Plant carbon (C) partitioning—the relative use of photosynthates for biomass production, respiration, and other plant functions—is a key but poorly understood ecosystem process. In an experiment with Zea mays, with or without arbuscular mycorrhizal fungi (AMF), we investigated the effect of phosphorus (P) fertilization and AMF on plant C partitioning. Based on earlier studies, we expected C partitioning to biomass production (i.e., biomass production efficiency; BPE) to increase with increasing P addition due to reduced C partitioning to AMF. However, although plant growth was clearly stimulated by P addition, BPE did not increase. Instead, C partitioning to autotrophic respiration increased. These results contrasted with our expectations and with a previous experiment in the same set‐up where P addition increased BPE while no effect on autotropic respiration was found. The comparison of both experiments suggests a key role for AMF in explaining these contrasts. Whereas in the previous experiment substantial C partitioning to AMF reduced BPE under low P, in the current experiment, C partitioning to AMF was too low to directly influence BPE. Our results illustrate the complex influence of nutrient availability and mycorrhizal symbiosis on plant C partitioning.

中文翻译：

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在玉米的实验中，添加磷增加了对自养呼吸的碳分配，但并未增加对生物量的生产。

植物碳（C）的分配（光合产物在生物质生产，呼吸和其他植物功能中的相对使用）是一个关键但鲜为人知的生态系统过程。在Zea mays的实验中不论是否存在丛枝菌根真菌（AMF），我们研究了磷（P）施肥和AMF对植物C分配的影响。根据较早的研究，我们预计由于分配给AMF的碳减少，随着磷添加量的增加，分配给生物质的碳分配量（即，生物质生产效率； BPE）也会增加。但是，尽管添加P明显刺激了植物的生长，但BPE却没有增加。相反，C分配为自养呼吸增加了。这些结果与我们的预期以及先前在相同设置中进行的实验形成对比，在该实验中，添加P增加了BPE，而未发现对自发性呼吸的影响。两项实验的比较表明，AMF在解释这些差异方面起着关键作用。在先前的实验中，在低P下大量C分配给AMF会降低BPE，而在当前实验中，C分配给AMF太低而无法直接影响BPE。我们的结果说明了养分利用率和菌根共生对植物C分配的复杂影响。