臭氧為一光化氧化物（Photochemical），屬二次污染物，具蔓延性，不論都會區、工業區或鄉村皆可發現其存在。臭氧於1950年代即被確認是極具植物毒性之重要空氣污染物之一，對農藝、園藝作物、草本植物及木本植物等均具植物毒性。本研究利用開頂式燻氣室（Open top chamber, OTC）進行臭氧燻氣試驗，探討臭氧對台灣地區常見草類之慢性為害情形。測試植物包活：菊科之咸豐草、紫花霍香薊、昭和草；禾本科之牛筋草、馬唐草、紅毛草；莧科之野莧、青莧及大戟科之飛揚草等9種田野常見草類，分別以60、80、120及200ppb等濃度進行二週之燻氣試驗。在60、80ppb臭氧之燻氣下，測試草類無徵狀出現，而植株之株高、葉片數目及乾物重等生育特徵與對照組無差異，在120ppb臭氧濃度下，馬唐草、咸豐草及紫花藿香薊等出現受害徵狀，於200ppb臭氧燻氣下，除紅毛草及昭和草之外，其他草類皆出現受害徵狀。燻氣試驗結果顯示，馬唐草、咸豐草、紫花藿香薊屬較敏感者，牛筋草、青莧及野莧次之，對臭氧具耐受能力者為昭和草、紅毛草及飛揚草。供試植物之抗壞血酸（ascorbic acid）、植物葉片萃取液之pH植、葉綠素含量、相對水分含量及Singh等所提出之空氣污染容忍指數（APTI, air pollution tolerant index）與臭氧所導致葉片受害無明顯關係。

Tropospheric ozone is a secondary pollutant widely exist around cities, industrial area and rural areas capable of causing plant injury and crop yield losses. In this study, we investigated the effects of ozone exposure on nine weeds common to lowland areas in Taiwan. Pot raised plants were fumigated seven hours(09:00-16:00) a day for two weeks with different level of O3(60-200ppb)in open top chambers. Data on injured leaf-area, plant height, leaf number and biomass was collected. No detectable difference was observed for plants receiving 60 or 80 ppb fumigation. Leaf injury appeared on Digitaria abscendens, Bidens pilosa and Ageratum houstonianun after ozone treatment of 120 ppb. Crassocephalum crepidioides and Rhynchelytrum repens showed no symptoms at 200 ppb level. Overall data suggested that Digitaria adscendens, Bidens pilosa and Ageratum houstonianun were the most sensitive species, followed by Eleusine indica, Amaranthus viridis and spleen Amaranthus patulus. Most tolerant species were Crassocephalum crepidioides, Rhynchelytrum repens and Chamaesyce hirta. Ascorbic acid, leaf-extract pH, total chlorophyll and relative water content of tested species were determined on non-fumigated plants. These parameters and the calculated air pollution tolerance index (APTI) were not closely related with their responses to ozone exposure.