Can anthocyanin presence ameliorate the photosynthetic performance of Prunus saplings subjected to polyethylene glycol-simulated water stress?

The aim was the evaluation of the biochemical and physiological responses of green- (GP) and red-leafed (RP) Prunus cerasifera mature leaves to 20 d of polyethylene glycol (PEG 6000)-induced water stress in order to elucidate a possible ameliorative role exerted by anthocyanins. At 10 d, the anthocyanin content remained unchanged in RP water-stressed leaves. Photosynthetic rate was lower in GP than that of RP (83.4 vs. 76.5%, respectively), paralleled by a higher degree of photoinhibition (Fv/Fm) in GP leaves. Leaves of GP accounted for higher content of soluble sugars at 10 d, when RP only showed a slight sucrose increase. At 20 d of stress, both morphs recovered their Fv/Fm values, suggesting the ability of both genotypes to adjust their photosynthetic metabolism under conditions of water stress. In conclusion, besides the sunscreen role served by anthocyanins, the carbon sink by these flavonoids might have further prevented sugar accumulation and the consequent sugar-promoted feedback regulation of photosynthesis in drought-stressed red leaves.