Growth regulatory hormones

Mention should be made of abscisic acid and related compounds. Abscisic acid (373) was first isolated from young cotton fruit as an abscission-accelerating principle. It has since been found to be ubiquitous in higher plants and has been detected in the roots of several plants. It is now recognized as a natural plant growth regulatory hormone. Although structure 373 is clearly that of a monocyclofarnesane and could arise from cyclization of FPP and further modification, there is some evidence that it may be a catabolic product of a carotenoid, such as violaxanthin. Considerable biosynthetic work has been carried out, but no clear-cut answer is available yet (110, 179, 276). 

An excess of insulin can cause hypoglycaemia and the hormones that respond to this condition to restore normal glucose levels are known as the counter-regulatory hormones. They are adrenaline, glucagon, growth hormone and cortisol. An increase in the blood levels of these hormones can sometimes be used to conhrm a diagnosis of hypoglycaemia. 

TRH = thyrotropin regulatory hormone PIF = prolactin inhibitory factor GnRH = gonadotropin regulatory hormone IGF-1 = insulinlike growth factor 1 ACTH = corticotropin GH = growth hormone TSH = thyrotropin Prl = prolactin... 

There are many naturally occurring compounds that have plant growth regulatory effects in whole plants or bioassays, and brassinosteroids are certainly potent - but should they have plant hormone status ... 

---