Changes in root NH4+ and NO3- absorption rates of loblolly and ponderosa pine in response to CO2 enrichment
Changes in root NH4+ and NO3- absorption rates of loblolly and ponderosa pine in response to CO2 enrichment
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DOI：
10.1023/a:1004206624311
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发表时间：
1997-03-01
期刊：
影响因子：
4.9
通讯作者：
Strain, BR
中科院分区：
文献类型：
--
作者：
BassiriRad, H;Griffin, KL;Strain, BR
研究了火炬松和美国黄松幼苗在大气CO2浓度（35 Pa）和大气CO2 + 35 Pa（70 Pa）条件下生长160 d后根系生长和对NH 4+和NO3-的生理吸收能力。分配给活性细根的生物量比例以及单位根干质量的总N（NH 4 + + NO3-）吸收量不受CO2影响。在整个植物的基础上，CO2浓度升高导致火炬松，但不是在黄松的N收购显着增加。然而，即使在火炬松的CO2显着增加植物N的收购，相对增加，生物量远远超过了在N的增益，即60%的总干重增加伴随着只有30%的增加，在响应高CO2的N增益。我们认为，通常报道的这些和其他物种在高CO2的组织N浓度下降主要是由于根系无法充分补偿增加的N需求。CO2浓度升高显著改变了不同形态氮的根系吸收能力，即，高浓度CO2显著增加了两种植物对NO3-的吸收速率，但降低了NH 4+的吸收速率，而火炬树的降低不显著。然而，CO2浓度升高火炬松的根呼吸速率增加，而显着降低黄松。这表明，CO2诱导的变化，植物对无机氮形态的偏好是不是简单地调节根能量状态。如果植物对无机氮形态的偏好变化代表了对CO2浓度升高的典型反应，则结果可能对管理和自然植物群落中的氮动态产生重要影响。
Root growth and physiological uptake capacity for NH4+ and NO3- were examined for seedlings of loblolly and ponderosa pine grown for 160 days under two CO2 levels, ambient (35 Pa) and ambient plus 35 Pa (70 Pa). Fraction of biomass allocated to active fine roots as well as total N (NH4+ + NO3-) absorption per unit root dry mass were unaffected by CO2. On a whole-plant basis, elevated CO2 led to a significant increase in N acquisition in loblolly but not in ponderosa pine. However, even in loblolly pine where CO2 significantly increased plant N acquisition, the relative increase, in biomass far exceeded the gain in N, i.e. a 60% increase in total dry weight was accompanied by only a 30% increase in N gain in response to high CO2. We suggest that the commonly reported decline in tissue N concentration of these and other species at high CO2 is largely caused by inability of the root systems to sufficiently compensate for increased N demand. Elevated CO2 significantly altered root uptake capacity of the different N forms, i.e., high CO2 significantly increased NO3- absorption rates, but decreased NH4+ absorption rates in both species though the decrease in loblolly was insignificant. However, elevated CO2 increased root respiration rate in loblolly pine while significantly decreasing it in ponderosa pine. This indicates that CO2-induced changes in plant preference for inorganic N forms is not simply regulated by root energy status. If changes in plant preference for inorganic N forms represent typical responses to elevated CO2, the results could have important implications for N dynamics in managed and natural plant communities.