Growth Promotion of Plants, Especially Rice, by Phosphate Solubilizing Microbes

Phosphorus (P) is the second important macronutrient after nitrogen and important at all growth
stages of plants including rice. It is an important constituent of macromolecules like DNA, RNA, ATP,
phospholipids etc. and a major repository of chemical energy. P availability is optimum at neutral pH.
Phosphate solubilizing microbes (PSM) viz. Bacillus, Azotobacter, Pseudomonas, Aspergillus spp.
recycle the nutrients like N, P, C, K, S, Fe etc. and promote growth of plants. The endophytes
like Rhizobium, Azospirillum, Pseudomonas spp., epiphytes like Rhizobium, Pantoea spp.,
rhizospheric organisms like Bacillus, Pseudomonas, Erwinia spp. and entomopathogens viz.
Beauveria, Metarhizium, Nomuraea spp. mineralize insoluble P to make accessibility to plants. Soil
enzymes also solubilize organic phosphates (OP) to available forms. Oxidation of glucose to gluconic
acid, production of organic and inorganic acids, ammonia, H2S etc. are major mechanisms for P
mineralization by microbes. So, phosphate solubilizing microbes would be efficient biofertilizers as
they promote plant growth, improve soil properties and prevent plant pathogens without any harsh
effect on the environment.