Morpho-structural description of unripe and ripe avocado pericarp (Persea americana Mill var. drymifolia)

Digital Image Analysis (DIA) was applied to pericarp tissues of unripe and ripe avocado var. drymifolia with the aim to describing morpho-structural features. When these tissues were observed under optical microscope, differences were found between both ripening stages: the unripe tissue had an exocarp with single epidermis cells in vertical disposition and a mesocarp with a dispersed monolayer of isodiametrical cells; the ripe tissue showed thickened cell walls with sclerenchymal tissue formation. Parenchymal tissue presented homogeneous shape and a bigger cell size. The Confocal Laser Scanning Microscopy also showed differences between the two ripening stages: unripe displayed two autofluorescence signals, corresponding to lignin and chlorophylls, while in ripe, a third signal was observed that corresponded to anthocyanins. The analysis of RGB channels analysis showed differences, with the ripe tissue demonstrating more intensity, reflecting pigments accumulation. Regarding the fractal analysis, Fractal dimension (F_D) resulted higher for ripe tissues due to the irregular arrangement of cells whereas, F_D and lacunarity ({n-ary logical and}) analysis per tissue section demonstrated a morphology change in the section where lipid cell accumulation occurs.