Changes in apple leaf and fruit peel photosystem-II photochemistry under high light conditions

ORIOLI, GUSTAVO ADOLFO; COLAVITA, GRACIELA MARIA; BLACKHALL, VALERIA

Yangling

Simposio; I International Apple Symposium; 2016

Changes in apple leaf and fruit peel photosystem-II (PSII) photochemical process were investigated under field high light conditions (1800 µmoles.m-2.s-1) in North Patagonia. This was to increase understanding on its susceptibility to photooxidative damage. Leaves and fruits growing exposed (E), non-exposed (NE) and suddenly-exposed (SE) to high solar radiation were picked at 110 days after full bloom (DAFB). Chlorophyll content (Chl), chlorophyll a fluorescence transient (OJIP) and membrane peroxidative damage were evaluated. Total Chl decreased 26.6 and 20.6 % with high light exposition in E and SE fruits respectively, while in E leaves Chl was decreased by 24.2 % with respect to NE leaves. Chl a minimum fluorescence (Fo) decreased in E fruits. While maximum fluorescence (Fm), maximum quantum yield of PSII (Fv/Fm), and performance index on absoption basis (PIabs) decreased in E and SE fruits and leaves. Amount of active PSII reactive centres per cross section (RC/CS) increased in E fruits, while absorption flux (ABS/CS), trapped energy flux (TRo/CS), electron transport flux (ETo/CS) and reduction of end acceptors at PSI electron acceptor side per cross section (REo/CS) were reduced. Dissipated energy flux (DIo/CS) increased in SE fruits. In leaves only REo/CS and DIo/CS increased at E and SE conditions. Compared to NE, membrane peroxidative damage increased 21.4 and 11.7 % in leaves and 74.8 and 87.9 % in fruits at E and SE conditions respectively. In conclusion, a reduction in PSII photochemistry was observed in fruits at E and SE conditions. SE conditions seems to be more damaging to the fruits than leaves.