Effects of Different Altitudes on Photosynthetic Characters of Three Apple Cultivars in Guizhou Province

To provide the ecological basis for the extension of apple cultivation in Guizhou Province,three apple cultivars,New Gala,Fuji 2001 and Benishogun,grown in Zunyi City,Changshun County and Weining County,were used as experiment materials to investigate the effects of different altitudes on the photosynthetic characters of the apple trees.The results showed that the photosynthetic capacities of the trees tended to increase with the altitude and,with similar light intensity,New Gala in Weining showed the highest photosynthetic rate(Pn,11.22±0.70 μmol/m2·s).The response curves of Pn to PAR(photosynthetic active radiation) were logarithmic functions,with the exception of Fuji 2001 and Benishogun in Changshun(parabolic equation).The response equations of Pn to temperature(T) were parabolic,and the optimal T varied from 25.4 ℃ to 30.7 ℃,which depended on the altitudes and cultivars.Pn was in a significant positive correlation with stomatal conductance(Sc) and in a significant negative correlation with intercellular CO2 concentration(CO2 int).In Weining,a close relationship was observed between evaporation rate(Er) and Pn.No obvious correlation was noticed between Pn and relative humidity(Hr).Weining showed an obvious advantageous ecological adaptability for apple photosynthesis,and New Gala demonstrated a superior Pn irrespective of altitudes.