本研究以12種雜草、4種作物、及3種藤類植物為材料，比較這些植物對除草劑嘉磷塞[glyphosate,N-(phosphonomethyl)glycine]的忍受性與EPSPS(5-enolpyruvylshikimate-3-phosphate synthase,EC 2.5.1.19)活性的關係。以嘉磷塞溶液噴施這些植物的葉面，大部份植物皆受到相當嚴重的藥害，最常見的徵狀是葉片黃化、萎凋及壞疽，使植株乾、鮮重生長及葉綠素含量減少。但山萵苣(Lactuca indica)、細梗絡石(Trachelospermum gracilipes)、三葉崖爬藤(Tetrastigma formosana)及波緣竹仔菜(Commelina undulata)等4種植物的忍受性較高，葉片雖然受到部分藥害，植株並未死亡。由分離葉綠體所測得的EPSPS活性結果，顯示不同植物種類間具有相當大的差異，活性最低之加拿大蓬(Erigeron canadensis)只有44.3pkat mg-1 chl.，活性最高之短葉水蜈蚣(Kyllinga brevifolia)達634.9pkat mg-1 ch1.，兩者相差達14倍。上述4種忍受性較高的植物其EPSPS活性介於107.3至237.2pkat mg-1 chl.，並不比其他藥害更嚴重的植物為高。換言之，自然界正常生長的植物對嘉磷塞的忍受性與其EPSPS活性的高低無關，可能的原因在本研究中亦加以討論。

The purpose of this study was to compare the tolerance of plants including 12 weed species, 4 crops and 3 climbing vines to glyphosate[N-(phosphonomethyl)glycine] in relation to their EPSPS (5-enolpyruvylshikimate 3-phosphate synthase, EC 2.5.1.19)activity.Glyphosate caused phytotoxic injury on al the plant species tested. Common symptoms were leaf yellowing wilting follwed by necrosis.Plant fresh weight,plant dry weight, and chlorophyll content decreased significantly within 10 days after foliar spraying. However, some plant species such as Lactuca indica, Trachelospermum grocilipes, Tetrastigma formosana, Commelina undulata were relatively tolerant. The EPSPS activity assayed from isolated chloroplasts was different amon plant species, from as low as 44.3 pkat mg chl. of Canada thisthle (Erigeron canadensis) to as high as 634.9 pkat mg chl. of Kyllinga brevifolia. The activity of the four relatively tolerant plant species was between 107.3 to 237.2 pkat mg chl. This sugested that the level of EPSPS activity in plants grown under normal condition was not closely related to glyphosate tolerance. Some possible interpretations are discussed.