超低量巴拉刈（paraquat）在胡瓜及玉米植株之殘留及藥害診斷

Effect of an ultra-low rate of paraquat application on corn and cucumber: phytotoxicity and residue detection

探討利用免疫分析法檢測植體巴拉刈（paraquat）殘留量，做為藥液飄散引起作物藥害之診斷依據與適用範圍。巴拉刈以1.2g ha^（-1）超低劑量後噴施於2-3葉齡之胡瓜及玉米植株，定期調查植株藥害發生程度，株高、葉數、鮮重等生育性狀，及葉片葉綠素螢光變化，並配合免疫分析法檢測植體樣品之巴拉刈殘留量。巴拉刈處理胡瓜植株3日後，藥害發生率為15%，6日後達25%，18日後降至11%；玉米在6-12日期間之藥害亦超過10%，且6日後傷害最大（15%）；株高、葉數及鮮重等生育指標，以鮮重反應對藥劑較敏感，胡瓜及米分別在噴藥後6-15日及6-9日，其鮮重抑制率均高於10%，但以胡瓜反應較為明顯。兩種測試作物之葉片葉綠素螢光異常反應，胡瓜則較玉米明顯，但差異範圍在5%內。植體巴拉刈殘留偵測顯示；玉米及胡瓜植株之藥劑消失速率有差別；施藥後30日，以免疫分析法仍可測得胡瓜及玉米植株殘留有11.01及5.07ηg（g fwt）^（-1）之巴拉刈。免疫分析可檢測之藥劑殘留日數較長，鮮重抑制反應則持續表現至9-15日，兩者配合藥害徵狀，可提供作物微量接觸巴拉刈後約30日之藥害診斷依據。

"Paraquat is a widely used herbicide for controlling upland weeds in Taiwan. Spraying under unfavorable field conditions often results in drift and injury to crops in adjacent farmland. Simple and sensitive methods for detecting responsible agents are very useful in the diagnosis of phytotoxicity of non-target plants. In this study, we detected paraquat residues in corn and cucumber by immunoassay. Paraquat was sprayed over the top of potted plants at the 2- to 3-leaf stage at a rate of 1.2 g ha^(-1). Characteristic symptoms, agronomic parameters, and changes in chlorophyll fluorescence were also investigated. Paraquat-treated plants showed localized necrotic spots on cucumber and corn leaves. Phytotoxicity of paraquat treatment at 1.2 g ha^(-1) on cucumber and corn was observed at 3-18 and 6-12 days after application, respectively. There was a ＞10 % of reduction in fresh weight of treated crops at 6-15 and 6 - 9 days after application for corn and cucumber, respectively. Paraquat-treated plants resulted in higher initial fluorescence (F_0) but lower Fv/Fm. However, these changes were not significant. At 30 days after application, 11.01 and 5.07 ηg (g fwt)^(-1) of paraquat could be still detected using this immunoassay on cucumber and corn, respectively. The immunoassay provides a longer detection period and additional information on the diagnosis of paraquat in addition to visual symptoms."