Review: Adaptive strategies for N metabolism in P deficient legume nodules ($)

Legume nodules fix N, but their function has a high requirement for P, making nitrogen-fixation highly sensitive to P deficiency. Valentine et al. review how P limitation affects nodule function and also how nodules respond and adapt to P deficiency, drawing largely on studies of Virgilia divaricata, a legume endemic to P-poor soils of South Africa. One way that P deficiency affects nodule function is through the ADP:ATP ratio; N fixation and export from nodules has a high demand for energy.  Although nodules are strong sinks for P, with P limitation NO₃^– and NH₄⁺ can become preferred N sources (over N₂), a switch that impacts amino acid and carbon skeleton availability. Lessons from this tropical legume can point to potential traits for legume crop improvement in other nutrient-poor ecosystems. Plant Science 10.1016/j.plantsci.2016.12.010