Competition between Zea mays genotypes with different root morphological and physiological traits is dependent on phosphorus forms and supply patterns

Abstract

Each genotype within species has a particular combination of root morphological and/or physiological traits to adapt to phosphorus-limited environments, which can lead to its unique plant fitness and competitive ability. Yet, how the various phosphorus environments affect the competition between genotypes remains obscure. Two maize (Zea mays L.) genotypes (XY335 and HMY, bred in nutrient-rich and nutrient-poor environments, respectively) were grown in monoculture and mixture in phosphorus-limited soil with homogeneous or heterogeneous supply patterns and inorganic (Pinorg) or organic phosphorus (Porg) forms. In homogeneous Pinorg and Porg environments, XY335 had higher root length and surface area, but lower mycorrhizal colonization and the acid phosphatase and phytase activities in the rhizosphere, than HMY. In heterogeneous phosphorus environments, XY335 had higher root proliferation than HMY. The root trait divergence influenced the competition in mixture: XY335 had a competitive advantage compared to HMY under heterogeneous phosphorus conditions, whereas HMY exhibited a stronger competitive ability in homogeneous phosphorus treatments; these reverse trends were more significant in the Porg than Pinorg treatments. The results suggested the importance of root physiological traits in homogeneous phosphorus-limited soil environments, whereas P acquisition strategy based on root morphological traits favours heterogeneous phosphorus supply.