Abstract:The gas exchange and chlorophyll fluorescence parameters of lanceolate, oval and serrated broadoval leaves of Populus euphratica in Tarim basis were measured with chlorophyll fluorometer (PAM2100) and LI6400 Portable Photosynthesis System. The characteristics of solar radiation utilization, energy allocation and dissipation in three different leaf shapes of P.euphratica were analyzed by comparing the differences in photosynthetic parameters, in order to elucidate the ecophysiological adaptation mechanisms. The result showed that: (1) under strong solar radiation of desert region, the net photosynthetic rate (Pn), PSⅡ effective, actual photochemical quantum efficiency (Fv′/Fm′ and ΦPSⅡ) and photochemical quenching coefficient (qP) decreased, and excitation pressure (1qP), relative limitation of photosynthetic function (LPFD) increased obviously, and Fv′/Fm′, ΦPSⅡ, qP, energy of PSⅡ photochemistry transport (P) could go to near the mining level, which indicated that strong solar radiation could cause the photoinhibition of photosynthesis. However, this constituted reversible destruction to PSⅡ reaction center in three heteromorphic leaves, their PSⅡ function downregulation were an adaptation to avoid strong solar radiation damage. (2) Three typical heteromorphic leaves of P.euphratica taken different ways to adapt strong solar radiation in desert area. The oval leaves improved Fv′/Fm′, ΦPSⅡ, P to maintain higher photosynthetic capacity, in order to dissipate excess light energy and reduce the effects of excess excitation energy on photosynthetic apparatus. The serrated broadoval leaves maintained high electron transport rate (ETR) to relieve the reduced pressure of photosynthetic membrane and dissipate thermally to protect the photosynthetic apparatus avoiding light damage together, and maintain higher Pn. However, lanceolate leaves had weakness resistance for strong light, reduced Fv′/Fm′, ΦPSⅡ and allocated more absorb light energy to dissipate more excess excitation energy, further to better adapt strong solar radiation and survive. (3) Stepwise regression analysis indicated that photosynthetic capacity of serrated broadoval leaves were mainly affected by ETR and NPQ, the oval leaves and lanceolate leaves were mainly affected by Fv′/Fm′, ΦPSⅡ and NPQ, respectively. Overall, Three typical heteromorphic leaves of P.euphratica adopted different ecological strategies to adapt the desert environment with development.