Nitrogen fixers fix atmospheric nitrogen in loose association with plant roots and also endophytically colonizes in the plant tissues. Nitrogen fixers convert atmospheric nitrogen gas into ammonium form and provide 30-50% of plants nitrogen requirements.
Phosphate solubilizers dissolve fixed phosphate into plant utilizable form. They produce organic acids, hormones and enzymes that help, in solubilisation of insoluble phosphates into plant utilizable form.
Plants require potassium ions (K+) for protein synthesis and for the opening and closing of stomata, which is regulated by proton pumps to make surrounding guard cells either turgid or flaccid. A deficiency of potassium ions can impair a plant's ability to maintain these processes. Potassium also functions in other physiological processes such as photosynthesis, protein synthesis and activation of some enzymes.