DEVELOPMENTAL AND RIPENING-RELATED EFFECTS ON THE CELL-WALL OF APRICOT (PRUNUS-ARMENIACA) FRUIT

Alcohol-insoluble residues (AIRs) were prepared from apricots at six s tages during development/ripening on the tree. To investigate the chan ges in cell wall polymers, and in particular those affecting pectic po lysaccharides, the AIR preparations were sequentially extracted with w ater, clohexane-trans-1,2-diamine-N,N,N',N'-tetraacetate (CDTA) and Na 2CO3. A significant proportion of initially Na2CO3-soluble pectic poly saccharides became water- and CDTA-soluble during the ripening process . In terms of composition, a significant decrease in galactose and uro nic add content was detected in all the extractions, whereas the perce ntage of arabinose increased in both water and CDTA-soluble polymers b ut decreased in the Na2CO3-extracted polysaccharides. The ability of p ectic polysaccharides to cross-link was diminished during ripening due to an overall increase in the concentration of Na+ or K+ associated w ith the AIRs. This was accompanied by a decrease in the amounts of Ca2 + and Mg2+. The decrease in pectic galactans and the inhibition of pec tin cross-linking detected within the pectic backbone are probably lin ked to the softening process observed during apricot ripening. (C) 199 8 SCI.