**4. The role of cyanobacteria in plant improvement**

 Cyanobacteria play an important role in improving plant growth and crop production. They are good bio-fertilizers, enhance solubilization and mobility of nutrients, and increase essential microelements in soil that are necessary for ion uptake, as well as stimulate plant growth due to their ability to produce bioactive compounds, such as phytohormones and other plant growth regulator substances, such as amino acids and polysaccharides ( **Figure 3** ).
