Kinetics of nitrogen uptake by Populus tremuloides in relation to atmospheric CO(2) and soil nitrogen availability.
Kinetics of nitrogen uptake by Populus tremuloides in relation to atmospheric CO(2) and soil nitrogen availability.
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DOI：
10.1093/treephys/20.4.265
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发表时间：
2000-03
期刊：
影响因子：
4
通讯作者：
D. Rothstein;D. Zak;K. Pregitzer;P. Curtis
中科院分区：
文献类型：
--
作者：
D. Rothstein;D. Zak;K. Pregitzer;P. Curtis
植物产量的持续增加对大气中二氧化碳（CO（2））浓度升高的响应可能受到土壤氮（N）有效性的限制。然而，这是可能的，植物将响应N限制在CO（2）浓度升高，通过增加比N吸收能力的根。为了探索这种可能性，我们研究了（15）NH（4）（+）和（15）NO（3）（-）的离体根的吸收动力学山杨。生长在环境和两倍环境的CO（2）浓度，并在土壤中的低和高氮的可用性。高浓度的CO2对NH 4+和NO3-的吸收没有影响，而高浓度的N降低了根系吸收NH 4+和NO3-的能力。从土壤氮有效性低到高，NH（4）（+）吸收的最大速率从12下降到8 mol g（-1）h（-1），K（m）从49增加到162 mol l（-1）。由于NO（3）（-）吸收在我们使用的浓度范围内表现出混合动力学（10-500 mol l（-1）），因此无法计算V（max）和K（m）。相反，我们使用100 mol g（-1）h（-1）的吸收速率作为我们对NO（3）（-）吸收能力的度量，在低氮和高氮可用性下，其平均值分别为0.45和0.23 mol g（-1）h（-1）。在高氮可用性降低氮吸收能力的近端机制似乎是在细根碳水化合物状态的增加和细根氮浓度的降低。NH（4）（+）和NO（3）（-）吸收量与细根N浓度呈负相关，与细根总非结构性碳水化合物浓度呈正相关。我们得出的结论是，土壤氮的有效性，通过其对细根N和碳水化合物的状态的影响，有更大的影响比大气CO（2）升高的细根的比吸收能力。在大气CO2浓度升高的情况下，山茱萸氮吸收的变化似乎是由根结构和生物量的变化驱动的，而不是由氮吸收酶的数量或活性的变化驱动的。
Sustained increases in plant production in response to elevated atmospheric carbon dioxide (CO(2)) concentration may be constrained by the availability of soil nitrogen (N). However, it is possible that plants will respond to N limitation at elevated CO(2) concentration by increasing the specific N uptake capacity of their roots. To explore this possibility, we examined the kinetics of (15)NH(4) (+) and (15)NO(3) (-) uptake by excised roots of Populus tremuloides Michx. grown in ambient and twice-ambient CO(2) concentrations, and in soils of low- and high-N availability. Elevated CO(2) concentration had no effect on either NH(4) (+) or NO(3) (-) uptake, whereas high-N availability decreased the capacity of roots to take up both NH(4) (+) and NO(3) (-). The maximal rate of NH(4) (+) uptake decreased from 12 to 8 mol g(-1) h(-1), and K(m) increased from 49 to 162 mol l(-1), from low to high soil N availability.Because NO(3) (-) uptake exhibited mixedkinetics over the concentration range we used (10-500 mol l( -1)), it was not possible to calculate V(max) and K(m). Instead, we used an uptake rate of 100 mol g(-1) h(-1) as our metric of NO(3) (-) uptake capacity, which averaged 0.45 and 0.23 mol g(-1) h(-1) at low- and high-N availability, respectively. The proximal mechanisms for decreased N uptake capacity at high-N availability appeared to be an increase in fine-root carbohydrate status and a decrease in fine-root N concentration. Both NH(4) (+) and NO(3) (-) uptake were inversely related to fine-root N concentration, and positively related to fine-root total nonstructural carbohydrate concentration. We conclude that soil N availability, through its effects on fine-root N and carbohydrate status, has a much greater influence on the specific uptake capacity of P. tremuloides fine roots than elevated atmospheric CO(2). In elevated atmospheric CO(2), changes in N acquisition by P. tremuloides appeared to be driven by changes in root architecture and biomass, rather than by changes in the amount or activity of N-uptake enzymes.