Photoabatement by anthocyanin shields photosynthetic systems from light stress

摘要

Reddish-purple pods from Bauhinia variegata cv. Purpurea and green pods from cv. Candida were exposed to red (RR) or blue-green radiation (BGR). Photon yields of photosystem II (PSII) photochemistry and photochemical chlorophyll fluorescence quenching coefficients (qP), measured over a range of photon flux densities (PFD) up to 1200μmol m-2 s-1 at 23deg C and at 5 temperatures between 8 and 28deg C at a PFD of 260μmol m-2 s-1, were almost identical in green pods irradiated with either RR or BGR and inpurple pods irradiated with RR. However, qP values were much higher in purple pods irradiated with BGR, indicating that photoabatement by anthocyanin allowed the first stable acceptor of PSII, QA, to be kept in a more oxidized state, thus decreasing thelikelihood of photoinhibition. This was confirmed by demonstrating a lower susceptibility to photoinhibition in purple pods than in green pods in sunlight, either naturally in pods on trees or in detached pods exposed to photoinhibitory conditions.