ABSTRACT
This chapter describes the mechanisms of absorption and translocation of preemergence and postemergence applied herbicides. It discusses the involvement of absorption and translocation in plant tolerance to herbicides. Absorption of soil-applied herbicides can occur in root and shoot tissue in direct contact with herbicide dissolved in the soil solution or present in the vapor phase. During germination and growth, prior to soil emergence, shoot tissue is exposed to the soil solution and any herbicide dissolved in the soil solution. The most significant barrier to herbicide absorption into shoot tissue is the cuticle, which covers the surface of essentially all epidermal cells of all above-ground shoot systems. The cuticle is a complex and variable layer. With the exception of herbicides that may act at the plasmalemma surface, herbicides must move across the plasmalemma prior to reaching the site of action. Several methods are used to determine herbicide translocation. Most commonly, translocation is determined by autoradiography of plants treated with radioactive herbicide.
