Proceedings Volume 2010 (format .pdf) - SimpBTH

Regarding superior plants they are taken into consideration the mainhormonal groups: auxins, gibberellins, citokinine, abscisic acid and ethylene.Auxins, gibberellins and citokinine are growth promoters and the abscisic acid andthe ethylene are growth inhibitors.During the plant evolution, if phytoromones stimulate the growth processand retardants stop it, inhibitors stop it completely or partially. Controlling theplant evolution mechanism by inhibiting the biochemical processes at the rightmoment can lead to obtaining vegetal products at the desired quality.Phytohormones with inhibiting properties can operate on the whole plant as well ason some tissues and organs causing the inhibition of some metabolic processeslike: biosynthesis of nucleic acids, photosynthesis of chloroplasts and of somephysiological processes, especially the division and elongation of cells and thebuds opening. [12]The abscisic acid is an inhibitor acid and alongside growth stimulatingsubstances: auxins, gibberellins, citokinine controls the processes of plant growthand development. It is the promoter and it maintains the ageing process by hastingthe fruit and leaves abscission. That is why it is called abscisic acid (theinternational abbreviation is ABA). [2, 5]Ethylene has a large specter of biochemical and physiological action over thegrowth process of plants. It is the first gaseous hormone and it is also known as thehormone of fruit ripening. [2, 6]The authors of this paper want to distinguish the mechanisms through whichphytohormones with inhibiting properties operate on the plant evolution processesas well as the influence they have on the course of their action.2. RESULTS AND DISCUSSIONChemically speaking, the abscisic acid is a sesquiterpene because itconsists of three isoprene units. It is composed of a (iononic) hexacycle and alateral catena that has 5 carbon atoms with two double conjugated bounds. ABAcontains an asymmetrical carbon atom (C -1) and that is why it forms 2 opticenantiomers (endogenous ABA is dextrogir). The double bound in the nucleus ofthe hexacycle determines two isomers to form: cis and trans. [8, 9]In figure 1 there are presented the structures of the two geometric isomersof the abscisic acid.39