RIND STRUCTURE, EPICUTICULAR WAX MORPHOLOGY AND WATER PERMEABILITY OFFORTUNE MANDARINE FRUITS AFFECTED BY PEEL FITTING

Rind structure and surface wax morphology of 'Fortune' mandarins affec ted by pre-harvest peel pitting were examined as related to the severi ty of this disorder. In fruits with slight symptoms of pitting (< 10% surface area pitted) a discrete number of epidermal cells were injured with signs of cellular breakdown. in fruits with moderate symptoms of pitting (10-50% surface area pitied) the injured zones also involved hypodermal cells. The surface of rind had an undulating appearance in fruits with severe symptoms of pitting (> 50% surface area pitted). Th e depressed areas in these fruits were devoid of crystalline wax struc tures and had a rough morphology. Broad regions of rind had crushed ep idermal and hypodermal cells with infolded walls. These cells were eit her empty or filled with reduced cytoplasm amounts located in central positions of the cell. No signs of disruption in the cuticle were obse rved. Under field conditions, pitting occurrence coincided with higher permeability values of isolated cuticles. Furthermore, length of cold treatments required to show post-harvest pitting symptoms was shorter in fruits sampled at this stage than in those collected earlier or la ter. Our results indicate that the low temperatures induce the breakdo wn of the more external cellular strata of the rind. Thus, the physiol ogical function of cuticle is highly impaired which, in turn, increase s water permeability considerably.