北京地区6种落叶阔叶树光合特性的研究

Photosynthetic characteristics of six broad-leaved deciduous trees in Beijing

使用Li 6 4 0 0便携式光合作用测定系统 ,对北京地区玉兰、银杏、杜仲、华东椴、马褂木和五角枫 6个落叶阔叶树种叶片的光合特性进行测定 .结果表明 :自然状态下 ,6个树种的光合曲线都呈双峰型 ,发生明显的“午休”现象 .强光、高温和低湿是引起“午休”的主要环境因子 .6个树种的气孔导度与净光合速率的变化趋势相似 ,也呈双峰型 ,但叶片胞间CO2 浓度因树种不同而呈现不同的变化趋势 .玉兰、华东椴、银杏和五角枫的胞间CO2 浓度在午间呈现谷值状态 ,而杜仲和马褂木出现了小的峰值 .因此 ,玉兰、银杏、华东椴和五角枫净光合速率降低的原因是受气孔限制 ,而杜仲和马褂木属非气孔限制 .升高CO2 浓度使 6个树种的净光合速率增大 ,光饱和点也有不同程度的增加 ,提高了叶片对光能的利用效率 ,从光合作用对CO2 浓度瞬间升高的应急反应来看 ,未来CO2 浓度加倍有利于这几个树种的光合作用 .

With the aid of Li--6400 portable photosynthesis system,the net photosynthetic rate,stomatal conductance,intercellular CO 2 concentration etc. of the leaves of six broad-leaved deciduous trees under nature and controlled conditions were measured in summer. These species were: Magnolia denudate,Ginkgo biloba,Eucommia ulmoides,Tila japonica, Liriodendron chinense and Acer mono. The results show that the diurnal variations of net photosynthetic rate of all these six species assume a typical midday depression pattern. Strong light intensity,high temperature and low air humidity are the key influencing factors. The stomatal conductance is positively related to net photosynthetic rate closely,and they keep the same change trend. But the intercellular CO 2 concentrations of these six species have different change trends: M.denudata,G.biloba,T.japonica and A. mono belong to stomata-limited photosynthesis because their intercellular CO 2 concentrations have a decreasing trend at noon. E.ulmoides and L. chinense belong to non stomata-limited photosynthesis because their intercellular CO 2 concentrations have an increasing trend. The respiration is stimulated as CO 2 concentration is elevated when photosynthesis active radiation is at 0 or 50 μmol photons/(m 2·s). Remarkable enhancement in the net photosynthetic rate with elevated CO 2 concentration is found in all the six species at higher photosynthesis active radiation and CO 2 enrichment can reduce the severity of photoinhibition.