Plant growth activity

Phenylacetic acid and its hydroxy isomers (ortho, meta, and para) have been isolated from many plants and microorganisms (82) and have been reported to have plant growth activity. 

Hoffman and Smith (1949a) reported in the plant growth activity of N-aryl-phthalamic acids. The only one used as a herbicide is N-l-naphthylphthalamic acid (naptalam, 33). 

Luan, L. Q., Nagasawa, N., Tamada, M. 2006. Enhancement of plant growth activity of irradiated chitosan by molecular weight fractionation. Radioisotopes 55 21-27. 

Figure 3 Sulfonylureas Tested Prior to Discovery of Plant Growth Activity...

The ideal plant growth regulator should leave no harmful persistent residue in a finished product or crop and the paradigm compounds are ones that have high specific activity, are target specific, and are environmentally biodegradable. 

Naphthalene Acetic Acid and Naphthalene Acetamide. Naphthalene acetic acid [26445-01-2] (38) is historicaHy one of the first plant growth regulators. Reports concerning its activity in crops and plants have been a subject in much of the eady Hterature (57). Consequently, it has been used as a starting matedal for other compounds, eg, vide infra Sevin. Naphthaleneacetamide [31093-43-3] (39) has been used as a standard matedal to evaluate abscission pnor to 1953 and its effect on apple drop was reported in 1953 (58). The substance is used as an internal standard in the abscission bioassay (59). 

The correlations between chemical descriptors of molecular properties and biological activity, especially the activity of herbicides and/or plant growth regulators has been described (12). Several alternatives or improvements on the Hansch-Fujita QSAR system have been developed (13—15). 

Naturally Occurring Compounds. Many derivatives of iadole are found ia plants and animals where they are derived from the amino acid tryptophan. Several of these have important biological function or activity. Serotonin [50-67-9] (12) functions as a neurotransmitter and vasoconstrictor (35). Melatonin [73-31-4] (13) production is controlled daily by the circadian cycle and its physiological level iafluences, and seasonal rhythms ia humans and other species (36). Indole-3-acetic acid [87-51-4] (14) is a plant growth stimulant used ia several horticultural appHcations (37). 

Eluorescent lamps for showing plants use a blue-white phosphor blended with a deep red-emitting phosphor. This more closely corresponds to the action spectmm for plant growth because there is Htfle green in the spectmm, African violets, for example, have leaves which appear more purple in color. The deep red emitter which is commonly used is magnesium fluorogermanate activated by Mn. ... 

C Hansch, RM Muir, T Fujita, PP Maloney, E Geiger, M Streich. The correlation of biological activity of plant growth regulators and chloromycetm derivatives with Hammett constants and partition coefficients. J Am Chem Soc 85 2817-2824, 1963. 

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