Plant growth modification and regulation

GROWTH REGULATOR (Plant). See Plant Growth Modification and Regulation. 

This paper traces in some detail the path which led to the discovery of a new class of herbicides, the 2-(5-oxo-2-imidazolin-2-yl)arylcarboxylates. The journey started when it was found that a phthalimide, a-isopropyl-a-methyl-l,3-dioxo-2-isoindoline-acetamide, had sufficient herbicidal activity to warrant further synthesis effort. This work led to a series of analogs essentially devoid of herbicidal activity yet possessing interesting plant growth regulating effects. Further chemical modifications resulted in the synthesis of two new groups of compounds, imidazoisoindolediones and dihydro-imidazoisoindolediones, and the return of herbicidal activity. The imidazoisoindolediones were in turn transformed into o-(5-oxo-imidazo-lin-2-yl)benzoates, the first members of a very interesting new class of herbicides. 

This term covers a broader spectrum of effects on plants than the term "plant growth regulators" that has been commonly used in English-speaking countries. This new definition should do greater justice to the variety of effects that are expected from this class of substances. These include not only an influence on the growth and development processes of crop plants or their specific organs, but also the modification of metabolic processes or the formation of certain constituents, as well as a modified stress behavior. 

Plant growth regulators have a remarkable influence on the production of benzyliso-quinoline alkaloids in some cultures. Fukui et al. (1982) described an increase of alkaloid yields by addition of kinetin or benzylaminopurine (0.1—1.0 pM). He also could observe a modification in the alkaloid pattern with higher concentrations (10 pM) of these phytohormones The production of palmatine and jatrorrhizine significantly decreased whereas berberine and coptisine formation remained largely uneffected. 

A number of plant sterols have been reported to possess growth-regulating activity and developmental modification properties in plants (Heftman, 1975a, 1975b, Mandava, 1979). For example, -sitosterol (4) initiates flower buds in Chrysanthemum species exogenously applied lanosterol (15) (not a plant product) also stimulates flowering in these plants. Estrone (oestrone) (21) and related compounds are... 

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