草殺淨（ametryn）為本省蔗田常用之萌後除草劑，但常因使用不當，使藥滴飄造（drift）造成非目標區作物產生藥害。本研究探討草殺淨之萌後處理引起作物產生藥害之情形、作物對藥劑之反應以及葉綠素螢光變化偵測草殺淨之藥害。以推薦用於蔗田之使用劑量（1.6 kg/ha）的1/4、1/16、1/32、1/64、1/256等劑量之草殺淨，噴施於胡瓜及玉米植株；胡瓜在1/4推薦劑量處理後，植株急速的褐化，在五天內全部枯死。以1/256推薦劑量噴施，胡瓜藥害在10天左右達30%之褐化枯萎程度。玉米僅在施用達1/4推薦劑量時發生輕微的黃化、藥斑；較低之劑量，則無明顯可則之藥害徵狀。隨著噴施劑量之降低，植株受到傷害之程度減輕，最早發生藥害徵狀的時間延長且速度亦減緩。其他各種作物對於草殺淨有不同之反應，表現於藥害發生之時間、外觀徵狀及植株受藥劑傷害之程度亦有差異。草殺淨屬三氮雜苯（triazine）之除草劑，其主要的作用機制為阻礙光合作之電子傳送，使植株呈現異常的螢光反應。利用葉綠素螢光測定儀，在植株進行30分鐘暗反應後，測定胡瓜及玉米植株之各螢光介量參數值之變化，發現隨著施用劑量之增加，Fo值隨之上，而Fv/Fm、Fm/Fo值卻下降，螢光釋放曲線圖中之Fi螢光差值減小且停滯期縮短，Ac與對照組相比較之下亦減少。試驗結果顯示，植株外部藥害徵狀未明顯出現時，可由螢光測定值顯示出其受藥劑劑量之影響。

Ametryn is the most important herbicide for sugarcane in Taiwan. Major problem of this chemical is crop injury off the target area caused by drifting. We investigated ametryn-induced phytotoxicity of non-target crops; Characteristic symptoms, dose-reponse relationship, and changes of chlorophyll fluorescence were studied. Ametryn at 1/4,1/16, 1/31, 1/64, and 1/256 of the rate that recommende for sugarcane (1.6 kg/ha) were used. Designated rates were applied on eggplant, tomato ,radish, cabbage, pea , snapbean, melon and watermelon of 2-3 week old. At 1/4 X rate, cucumber leaves were severely burned shortly after spraying and died down within five days; With 1/256 X rate. up to 30% of leaves was damaged at 10 days after treatment. Corn was lightly in jured by 1/4 X rate of ametryn, and phytotoxic symptoms developed slowly; With lower rate,detectable symptoms were less obvious. On other tested crops, ametry-induced phytotoxicity were different in dvelopment of symptoms and degree of damages. Changes on the fluorescence of crop samples were detected by a fluorimeter after a 30-minutes pre-treatment in darkness. Elevated rate resulted in higher initial fluoresccnce(Fo) but lower Fv/Fm, Fm/Fo and Ac. Ametryne-treated plants also associated with lower Ac and Fi values as well as shorter leveled duration of Fi. Measurement of chlorophyll fluorescence provided additional information on crop susceptibility to ametryne besides visual symptoms.