Mechanism of Phosphate Solubilization and Physiological Functions of Phosphate-Solubilizing Microorganisms

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 ecofriendly 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 consequently 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.

Phosphate solubilization by fungi with nematicidal potential

“…This finding may indicate that the production of organic acids is not the only mechanism for iron phosphate solubilization. Some microorganisms are able to solubilize P from inorganic compounds by simply lowering the pH, which occurs as a result of fungal metabolism and promotes the solubility of some highly soluble phosphate compounds (Barroso and Nahas, 2005;Sharma et al, 2013;Li et al, 2016 (Dorozhkin, 2011;Khan et al, 2014). Because these compounds are hard insoluble P sources, in vitro testing with a culture that includes these compounds is one of the first steps in the selection of microorganisms with a solubilizing capacity (Bashan et al, 2013).…”

Mineralization of soluble P fertilizers and insoluble rock phosphate in response to phosphate-solubilizing bacteria and poultry manure and their effect on the growth and P utilization efficiency of chilli (<i>Capsicum annuum</i> L.)

“…Hence, the recovery efficiency of P is not more than 20 % of applied P in the world soils (Qureshi et al, 2012). Considering the low recovery of applied and native P and the high cost of chemical phosphatic fertilizers in addition to an increasing concern about environmental degradation (Aziz et al, 2006;Khan et al, 2014), it is important to find viable solutions to increase P fertilizer use efficiency. Two management options can be effective: (i) increasing the recovery and solubility of applied P fertilizers and (ii) replacing the expensive chemical P fertilizers with novel, cheaper, more ecologically friendly but nevertheless efficient P sources, such as indigenous rock phosphates (RPs).…”

“…Soil microorganisms have generally been found effective in making P available to the plants from both inorganic and organic sources by solubilizing and mineralizing complex P compounds (Wani et al, 2007;Khan et al, 2014). In particular, P-solubilizing bacteria (PSB) are reported to play a significant role in increasing the P efficiency of both native and applied P and improving the growth and yield of various crops (Khan et al, 2009).…”

“…Phosphorus (P) is the second important key plant nutrient which affects the overall growth of plants by influencing the key metabolic processes such as cell division and development, energy transport (ATP, ADP), signal transduction, macromolecular biosynthesis, photosynthesis and respiration (Shenoy and Kalagudi, 2005;Khan et al, 2009Khan et al, , 2014. Soils contain very little total P (0.02-0.5 % (w/w); Fernandez et al, 2007), of which only 0.1 % is available to plants (Zou et al, 1992).…”

Screening of PGPR Isolates for Plant Growth Promotion of Rosa damascena

“…PEPV12 showed significant increase in shoot length of spinach with respect to un-inoculated plants (Jiménez-Gómez et al, 2016). Several other studies also reported that plants showed superior morphological growth due to soil inoculation to increase supply of nitrogen, through BNF, (Togay et al, 2008;Ahmed et al, 2010;Khan et al, 2014).…”