Red 'Anjou' pear has a higher photoprotective capacity than green 'Anjou'

Photoprotective function of anthocyanins along with xanthophyll cycle and antioxidant system in fruit peel was investigated in red 'Anjou' vs green 'Anjou' pear (Pyrus communis) during fruit development and in response to short-term exposure to high light. The sun-exposed peel of red 'Anjou' had higher maximum quantum yield of photosystem II (F(V)/F(M)) than that of green 'Anjou' and both the sun-exposed peel and the shaded peel of red 'Anjou' had smaller decreases in F(V)/F(M) after 2-h high light (photon flux density of 1500 mumol m(-2) s(-1)) treatment than those of green 'Anjou'. At the middle and late developmental stages, the xanthophyll cycle pool size on a chlorophyll basis, the activity of superoxide dismutase, ascorbate peroxidase (APX), monodehydroascorbate reductase (MDAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) and the level of reduced ascorbate and total ascorbate pool in the sun-exposed peel were either the same or lower in red 'Anjou' than in green 'Anjou', whereas the xanthophyll cycle pool size on a chlorophyll basis and the activity of APX, catalase, MDAR, DHAR and GR in the shaded peel were higher in red 'Anjou' than in green 'Anjou'. It is concluded that red 'Anjou' has a higher photoprotective capacity in both the sun-exposed peel and the shaded peel than green 'Anjou'. While the higher anthocyanin concentration along with the larger xanthophyll cycle pool size and the higher activity of some antioxidant enzymes may collectively contribute to the higher photoprotective capacity in the shaded peel of red 'Anjou', the higher photoprotective capacity in the sun-exposed peel of red 'Anjou' is mainly attributed to its higher anthocyanin concentration.