大气CO2体积分数升高对植物N素吸收的影响

从影响植物N素吸收的因素来看，大气CO2体积分数升高条件下植物净光合作用增强，碳同化产物增多，利于改善N素吸收的能量和物质基础：植物根系生长增强，生物量增多且空间分布加大，有利于N素吸收；但土壤有效N供应能力的变化存在增强和减弱两种观点。从植物N素吸收的实际情况来看，大气CO2体积分数升高条件下植物N吸收总量并末增加，植物体内N质量分数普遍降低，某些种类植物N吸收形态也发生了改变。因此要阐明大气CO2体积分数升高对植物N素吸收的影响机制，必须探明土壤有效N供应能力的变化：CO2体积分数升高条件下N矿化作用是否增强，微生物和植物间是否存在对有效N的竞争，此外，CO2体积分数升高条件下植物根系形态特征变化和N素吸收(包括主动和被动吸收)的生理机制及其与环境因素的关系也值得进一步研究。

Effect of elevated atmospheric CO2 on nitrogen uptake by plant

In this paper, the effect of elevated atmospheric CO2 on plant nitrogen uptake was briefly reviewed. Carbohydrate accu-mulation in plant tissues as the result of stimulated photosynthesis under elevated CO2 might favor plant N uptake; elevated atmos-pheric CO2 also increased biomass and volume of the root system, thus allowing a greater exploitation of available N; but the effect of elevated atmospheric CO2 on soil N availability is still in dispute by now. However, plants did not always uptake more nitrogen and tissue N concentrations were decreased due to elevated atmospheric CO2. And elevated atmospheric CO2 also had influence on the form of N uptaken by some plant species. Thus, the effect of elevated CO2 on soil N availability, or in other words, changed N mineralization and the possible compitition for available N between soil microbial and plants could have major implications in plant N uptake. Besides, further research on physiological mechanism of altered root morphological characteristics and root N uptake are necessary.