Differential Phosphorus Acquisition Strategies and Adaptive Mechanisms Evolved by Three Lespedeza Species to Tackle Phosphorus Deficiency.

Phosphorus (P) is essential for plant growth but is frequently limited in soils. Lespedeza species are well-known for their ecological and economic benefits, as well as their tolerance to nutrient-poor soils. This study investigated the P acquisition strategies and adaptive mechanisms of three Lespedeza species (L. davurica, L. bicolor, and L. cuneata), focusing on biomass allocation, P distribution, root exudation, and absorption kinetics under P deficiency. Under P deficiency, L. davurica and L. bicolor allocated more biomass to roots to enhance P acquisition, whereas L. cuneata increased specific root length and area. Moreover, all three species preferentially allocated P to roots, but L. bicolor showed higher P content in stems and leaves than the others. P absorption kinetics indicated that Michaelis constant (Km) and equilibrium concentration (Cmin) were significantly decreased in all three species under P deficiency, with L. bicolor exhibiting the strongest P affinity and acquisition capacity. Secretion analysis revealed that while L. davurica and L. cuneata secreted higher levels of organic acids under P deficiency, exudates from L. bicolor were significantly enriched in acid phosphatase activity. Overall, the three Lespedeza species developed distinct P acquisition and adaptive strategies to cope with P deficiency, with L. bicolor demonstrating the greatest low-P tolerance and most efficient adaptive mechanisms.