中文摘要：

在盆栽半控制试验中，采用两因素的随机区组设计，在3个土壤水分梯度（分别为80％、50％和30％的田间持水量（FC）下研究了施氮肥和不施氮肥处理麻疯树（Jatropha curcas）幼苗的光合特性。比较了不同水分和氮素供应条件下麻疯树幼苗的光合一光响应和CO2响应曲线、PSII的最大光化学效率（Fv／Fm）、氮含量和光合色素含量之间的差异。结果表明：1）施氮肥处理中，随着土壤水分含量的增加，叶片表观量子效率（AQY）、光补偿点、最大净光合速率、羧化效率、光呼吸速率、暗呼吸速率和叶片氮含量均呈现增加的趋势，而且均在80％FC下最高。2）不施氮肥处理中，随着土壤水分含量的增加，麻疯树各光合参数均与施氮肥处理呈现相反的变化趋势。3）在30％FC下，施氮肥处理和不施氮肥处理相比，氮含量显著增加，4Qy、F／Fm、光合色素含量无显著的变化，其他各项指标均显著降低。这些结果表明，水氮耦合效应对麻疯树光合特性有显著影响，尤其是在80％FC下增施氮肥的效果最为明显。因此，在土壤氮素含量不高的情况下，麻疯树更适宜在较低的土壤水分下生长，土壤水分较高反而不利于麻疯树的光合作用；而如果增施氮肥，麻疯树在土壤水分含量较高时生长更好。

英文摘要：

Aims Jatropha curcas is a drought-resistant perennial that can be used for bio-energy to replace petro-diesel. However, J. curcas is still a wild plant and basic agronomical properties are not thoroughly understood. When it is grown in commercial plantations with regular irrigation, we do not know how J. curcas will respond to changes in the environment. Our objective was to evaluate the effects of different soil water and nitrogen supplies on the photosynthesis characteristics ofJ. curcas seedlings. Methods We exposed seedlings ofJ. curcas to three watering regimes （80%, 50% and 30% of field water holding capacity （FC）） and two nitrogen （N） regimes （with or without N-fertilization） and determined how N-fertilization affects the photosynthetic light and CO2 response curve, maximal quantum yield of PSII, and N and pigments contents under different soil water conditions. Important findings With N-fertilization, we detected significant increases in apparent quantum yield （AQY）, light compensation point （LCP）, maximum net photosynthetic rate （Pmax）, carboxylation efficiency （CE）, photo- respiration rate （Rp）, dark respiration rate （Rd） and nitrogen content with the increase of soil water content. Highest values of photosynthesis parameters occurred with 80% FC with N-fertilization. Without N-fertilization, all pho- tosynthesis parameters had the opposite trends with the increase of soil water content. Furthermore, with 30% FC the nitrogen content of seedlings with N-fertilization was significantly higher than without N-fertilization. AQY, PSII maximum photochemical efficiency （Fv/Fm） and chlorophyll and carotenoids contents was nearly the same with and without N-fertilization, but other parameters were significantly lower without N-fertilization. Thus, un- der N-poor soil condition J. curcas grew better under the relatively low soil water conditions and photosynthesis ofJ. curcas was impacted by high soil water content. While with N-fertilization, J. curcas performed better