Cell wall changes in kiwifruit following postharvest ethylene treatment.
Redgwell, R. J.; Melton, L. D.; Brasch, D. J.;
Phytochemistry Year: 1990 Vol: 29 Issue: 2 Pages: 399-407 Ref: 14 ref.
1990
บทคัดย่อ
The compositions of the cell walls from four tissue zones of kiwifruit at three times after harvest were investigated. Cell wall breakdown triggered by ethylene did not occur simultaneously in different tissue zones of kiwifruit, being more pronounced in the outer pericarp and inner pericarp but much less in the locule wall and core tissues. Cell wall material (CWM) from the outer pericarp lost 80 and 64% of the CDTA (cyclohexanediamine tetraacetic acid)- and sodium carbonate-soluble fractions, respectively. However, the remainder of these fractions in the CWM of ripe fruit contained higher proportions of galactose, arabinose and rhamnose than did fruit at harvest. These sugars occur at branchpoints or in sidechains in kiwifruit pectic polymers; a fact that pointed to a non-random degradation of the wall polysaccharides and the preferential release of the less-branched parts of the rhamnogalacturonan backbone of the pectic substances. There was a 50% decrease in outer pericarp cell wall galactose, 80% of which occurred in the KOH-soluble and CWM residue fractions. Comparison of whole kiwifruit at harvest and seven days after ethylene treatment showed a net decrease in galactose (33%) and arabinose (22%). Absence of sufficient free galactose or galactose-containing oligosaccharides to account for the galactose released from the wall polysaccharides during ripening, implied postharvest metabolism of cell-wall-derived galactose. In contrast, the uronic acid in the cell wall was partially converted to soluble forms during ripening without any apparent loss due to metabolism.