中文摘要：

以北方阔叶树种山梨（Pyrus ussuriensis）和山荆子（Malus baccata）1年生苗木为材料,采用土壤和风化砂混合物作为盆栽基质,设置0（CK）、100、500、1 000、2 000mg.kg-15种土壤铅浓度,研究了土壤铅胁迫对苗木叶片光合作用和叶绿素荧光特性的影响。结果表明：随着土壤铅胁迫浓度增加,山梨的净光合速率（Pn）持续下降,气孔导度（Gs）先升后降、胞间二氧化碳浓度（Ci）和蒸腾速率（Tr）持续升高;同时山荆子的Pn和Gs先升后降,Ci在100mg.kg-1出现谷值,随后逐渐升高,Tr持续升高;随土壤铅处理浓度的增加,山梨的Fv/Fm、Fv/Fo和qN逐渐增加,山荆子逐渐下降,qP和ФPSⅡ二者均表现为先升后降。研究发现,铅污染胁迫导致的Pn的下降是由非气孔限制因素所致;铅污染对山梨叶绿素荧光特性起促进作用,对山荆子影响不显著（p〈0.05）;综合各项参数山梨对土壤铅的耐性〉山荆子。

英文摘要：

One-year-old seedlings of two broadleaved trees occurring in Northern China, Pyrus ussuriensis and Malus baccata were potted in the mixed substrates of soil and weathered sand, in which different con- centrations of lead salt （0, 100, 500, 1 000, and 2 000 mg·kg-1） were applied to examine the influence of Pb on the photosynthesis and chlorophyll fluorescence characteristics in the leaves of the seedlings tested. The results showed that with the increase of Pb concentration, Pn of P. ussuriensis declines continuously; G, first increased and then decreased; Ci and Tr increased continuously; Fv/Fm, Fv/Fo and qN gradually increased. For M. baccata, Pn and G, first increased and then decreased; Ci appeared minimum value in the Pb concentration of 100 mg·kg-1 and then gradually increased; Tr increased continuously; Fv/Fm, Fv/ Fo and qN gradually declined. Values of qP and ФPSⅡ in the leaves of two species showed first increased and then decreased. The decline of Pn in the leaves under lead stress was resulted from non-stomatal limi- tation factors. The stress promoted chlorophyll fluorescence characteristics for P. ussuriensis, while had no significant effect （p〈0.05） on M. baccata. Comprehensive parameters of Pb on soil show that lead tolerance of P. ussuriensis was stronger than M. baccata.