Proceedings Volume 2010 (format .pdf) - SimpBTH

Fig.1. The structures of the two geometric isomers of the abscisic acid.The biosynthesis of ABA takes place in chloroplasts, through the generalpath of the synthesis of terpenoidic compounds and through the photooxidation ofsome carotenoids.The catabolism of ABA is similar to the one of carotenoidic pigments andtriterpenic derivatives. Under the action of some specific enzymes (oxidase,lipooxidase, peroxidase) the abscisic acid suffers oxidative changes which can takeplace at the hexacycle’s level. The path of the biosynthesis of abscisic acid and themajority enzymes involved were identified (Fig. 2). [13]The molecular action mechanism of ABA in vegetal organism is not fullyelucidated. It is known that ABA has a biochemical and physiological action againstsubstances that stimulate growth, forming a biochemical “balance” that causes theplant to grow and develop in different phenophases and seasons in the temperatezones.The inhibition of the growth and development of plants takes place becausethe biosynthesis of the ribonucleic acids inhibit, especially the RNAm blocking theprocesses of transcription and translation of information from the DNA’smolecule. The proteins biosynthesis is blocked (enzymes). The processes ofphotosynthesis, breathe, oxidative phosphorilation are reduced. [3]Another biochemical action mechanism of ABA in plants is the flux ofinorganic ions adjustment through the biological membrane. This mechanism ispresent in leaves, in the cells that cause the stoma to close and open by regulatingthe content of K +.40