Histological and physiological characterization of rind breakdown of 'Navelate' sweet orange

Rind breakdown of 'Navelate' sweet orange is characterized by sunken colour less areas of the peel which develop into reddish-brown, dry areas partiall y covering the exposed portion of the mature fruit. Sudden changes in relat ive humidity at fruit colour break seem to be responsible for the natural d evelopment of this disorder, which begins at the transitional zone of the f lavedo-albedo and advances across the flavedo reaching the epidermis. Affec ted cells have reduced amounts of cytoplasm located in a central position a nd have twisted and squashed walls, forming areas of collapsed cells amongs t the healthy cells of the flavedo and albedo. Comparisons of healthy and d amaged areas of affected fruits showed no significant differences in wax mo rphology and cuticular thickness or permeability. Our results suggest that an excessive loss of water from hypodermal and albedo cells is responsible for the disorder. (C) 2001 Annals of Botany Company.