Agriculture Reference
In-Depth Information
Chapter 2
Mechanism of Phosphate Solubilization
and Physiological Functions of
Phosphate-Solubilizing Microorganisms
Md. Saghir Khan, Almas Zaidi, and Ees Ahmad
Abstract
Phosphorus (P) is the second important key plant nutrient after nitrogen.
An adequate supply of P is therefore required for proper functioning and various
metabolisms of plants. Majority of P in soils is fixed, and hence, plant available P is
scarcely available despite the abundance of both inorganic and organic P forms in
soils. A group of soil microorganisms capable of transforming insoluble P into
soluble and plant accessible forms across different genera, collectively called
phosphate-solubilizing microorganisms (PSM), have been found as best eco-
friendly option for providing inexpensive P to plants. These organisms in addition
to supplying soluble P to plants also facilitate the growth of plants by several other
mechanisms, for instance, improving the uptake of nutrients and stimulating the
production of some phytohormones. Even though several bacterial, fungal and
actinomycetal strains have been identified as PSM, the mechanism by which they
make P available to plants is poorly understood. This chapter focuses on the
mechanism of P-solubilization and physiological functions of phosphate
solubilizers in order to better understand the ecophysiology of PSM and conse-
quently to gather knowledge for managing a sustainable environmental system.
Conclusively, PSM are likely to serve as an efficient bio-fertilizer especially in
areas deficient in P to increase the overall performance of crops.
Keywords
Phosphate solubilization • Mineralization • Organic acids • Plant
growth regulators • ACC deaminase
