Microbial Phytohormone Production as Signal for Plant Growth Promotion

Soil microbes release substances that directly or indirectly enhance plant growth promotion. The commonly recognized plant growth promotion mechanisms are production of phytohormones, suppression of diseases, biocontrol, and production of volatile signal compounds. Beneficial bacteria produce phytohormones such as indole-3-acetic acid (IAA), gibberellins, cytokinin, ethylene, and salicylic acid that promote plant growth and development. A study revealed that bacteria isolated from the rhizosphere soils of Pteris vittata in an ex-tin mining site produce phytohormones as part of the chemical signals that promote the plant’s growth. From the result, four best isolates identified as Enterobacter chengduensis 2P5 (CCB-MBL 5011), E. sichuanensis 3P19 (CCB-MBL5012), Bacillus paramycoides 3P20 (CCB-MBL5013), and E. sichuanensis 5P7 (CCB-MBL5015) produce phytohormones which may enhance plant growth and development in the ex-tin mining areas. Finally, exploring plant hormones and their uses is one of the future study directions in agricultural, environmental, botanical, and microbiological fields.