Changes in cell walls during fruit ripening in Chinese ‘Honey’ peach

Abstract

SummaryModifications in cell wall ultrastructure, cell wall polysaccharides, and the activities of some enzymes involved in cell wall degration were evaluated during the development and ripening of ‘Honey’ peach (Prunus persica L., ‘Yuhuasanhao’) fruit from Stage I (very immature) to Stage V (over-ripe). Ultrastructural changes in the mesocarp of peach fruit were followed over the same time-course. The results showed that the decrease in fruit firmness was accompanied by an increase in ethylene production during peach ripening. Major changes in cell wall structure were noted, beginning with degradation of the middle lamella and the eventual disruption of the primary cell wall. During peach fruit softening, the trans-1, 2-cyclohexane-diamine-N, N, N’, N’-tetra-acetate (CDTA)-1 fraction decreased slightly during the initial ripening stage, then increased rapidly, whereas the contents of all other cell wall materials (CWM), namely the CDTA-2, Na2CO3-1, Na2CO3-2, KOH-1, KOH-2, and CWM-residue fractions decreased gradually during ripening. An analysis of sugar components suggested that not only did the main chains of pectin degrade, but the arabinose and galactose residues in the side-chains of pectin, hemicellulose, or cellulose were also degraded. β-Galactosidase activity was high in immature peach fruit, then declined during peach ripening. However, the activity of α-L-arabinofuranosidase was low from Stage I to Stage III, then increased rapidly in the later Stages (IV – V). These results demonstrate the dynamic changes that occur in cell wall components, and in some cell wall-modifying enzymes during ‘Honey’ peach fruit development and ripening.