Regulation, hormone remote

Phytohorntones, plant hormones The classic P. are endogenous regulators of plant growth and development. They are analogous to animal hormones in that the sites of their synthesis may be remote from the sites of their action, but in contrast to animal hormones, P. have multiple activities and low action specificities. Oligosaccbarins (see), however, are much more specific and are elective at concentrations similar to those at which animal hormones are effective (10- -10" M), but they may not be transported from their site of synthesis to the site of their action. 

The simple model of a hormone system implies that the chemical species will induce the regulatory response in some place remote from the site of its synthesis. This model is extremely well adapted to the auxin regulation of coleoptile growth where the indoleacetic acid was found to be produced in the coleoptile tip and moved in a directional transport system to the elongating portion of the coleoptile where it stimulated growth. 

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