A plant's perception of growth-promoting bacteria (PGPR) and their metabolites is a critical area of research in plant science. This review discusses the primary evidence of how PGPR and their metabolites modify plant ecophysiology, emphasizing the importance of measuring photosynthetic activity using leaf gas exchange and determining the correct timing for monitoring plant responses based on experimental objectives. The study highlights the challenges and future directions for scientists working on PGPR-plant interactions to better understand and utilize the potential of microorganisms in improving plant value. The review begins by discussing the importance of PGPR in supporting plant growth, particularly under biotic and abiotic stress. It highlights the role of PGPR in enhancing plant biomass, root architecture, leaf area, and specific metabolite accumulation. The study also emphasizes the need to consider energy balance, including photosynthesis and respiration, in understanding PGPR effects on plant growth. The review then discusses the classification of PGPR based on classical and ecophysiological studies, as well as the proposed classification of PGPR. It also outlines the main topics addressed by research articles and reviews, including the isolation of PGPR and their properties and potential role in alleviating plant stress. The review discusses the importance of using leaf gas exchange measurements to assess the modifications triggered by PGPR and their metabolites on different aspects of the photosynthetic process. It also highlights the gaps in the literature and identifies challenges to provide future directions for scientists working on bacteria-plant interactions to exploit the potential of PGP microorganisms in improving plant value. The review also discusses plant growth in a changing environment, highlighting the cellular mechanisms involved in division and expansion, and the factors that influence plant development. It discusses the role of phytohormones in plant growth and the effects of various stress conditions on plant growth. The review then discusses the effects of PGPR on plant growth, including their ability to improve plant nutritional status, increase tolerance to abiotic stresses, prevent and control pathogen infections, and mitigate the negative impact of contaminants. It also discusses the role of PGPR in biocontrol, preventing agricultural losses due to pathogen infections, and their ability to enhance plant resistance by improving plant growth rate. The review concludes by emphasizing the importance of plant ecophysiology as a tool to assess plant's perception of PGPR under non-stressed and stressed growth conditions. It highlights the need to measure parameters such as chlorophyll fluorescence, photosynthetic activity, and leaf gas exchange to understand the mechanisms that drive the photosynthetic and growth processes in the presence of beneficial microorganisms. The review also discusses the importance of determining the time scale that allows the detection of changes induced by PGPR on plant ecophysiological performance.A plant's perception of growth-promoting bacteria (PGPR) and their metabolites is a critical area of research in plant science. This review discusses the primary evidence of how PGPR and their metabolites modify plant ecophysiology, emphasizing the importance of measuring photosynthetic activity using leaf gas exchange and determining the correct timing for monitoring plant responses based on experimental objectives. The study highlights the challenges and future directions for scientists working on PGPR-plant interactions to better understand and utilize the potential of microorganisms in improving plant value. The review begins by discussing the importance of PGPR in supporting plant growth, particularly under biotic and abiotic stress. It highlights the role of PGPR in enhancing plant biomass, root architecture, leaf area, and specific metabolite accumulation. The study also emphasizes the need to consider energy balance, including photosynthesis and respiration, in understanding PGPR effects on plant growth. The review then discusses the classification of PGPR based on classical and ecophysiological studies, as well as the proposed classification of PGPR. It also outlines the main topics addressed by research articles and reviews, including the isolation of PGPR and their properties and potential role in alleviating plant stress. The review discusses the importance of using leaf gas exchange measurements to assess the modifications triggered by PGPR and their metabolites on different aspects of the photosynthetic process. It also highlights the gaps in the literature and identifies challenges to provide future directions for scientists working on bacteria-plant interactions to exploit the potential of PGP microorganisms in improving plant value. The review also discusses plant growth in a changing environment, highlighting the cellular mechanisms involved in division and expansion, and the factors that influence plant development. It discusses the role of phytohormones in plant growth and the effects of various stress conditions on plant growth. The review then discusses the effects of PGPR on plant growth, including their ability to improve plant nutritional status, increase tolerance to abiotic stresses, prevent and control pathogen infections, and mitigate the negative impact of contaminants. It also discusses the role of PGPR in biocontrol, preventing agricultural losses due to pathogen infections, and their ability to enhance plant resistance by improving plant growth rate. The review concludes by emphasizing the importance of plant ecophysiology as a tool to assess plant's perception of PGPR under non-stressed and stressed growth conditions. It highlights the need to measure parameters such as chlorophyll fluorescence, photosynthetic activity, and leaf gas exchange to understand the mechanisms that drive the photosynthetic and growth processes in the presence of beneficial microorganisms. The review also discusses the importance of determining the time scale that allows the detection of changes induced by PGPR on plant ecophysiological performance.