本研究利用植株生長勢，葉綠素螢光反應，及植體藥劑殘留量測定，探討非致死劑量之二、四─地，對玉米及胡瓜之毒性，及免疫分析在藥害診斷技術之可利用範圍。二、四─地萌後噴施於2-3 葉之胡瓜及玉米植株，定期調查植株藥害徵狀，株高、葉數、鮮重等生育性狀，及葉片葉綠素螢光變化，並配合植體殘留量之檢測。以240 g ha-1 劑量噴施玉米植株，未造成明顯的外觀形態異常，及生育抑制現象；藥劑殘留量於噴後四小時測得7.64 ± 0.51 μg gfwt -1，三日後消退至3.95 ± 0.21 μg g fwt -1，15 日後仍可測得0.74 ± 0.06 μg gfwt -1 為對照株的6.2 倍，三星期左右兩者測值相近。以120 g ha-1 劑量施用於胡瓜，主要造成噴施時已展開之第二葉萎凋，及正在發育之第三葉皺縮；施藥後15 日之植株外觀受損達20%，株高、葉數、鮮重等生育降至對照株之40-78%；第二及第三葉片之葉綠素螢光：Fo 值升高，Fv/Fm 及Fm/Fo 值變化較小。施藥後30 日植株生長有恢復趨勢，但株高及鮮重仍較對照為差。植體內藥劑殘留量，噴後四小時測得6.61± 0.23 μg gfwt -1，15 日後降為2.61 ± 0.11 μg gfwt -1，30 日後仍可測得對照之3.91 倍。免疫分析具有之高靈敏度偵測特性，對外觀徵狀不明顯之藥害診斷，提供了直接的輔助性證據。

2,4-D is commonly used for weed control of sugarcane in Taiwan. Sprayingunder unfavorable field conditions often resulted in drifting and injury of crops infarmland bordering the plantation. Simple and sensitive methods for detecting ofresponsible agent are very useful in the diagnosis of phytotoxicity of non-targetplants. In this study, we used immunochemical assay for the quantitative detectionof 2,4-D in corn and cucumber. Characteristic symptoms, agronomic parameters,and changes of chlorophyll fluorescence were also investigated. Sub-lethal levelof 2,4-D was sprayed over-top to potted plants at 2-3 leaf stage. Symptomsappeared on the youngest fully-expended leaves of cucumber after 2,4-D sprayingwith 120 g ha-1. At this rate, 2,4-D resulted in 22-60% of phytotoxicity oncucumber at 15 days after application, and changes on the chlorophyllfluorescence of cucumber leaves with a slight increase in Fo values and reductionin Fv/Fm and Fm/Fo values. Corn was lightly injured by 240 g ha-1 of 2,4-Dand recovered growth rapidly. At 15 days after application, 0.74 ± 0.06 μg gfwt -1of 2,4-D was detected in corn. And residue detection in cucumber was 1.25 ± 0.07μg gfwt -1 at 30 days after application. The sensitive and specific immunoassayprovided additional information on proper diagnosis of 2,4-D injury to crops.