Abstract: With 'Hanfu' apple and its parents 'Dongguang' and 'Fuji' apples as the materials, the effects of weather conditions, seasonal factors and leaf position on the photosynthetic characteristics were studied by using CIRAS-1 Portable Photosynthesis System. The results showed that diurnal change of net photosynthetic rate (P_n) of leaves in 'Hanfu' apple and its parents was a typical bimodal curver in a sunny day, with two peaks (13.47μmol·m^-2·s^-1，12.46 μmol·m^-2·s^-1，11.21 μmol·m^-2·s^-1and 11.92 μmol·m^-2·s^-1, 10.94μmol·m^-2·s^-1, 9.84 μmol·m^-2·s^-1respectively) appeared at 10:00 and 14:00, respectively. And obvious "noon rest" phenomenon of Pn happened in daytime. As far as that was in a cloudy day, the curve changed into unimodal, with the peak (11.0 μmol·m^-2·s^-1, 10.2 μmol·m^-2·s^-1 and 10.3 μmol·m^-2·s^-1) appeared at around 12:00, and the diurnal mean Pn was 2.28 μmol·m^-2·s^-1, 2.86 μmol·m^-2·s^-1 and 2.86 μmol·m^-2·s^-1 below a sunny day. The seasonal variation of P_n of leaves in 'Hanfu' apple and its parents was found as an unsymmetrical double-peak curve, with two peaks appeared in the early July and September, respectively. The variation of P_nin leaves at differrent nodes on new shoots was a parabola type curve, and those at the upper and middle nodes were higher than that of lower nodes. The light compensation point (LCP) of leaves in 'Hanfu' apple and its parents were 5.9±1.8 μmolm^-2·s^-1, 21.1±1.4 μmol·m^-2·s^-1and 9.05±2.1 μmol·m^-2·s^-1, and the saturation point (LSP) were 1665±20 μmol·m^-2·s^-1, 1418±131 μmol·m^-2·s^-1 and 1300±56.6 μmol·m^-2·s^-1, respectively. The the CO2 compensation point(CCP) were 87.5±1.4 μmol·mol^-1, 84.2±5.9 μmol·mol^-1and 59.5±7.5 μmol·mol^-1 , and the saturation point(SC) were 2961±41 μmol·mol^-1, 1572±166 μmol·mol^-1 and 1381±23 μmol·mol^-1 respectively. The photosynthetic capacity of 'Hanfu' apple was stronger than that of its parents in both high and low light conditions to indicate that 'Hanfu' apple was a photophil and shade-tolerant plants.

Key words: apple, cool climate regions, cultivar, photosynthetic characteristics