CHARACTERIZATION OF THE CELL-WALLS OF LOQUAT (ERIOBOTRYA-JAPONICA L.)FRUIT TISSUES

Loquat fruit (Eriobotrya japonica L. cv. Algor) was dissected to give the following tissue zones: epidermis or epicarp, flesh or mesocarp, i ntegument (a thin layer surrounding thr: seed cotyledons), seed testa, kernel and hairy receptacle. The alcohol insoluble residues (AIRs) fr om all these tissues were proved to be free of starch, except loquat k ernel which on a fresh weight basis contained about 34% of starch. AIR s were analysed for moisture, ashes, protein, lignin and the component sugars were released by two hydrolytic procedures which helped to dis tinguish the sugars from non-cellulosic polysaccharides and cellulose. Their major component polysaccharides were inferred to be pectic poly saccharides since all AIRs were very rich in sugars such as uronic aci ds, arabinose and galactose. Pectic polysaccharides contributed up to 70% of total cell wall polysaccharides in the edible flesh of the loqu at fruit. Important differences in the degree of branching, degree of esterification and in the amounts of Ca and Mg associated with pectic polysaccharides were detected among pectic polymers depending on the l oquat tissue zone. These compositional and structural differences may be related to the role that these pectic polymers play within the tiss ues which form the loquat fruit. (C) 1998 Elsevier Science Ltd. All ri ghts reserved.