Prior to phytotoxic action, herbicide must be absorbed by the plant and reach its site of action, usually located within an organelle in the plant cell.

• 50 %25的除草剂主要是影响光合作用光反应之电子传递，其馀则分别为抑制胺基酸的生合成、干扰细胞正常分裂或具有植物生长素活性等；