Photochemical Response Characteristics of Early-Maturing Peach during Leaf Color Turned to Be Red in Summer

Taking two early-maturing peach cultivars ‘Zaomei’ and ‘Chunlei’ as materials,the changes of solar utilization and chlorophyll fluorescence characteristics of photosystem Ⅱ were studied during leaf discoloration period in summer.The results showed that,early-maturing peach had great changes in photosynthetic and chlorophyll fluorescence characteristics despite the strong differences in leaf pigment composition.Net photosynthetic rate(Pn),PSⅡ maximal photochemical efficiency(Fv/Fm) and PSⅡ actual photochemical efficiency(ФPSⅡ) of early-maturing peach increased,and there was no significantly photosynthetic inhibition during the experiment.While green leaf control ‘Honghuabitao’ showed obvious photo inhibition in July,electron transport rate(ETR),Fv/Fm and ФPSⅡ values decreased.‘Zaomei’,which was more intensely colored,was more adaptive to high temperature and strong light in summer than ‘Chunlei’ and control.Chlorophyll fluorescence quenching analysis indicate that leaf anthocyanin accumulation lead to a transitory increase of relative share of photochemical reaction(P) and heat dissipation(D) from antenna pigment absorbed light.The reddened leaves had higher photochemical quenching coefficient(qp) than green leaves,and more effective PSⅡphotochemical reactions.However,the lower non-photochemical quenching coefficient(NPQ) values shown by reddened leaves probably indicate a lower ability to dissipate safely excess photon energy than that of green leaves.