Abstract

Light energy is captured and used to convert water, carbon dioxide, and minerals into oxygen and energy-rich organic compounds through photosynthesis, and this process is of high importance in the maintenance of life on Earth. On the other hand, plant growth-promoting rhizobacteria (PGPR) are a diverse group of bacteria that can be found in the rhizosphere, on root surfaces, and in association with roots. PGPR affect the physiology of plants to attenuate to some degree the stressful effects of drought, salt, UV, and a combination of high CO2 content and low atmospheric pressure. PGPR also increase the photosynthetic capacity via photochemical quenching and CO2 assimilation rate. A deep study on how PGPR secondary metabolites modulate the plant photosynthesis is performed. PGPR increase the plant photosynthesis, chlorophyll contents, stomatal conductance, transpiration rate, and photosystem II efficiency of plants even in stressed conditions.