中文摘要：

由于环境污染、酸雨沉降及氮素化肥过度使用等原因,中国土壤已出现大规模酸化现象（Guoetal.,2010）。据报道,目前,我国土壤酸化面积已占国土面积的20%以上,随着工农业生产的不断发展,酸化面积和程度逐渐增加（易杰祥等,2006）。酸化是pH下降的结果,

英文摘要：

Malus hupehensis seedling were cultured in a 1/2 strength Hoagland solution with pH3,pH4 and pH6 to study effects of acidity in rhizosphere on their photosythesis,the net photosynthesis（Pn）,stomatal conductance（Gs）,intercellular CO2 concentration（Ci） and chlorophyll fluorescence parameters in the leaves in 8 days after tredtment.The results showed that the Pn and Gs reduced,the Ci raised;the efficiency of light energy capture by open photosystemⅡ（PSⅡ） reaction centers（F＇ v/F＇ m）,maximum photochemistry efficiency of PSⅡ（Fv/Fm）,actual quantum yield of PSⅡ（ΦPSⅡ）,photochemical quenching of PSⅡ（qP） reduced;the fluorescence intensity Fk at 300 μs increased,and the quantum yield for electron transport（φEo）,the performance index on absorption basis（PIABS） and the density of active reaction center（RC/CS） all decreased significantly.Furthermore,the range of variation of these parameters increased with reducing pH the solution of rhizosphere.These results displayed that rhizosphere acidification damaged the oxidation and reduction sides of the reaction centers of PSⅡ of the leaves in M.hupehensis,and further decreased the activity of PSⅡand Pn.