巴拉刈(paraquat)是目前全球使用最多之非選擇性除草劑之一，主要作用機制是抑制植物光合作用光系統Ⅰ(photosystem Ⅰ)之電子傳遞，同時因取得電子後促使產生活化氧族，形成氧化逆境，其對於雜草防除效果相當快速。巴拉刈因長期使用造成雜草產生抗性，本研究乃綜合相關研究報告，將可能存在之抗性機制歸類，包括巴拉刈之吸收、轉運、代謝、以及在植物體內產生活化氧族後之抗氧化防禦機制加以說明及討論。

Paraquat (1, 1'-dimethyl-4, 4'-bipyridylium) is a non-selective herbicide widely used in the world more than 35 years. The action mechanism of this herbicide to kill plants is an inhibition of electron transport in photosystem Ⅰ, which also results in the formation of oxidative stress environment due to a large production of reactive oxygen species. Since the long-term application of paraquat, herbicide resistance in weed plants has been reported and paid more attentions. In this article, physiological mechanisms of paraquat resistance commonly found in weed plants and microbes, including uptake, translocation, and metabolism of paraquat, as well as antioxidative system to remove free radicals generated by paraquat radical, are reviewed and discussed.