Perkowski Evan A, Terrones Joseph, German Hannah L, Smith Nicholas G
Department of Biological Sciences, Texas Tech University, Lubbock, USA.
AoB Plants. 2024 Sep 12;16(5):plae051. doi: 10.1093/aobpla/plae051. eCollection 2024 Oct.
Many plant species form symbiotic associations with nitrogen-fixing bacteria. Through this symbiosis, plants allocate photosynthate belowground to the bacteria in exchange for nitrogen fixed from the atmosphere. This symbiosis forms an important link between carbon and nitrogen cycles in many ecosystems. However, the economics of this relationship under soil nitrogen availability gradients is not well understood, as plant investment toward symbiotic nitrogen fixation tends to decrease with increasing soil nitrogen availability. Here, we used a manipulation experiment to examine how costs of nitrogen acquisition vary under a factorial combination of soil nitrogen availability and inoculation with in L. (Merr.). We found that inoculation decreased belowground biomass carbon costs to acquire nitrogen and increased total leaf area and total biomass, but these patterns were only observed under low fertilization and were the result of increased plant nitrogen uptake and no change in belowground carbon allocation. These results suggest that symbioses with nitrogen-fixing bacteria reduce carbon costs of nitrogen acquisition by increasing plant nitrogen uptake, but only when soil nitrogen is low, allowing individuals to increase nitrogen allocation to structures that support aboveground growth. This pattern may help explain the prevalence of plants capable of forming these associations in less fertile soils and provides useful insight into understanding the role of nutrient acquisition strategy on plant nitrogen uptake across nitrogen availability gradients.
许多植物物种与固氮细菌形成共生关系。通过这种共生关系，植物将光合产物分配到地下供给细菌，以换取从大气中固定的氮。这种共生关系在许多生态系统的碳循环和氮循环之间形成了重要的联系。然而，在土壤氮有效性梯度下这种关系的经济学原理尚未得到充分理解，因为植物对共生固氮的投入往往会随着土壤氮有效性的增加而减少。在这里，我们通过一项操控实验来研究在土壤氮有效性与接种 （Merr.）的因子组合下，氮获取成本是如何变化的。我们发现，接种降低了获取氮的地下生物量碳成本，并增加了总叶面积和总生物量，但这些模式仅在低施肥条件下观察到，并且是植物氮吸收增加以及地下碳分配不变的结果。这些结果表明，与固氮细菌的共生关系通过增加植物氮吸收来降低氮获取的碳成本，但仅在土壤氮含量较低时如此，这使得个体能够将更多氮分配到支持地上生长的结构中。这种模式可能有助于解释在肥力较低的土壤中能够形成这些共生关系的植物的普遍存在，并为理解养分获取策略对植物在不同氮有效性梯度下氮吸收的作用提供了有用的见解。
