Rhizosphere Microorganisms and Plant Phosphorus Uptake

Soil microorganisms play a significant role in the transfer of phosphorus (P) within terrestrial ecosystems. Microbial processes in soil are important for the distribution of P between various inorganic and organic P fractions and subsequently for the potential availability of phosphate for plant acquisition. This chapter focuses on the contribution of soil microorganisms to plant nutrition through their capacity to increase the availability of soil P and its subsequent acquisition by plants. Emphasis is placed on the processes and mechanisms involved in P mobilization in relation to the rhizosphere. Microorganisms that interact with plant roots and their associated processes within the rhizosphere are of particular importance. Microbial influences on the availability and uptake of P by soil-grown plants are of both direct and indirect nature. Mycorrhizal fungi are effective in increasing the root-absorptive surface area, and microbial release of phytohormones may lead to enhancement of root branching and root hair development.