This publication is based on the plant processes and reaction sites for which reliable knowledge on both their physiology and biochem-istry and the mode of herbicidal action is available. Targets of the agrochemical research, such as enzymes of biosynthetic pathways or herbicide-binding peptides in the photosynthetic membrane, are highlighted. Detailed knowledge about the target sites will allow bio-chemical model systems to evaluate the biological activity of newly synthesized compounds before their conventional screening in the greenhouse. Quantitative structure/activity relationships should be performed more reliably with simple biological species or enzymol-ogy assays, to aid in the rational design of pesticides. This text is highly valuable for plant physiologists, pathologists, and chemists in the agrochemical industry and universities.

Since the middle of the Sixties, new types of formulation for biologically active com pounds have been developed, which have been introduced into the literature under the term Controlled Release Formulations (CRF). Stimulated by results from former and successful pharmaceutical research, which was engaged in the production of prepa rations with protracted effects (introduction onto the market in the year 1952 of D amphetamine in the form of pellets, coated to varying degrees with fats and waxes) 1), experiments were carried out to transfer the prolongation of effectiveness to pesticidal substances also, by means of a depot formulation. Initial work was concerned with the production of protective coatings for sonar systems in marine ecosystems. By means of antifouling paints or rubber coatings containing tri-n-butyl-tin oxide (TBTO), the growth of marine organisms on sonar domes, buoys and hulls in the water could be effectively prevented 2. 3). Controlled release formUlations of pesticides are defined as depot systems which continuously release their toxic constituents into the environment over a specified period of time (usually months to years) 4). According to this definition, such formu lations can be successfully employed where a chronic exposure to biologically active compounds is required over a longer period. The following hypothetical example is intended to illustrate this 5). In Fig. 1, the duration of activity of a non-persistent pesticide with a loss rate under environmental conditions of t1/2 = 15 days, is graphically illustrated."