The leaf photosynthetic characteristics in autumn of evergreen arbor Euonymus japonicus Thunb were studied with the Li-6400 portable photosynthesis system.The results showed that there was a positive relationship between the net photosynthetic rate (Pn)and transpiration rate(Tr)and stomatal con-ductance(Gs ),there was a negative relationship between the net photosynthetic rate and internal CO2 (Ci ) concentration.The net photosynthetic rate presented a double-peak curve which showed obvious midday depression.The maximum of net photosynthetic rate was 3.54 μmol/(m2 · s),and the light saturation point (LSP)was 1 225.00μmol/(m2 ·s),the light compensation point (LCP)was 21.85μmol/(m2 ·s) when the density of CO2 was up to 400.00μmol/mol.Therefore,it indicated that E.japonicus was a typical masculine shade-resistant plant which was strongly able to adapt circumstance.%以多年生大叶黄杨为研究对象,采用 Li-6400便携式光合测定仪测定其光合生理指标的日变化和光合指标响应.结果表明：叶片净光合速率(Pn )与气孔导度(Gs )、蒸腾速率(Tr )呈现正相关,与胞间 CO2浓度(Ci )呈负相关；Pn 日变化呈双峰型,存在着光合“午休”现象；叶片日最大Pn 为3.54μmol/(m2·s),Ci 为400.00μmol/mol时,叶片光饱和点为1225.00μmol/(m2·s),光补偿点为21.85μmol/(m2·s).大叶黄杨对光照的适应性较强,为典型的阳性耐阴植物.
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