Higher plants biological control

The presence of catechols and more complex, oxidizable polyphenols in nature is widespread, and their functions are not limited to chemical defense. However, biological control of their oxidation is usually a feature of their function, as it is (1) in melanin synthesis,3 (2) in immunologically mediated delayed-type hypersensitivity responses,4 (3) in the hardening or curing of arthropod secretions (for example, as in the surface attachment adhesives of the barnacle and in tanning of the cuticle in insects),5 as well as (4) in defensive mechanisms in higher plants, particularly in the unleashing of immediate necrotrophic responses.6... 

Most fungicides developed for plant disease control before 1965 are multisite biochemical inhibitors that lack the chemical properties and biological specificity required for internal therapeutic action in higher plants. This group of plant protectants include such compounds as the Inorganic copper fungicides, captan, chlorothalonil, dithiocarbamates and chlorinated quinones. 

The reduction of nitrate to ammonia is a rather simple chemical process under very complex control in biological systems. In higher plants the assimilation of nitrate involves the acquisition and subsequent reduction of nitrate to ammonia by nitrate and nitrite reductase. Although our understanding of the biochemistry, genetics, and molecular aspects of nitrate assimilation has advanced, a great deal remains to be learned, especially about regulation and... 

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