface, was used to illustrate the effects of calcium (Ca) and potassium (K) on cadmium (Cd) uptake by soybean seedlings. A hydroponic culture was carried out for one week to measure the change in Cd uptake by seedlings of soybean [Glycine max (L.) Merr.] under Cd exposures, with different concentrations of Ca and K in solution. Results showed that as Ca concentration increased to 2 mM, a significant decrease of Cd uptake by seedling could be observed, indicating that Ca reduced the uptake of Cd. However, there was not significant reduction in Cd uptake due to the increase of K in solution. By fitting the BLM to the rate of Cd uptake in soybean seedling with a function of Ca activity, the influence of Ca on the uptake of Cd was properly illustrated. The reliability of prediction of Cd uptake by soybean seedling was also validated under different Ca concentrations in solution. Implying by the competition concept of BLM, alleviation effects of Ca on Cd uptake may be referred to Ca^2+ competition with Cd^2+ for the biotic ligands (i.e., uptake sites) on root surface. Compared with the results from total concentration model (TCM) and free ion activity model (FIAM), BLM is superior to TCM and FIAM for assessing the availability of heavy metal in different solution backgrounds.

並列關鍵字

Heavy metal ； Biotic ligand ； Hydroponic culture ； Phyto-toxicity ； Phyto-availability