In conclusion, the apple cultivars ‘Starkrimson’ and ‘Golden Delicious’ in a semi-arid,
cool and high-irradiant habitat of Maoxian were apt to accumulate more anthocyanin in
epidermal and sub-epidermal cells than those in a moist, warm and low-irradiant habitat of
Ya’an. Besides the key external eco-factors controlling the color formation, PAL activity,
reducing sugar content, and lenticel density, as well as cuticle thickness, and cell length and
thickness of epidermis, all were related to anthocyanin accumulation in the skin of apple.
This study provides some of the basic morphological and anatomical responses during the
coloration, which might be helpful to our understanding of anthocyanin synthesis in apple
skin.