Giberellic acid

A large number of studies (33) support the thesis (59) that the function of GA may be that of a derepressor of gene activity. Giberellic acid has significant effect on the synthesis of all species of RNA s (63, 64), but the formation of < —amylase does not depend on new synthesis of ribosomal and transfer RNA s. Unequivocal proof for GA-induced formation of transcripts was provided by the in vitro synthesis of peptides that are immuno-logically similar to -amylase on poly A+RNA templates that were. isolated from hormone-treated aleurone cells (65, 66, 67). Of particular significance is the finding that detectable levels of -amylase mRNA s were formed within 2 hr of treatment with GA. 

Corey, E.J. et al . 1978, Stereospecific synthesis of giberellic acid , Journal of the American Chemical Society, 100, 8034-6. 

Terpenoids are also used as chemical messengers. If the communication is between different parts of the same organism, the messenger is referred to as a hormone. Examples of hormones are shown in Figure 1.8. Giberellic acid is a hormone used by plants to control their rate of growth. Testosterone and oestrone are mammalian sex hormones. Testosterone is a male hormone and oestrone, a female. 

The kaurans present in M. tomentosa and M. frutescens have been extensively studied. This chemical group is relatively abundant in nature and arises by simple oxidation and/or epoxidation and hydrolysis reactions. They are precursors of giberellic acid and therefore have demonstrated activity as plant regulators [35]. The kaurenes have uterotonic and uterorelaxant effects but also display a wide spectrum of antimicrobial and fungicidal activities especially kauren-19-oic acid. Grandiflorenic acid (Kauradienoic acid, GA) is weakly active against Bacillus subtilis, and the methyl ester compounds appear to be less active [35]. 

The allylic oxidation with f-butyl hydroperoxide and catalytic selenium dioxide was used in the synthesis of a giberellic acid (Eq. 67).187 authors state that the reaction is inefficient under standard conditions. 

H. S. Salama and A. M. El-Sharaby, Giberellic acid and jS-sitosterol as sterilants of the cotton leaf worm Spodoptera littoralis Boisduval, Experientia 28, 413-414 (1972). 

Terpenoids are also used as hormones. In mammals, the role of steroids is vital and will be discussed in the article on steroids. The diterpenoid giberellic acid [77-06-5] (14) is a plant growth hormone. 

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