Thehigh UV-Bdosage employedinour study causedno apparent
damage to the photosystem of previously sun-exposed apple fruit
peel. Some cultivars appear to have increased their xanthophyll
cycles, while others may have increased their photosynthetic rates.
‘Cripps’ Pink’ fruits seemed to depend more on the xanthophyll
cycle for photoprotection after UV-B stress at maturity compared
to the other cultivars tested.Incontrastto sun-adaptedpeel, shaded
peel of ‘Granny Smith’ and ‘Fuji’ were sensitive to UV-B treatment.
Apple fruit that are exposed to sunlight from early development
seem to be well protected against UV-B and are unlikely to develop
sunburn in response to UV-B exposure. Shaded fruit in contrast
are not as well protected and may be damaged by sudden UV-B
exposure.