engleski

Photosynthetic response of young and mature fig leaves to high irradiation

High irradiation often causes photoinhibition due to limited electron transport and reduced photosynthetic quantum conversion. We aimed to investigate influence of high irradiation on photosynthetic performance of young (YL) and mature (ML) fig leaves (Ficus carica L.) exposed to elevated temperature. Detached YL and ML were acclimated at room temperature in darkness for 12h and then exposed to 35±1°C combined with low (LI, ~50 µmolm-2s-1) or high irradiation (HI, ~800 µmolm-2s-1) for 4h. To evaluate primary photochemistry of photosystem II (PSII), modulated chlorophyll a fluorescence was measured. High maximum quantum yield of PSII photochemistry (Fv/Fm) indicated full functionality of both leaf types exposed to LI. Exposure of ML to HI induced significant reduction of Fv/Fm, followed with decreased electron transport rate (ETR) and non- photochemical quenching (NPQ). Increase in the quantum yield of non-regulated energy dissipation (Y(NO)), accompanied with decline in both, the effective quantum yield of photochemical energy conversion in PSII (Y(PSII)) and the quantum yield of pH-dependant energy dissipation (Y(NPQ)), suggested reduced capacity of photoprotective reactions. YL exposed to HI showed no significant difference in all measured parameters compared to LI, thus indicating stable photosynthetic performance. In conclusion, YL maintained efficient photoprotective mechanisms at HI, while increased susceptibility of ML to HI resulted with severe photoinhibition.

 Ficus carica L.;  photosynthesis;  light stress;  chlorophyll a fluorescence

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