拉刈(paraquat)為台灣旱地作物田普遍用之殺草劑。目前已在田間發現野塘蒿(Erigeron sumatrensis)之抗性生物型，無法以推薦量的巴拉刈來防治。本研究的主要目的是以葉面積及莖、葉乾重對巴拉刈的反應，篩選出抗性生物型植株。同時比較抗感生物在巴拉刈處理後，對其光合作用抑制程度的差異情形。巴拉刈對抗感植株之葉面積、葉乾重反莖乾重的50%抑制劑量(I50)之R/S比值，依次為40,56及50；植株致死劑量之R/S比值亦大於50。而對葉片二氧化碳交換速率在巴拉刈處理三小時內會有顯著的影響；但對葉綠素、類胡蘿蔔素及可溶性蛋白質含量的影響則需較長處理時間；在抗性生物型內無論是光合作用或色素含量，均對較拉刈具有較大的容忍範圍。抗感葉片之蛋白質電泳分析圖譜的型式(pattern)相近似，只是條帶(band)的深淺有部份差異。

Paraquat is one of the commonly used herbicides in upland field of Taiwan. A biotype of upland weed Erigeron sumatrensis has been found which normally is not controlled by recommended rate of paraquat at any stage of growth. The lethal dosage for the resistant biotype is 1O,OOOppm which is 50 times greater than for the normal susceptible biotype (200ppm). After paraquat application at 25-30 leaf stages, the resistant biotype plant of E. sumatrensis exhibited high leaf area, leaf and shoot dry weight than susceptible biotype. Both biotypes showed growth inhibition after paraquat treatment, but with more accelerated decline in susceptible biotype. The resistant biotype was characterized with localized damage and able to regrow. Carbon dioxide exchange rate decreased sharply in plants after paraquat treatment, but the inhibition was more serious in susceptible biotype than resistant one. Contents of chlorophyll, carotenoid or protein was also reduced by paraquat application, but it took longer time to show changes of these parameters than that of CO2 exchange. In lD SDS 司 dimensional gel electrophoretic analysis of leaf protein demostrated that the patterns of two biotypes did not have markedly difference.