Difference in photosynthetic performance among three peach cultivars grown under low light conditions in greenhouses
The effects of low photosynthetic photon flux density (PPFD) on greenhouse grown peach trees (‘Qingfeng’: Prunus persica L. Batsch, ‘NJN76’: Prunus persica L. Batsch and ‘Maixiang’: P. persica var. nectarine) were investigated. Difference in photosynthesis rate (Pn) and stoma morphology among cultivars were studied. Furthermore, chlorophyll content, leaf thickness and photosynthesis enzyme activity were analyzed. Results showed that when PPFD was reduced to 80% of control, Pn decreased in all three cultivars. The reduced net photosynthesis rate was associated with decreased stoma density, stoma aperture and stoma conductance (Cs), as well as chlorophyll a (Chla) and b (Chlb) content in all cultivars; leaf mass per unit area (LMA) and thickness of upper and lower layers of leaf epidermis also declined. At 80% PPFD, the variation pattern of ribulose bisphosphate carboxylase (RuBPCase), Ca2+- adenosinetriphosphatase (Ca2+-ATPase) and Mg2+- adenosine triphosphatase (Mg2+-ATPase) activities, together with nicotinamide adenine dinucleotide phosphate (NADPH) content and photosynthetic O2 evolution rate among the three cultivars was the same as the pattern of LMA. Time course analysis showed that the net photosynthesis rate of ‘Maixiang’ was higher than that of the other two cultivars from 10:00 to 14:00. Though the parameters mentioned above decreased under shade in all the three cultivars, ‘Maixiang’ still had higher Pn than that of the other two cultivars. Our results indicated that ‘Maixiang’ is probably more suitable to grow in low PPFD than ‘Qingfeng’ and ‘NJN76’, especially in the early spring season in order to get higher market value.
Key words: Prunus persica L., low light, photosynthesis, RuBPcase, Ca2+-ATPase, Mg2+-ATPase, NADPH content.