PHENOLIC-ACIDS AND PEROXIDASE-ACTIVITY IN ALFALFA (MEDICAGO-SATIVA) EMBRYOGENIC CULTURES AFTER ETHEPHON TREATMENT

Treatment with ethephon increased the concentration of exogenous ethyl ene in Medicago sativa L. embryogenic cell suspension cultures (consis ting of single cells, small cellular clumps and globular somatic embry os) and induced changes in the metabolism of phenolic substances, acti vities of peroxidase (EC 1.11.1.7) and caused significant suppression of suspension culture growth. Treatment with the ethylene-releasing su bstance, ethephon, resulted in a several-fold increase in phenylalanin e ammonia-lyase (PAL; EC 4.3.1.5) activity above the basal level and w as accompanied by an elevated accumulation of phenolic acids (signific ant increase of methoxy-substituted acids). The majority of newly synt hesised phenolic acids was incorporated into the fractions of glycosid es and esters bound to the cell wall. Phenolic glycosides seemed to se rve as a metabolic pool from which the phenolics were utilised during further culture. The increased activity of wall-bound ionic peroxidase after ethephon application correlated with the pronounced incorporati on of ferulic acid in the cell walls. In contrast, the increased level of exogenous ethylene did not influence the growth of culture of more advanced embryos nor did it significantly alter phenylpropanoid metab olism.