How plants balance different strategies to acquire resources from the environment is a basic question in biology and ecology. Phosphorus (P) uptake by mycorrhizal plants comprises direct pathway (DP) and mycorrhizal pathway (MP). It is unknown whether there is a trade-off between DP and MP and how plants govern selection and/or differential contributions of the two pathways. We used ³²P labelling technique to quantify P uptake by both pathways in three maize genotypes differing in P acquisition at Olsen P values of 4.5, 8 and 50 mg kg⁻¹, representing low, suboptimal and high P supplies, respectively. We calculated the preference index of P uptake (ratio of MP contribution to DP contribution), P-transporter-based preferential index, C investment index as (ratio of hyphal length to root length), and the P-efficiency-based preferential index. Our results showed that maize plants preferred MP at the suboptimal soil available P because both the C investment index and the P-efficiency-based preferential index were greatest at that P supply. Shoot P content showed a significant relationship with the P uptake preference index, suggesting shoot P demand governed the trade-off between DP and MP. In conclusion, the preference for DP or MP regarding P acquisition in maize shifts with changes in soil available P level. These findings could be harnessed to better manage mycorrhizal fungi to enhance the sustainability of agricultural crops in soils with suboptimal P availability.

植物如何平衡不同的策略以从环境中获取资源是生物学和生态学中的一个基本问题。菌根植物对磷（P）的吸收包括直接途径（DP）和菌根途径（MP）。目前尚不清楚 DP 和 MP 之间是否存在权衡以及植物如何控制这两种途径的选择和/或差异贡献。我们使用³² P 标记技术来量化三种玉米基因型中两种途径对 P 的吸收，这些基因型在 Olsen P 值为 4.5、8 和 50 mg kg ^{-1 时}P 获取不同，分别代表低、次优和高磷供应。我们计算了 P 吸收的偏好指数（MP 贡献与 DP 贡献的比率）、基于 P 转运蛋白的优先指数、C 投资指数为（菌丝长度与根长度的比率）和基于 P 效率的优先指数。我们的结果表明，玉米植物在次优土壤有效磷下偏爱 MP，因为 C 投资指数和基于 P 效率的优先指数在该 P 供应下都最大。茎秆 P 含量与 P 吸收偏好指数显着相关，表明茎秆 P 需求控制了 DP 和 MP 之间的权衡。总之，玉米中磷获取对 DP 或 MP 的偏好随着土壤有效磷水平的变化而变化。