Utjecaj metabolizma stanične stijenke na dozrijevanje plodova voća Ziziphus mauritiana

Two ber varieties differing in their shelf lives (Umran, 8 to 9 and Illaichi, 4 to 5 days) were analyzed for cell wall components, cell wall degrading enzymes and their isoenzyme profile at immature green, mature green, turning colour, ripe and overripe stages of ripening. Cellulose and pectin contents decreased during ripening in both varieties. This decrease was accompanied by a corresponding increase in pectin methylesterase, polygalacturonase and cellulase. The increase in the activity of pectin methylesterase was about 20- and 10-fold, that of polygalacturonase about 8.4- and 5.7-fold, and of cellulase 5.5- and 4.4-fold in Umran and Illaichi, respectively. The basal level of activities of all these enzymes was higher at all the stages of ripening in Illaichi variety, having short shelf life, as compared to Umran, with long shelf life. This was further confirmed by the intensity of isoenzyme bands of these enzymes. The isoenzyme profile also revealed that two isoenzymes of each, pectin methylesterase and polygalacturonase, and one of cellulase could be considered as isoenzymes responsible for the softening of cell wall during ripening and could be potential targets for manipulation to delay softening during ripening.U radu su ispitane dvije sorte voća Ziziphus mauritiana koje se razlikuju prema roku trajanja, i to sorta Umran (roka trajanja od 8 do 9 dana) i sorta Illaichi (roka trajanja od 4 do 5 dana). Analizirani su sastojci stanične stijenke, enzimi koji ju razgrađuju te njihovi izoenzimi u nezrelim zelenim, dozrelim zelenim plodovima i onima koji su promijenili boju, te u zrelim i prezrelim plodovima. Udjel se celuloze i pektina smanjivao tijekom dozrijevanja u obje sorte, što je uzrokovalo povećanje udjela pektin metilesteraze (u sorti Umran 20 puta, a u sorti Illaichi 10 puta), poligalakturonaze (8,4 i 5,7 puta) i celulaze (5,5 i 4,4 puta). U svim su fazama dozrijevanja voća osnovne aktivnosti tih enzima bile izraženije u sorti Illaichi, što potvrđuje i intenzitet njihovih izoenzimskih vrpci. Iz izoenzimskog je profila pektin metilesteraze, poligalakturonaze i celulaze vidljivo da ti enzimi razgrađuju staničnu stijenku tijekom dozrijevanja plodova, te da se njihovom inaktivacijom taj proces može usporiti