The Importance of Phytohormones and Microbes in Biofertilizers

Plant growth is dependent on meristems where cell proliferations (cell division and growth) give rise to new plant structures and allow the plant to increase in size. We provided scientific linkages and evidence to show that the growth promoting factors in biofertilizers regulating cell proliferation and ultimately modulating plant growth and development are phytohormones. The known biological functions of phytohormones (cytokinins, auxins, gibberellins, etc.) are in tandem with the observed physiological characteristics and crop yield of plants. When light, water and mineral nutrients are not limiting, phytohormones especially cytokinins, in biofertilizers help to drive plant growth by progressing faster through the various plant cell cycle checkpoints leading to the production of more cells. In the soil matrices, PGPRs (Plant Growth Promoting Rhizobacteria) have the ability to promote plant growth via various mechanisms such as nitrogen fixation, phosphorus and zinc solubilization. Some PGPRs secrete phytohormones, especially cytokinins, and can be cultured and developed into a biofertilizer. In the near future, a hybrid approach of combining organic and conventional fertilization regimes will be the likely scenario as we have achieved a better understanding of plant growth and development through the regulatory controls on the cell proliferation processes by phytohormones and mineral nutrients delivered by fertilizers. The futuristic green biofertilizer should come in the form of granules in which the active plant growth promoting and soil improving substances and/or suitable microbes, with carefully selected mineral nutrients, are embedded in the packing materials giving slow and sustained release over a desired period.