The article "Organic Acids in the Rhizosphere – A Critical Review" by David L. Jones provides a comprehensive overview of the role of organic acids, such as malate, citrate, and oxalate, in various processes within the rhizosphere. These acids are implicated in nutrient acquisition, metal detoxification, alleviation of anaerobic stress, mineral weathering, and pathogen attraction. The review highlights the importance of understanding the mechanisms of plant organic acid release and their fate in the soil. Key points include: 1. **Plant Organic Acid Levels**: Roots contain various organic acids, with lactate, acetate, oxalate, succinate, fumarate, malate, citrate, isocitrate, and aconitate being the primary anions. The concentration of these acids is influenced by the plant's C fixation type, nutritional status, and age. Typically, the total concentration of organic acids in roots is around 10–20 mM. 2. **Plant Efflux**: The release of organic acids from roots can occur through multiple mechanisms in response to environmental stresses such as aluminum (Al), phosphorus (P), and iron (Fe) stress, and anoxia. However, these responses are highly specific to the stress and plant species. 3. **Soil Reactions**: The sorption of organic acids to the mineral phase and mineralization by soil microbial biomass are crucial for their effectiveness in rhizosphere processes. Soil solution concentrations and sorption are important factors in determining the fate of these acids. 4. **Microbial Considerations**: Mineralization by the soil's microbial biomass is a critical process that affects the availability and effectiveness of organic acids in the rhizosphere. The review emphasizes the complexity of organic acid reactions in soil and the need for a better understanding of the mechanisms involved. It also discusses the spatial distribution and compartmentalization of organic acids within plant roots, noting that the concentration gradient between the cytosol and soil solution is key to determining efflux rates.The article "Organic Acids in the Rhizosphere – A Critical Review" by David L. Jones provides a comprehensive overview of the role of organic acids, such as malate, citrate, and oxalate, in various processes within the rhizosphere. These acids are implicated in nutrient acquisition, metal detoxification, alleviation of anaerobic stress, mineral weathering, and pathogen attraction. The review highlights the importance of understanding the mechanisms of plant organic acid release and their fate in the soil. Key points include: 1. **Plant Organic Acid Levels**: Roots contain various organic acids, with lactate, acetate, oxalate, succinate, fumarate, malate, citrate, isocitrate, and aconitate being the primary anions. The concentration of these acids is influenced by the plant's C fixation type, nutritional status, and age. Typically, the total concentration of organic acids in roots is around 10–20 mM. 2. **Plant Efflux**: The release of organic acids from roots can occur through multiple mechanisms in response to environmental stresses such as aluminum (Al), phosphorus (P), and iron (Fe) stress, and anoxia. However, these responses are highly specific to the stress and plant species. 3. **Soil Reactions**: The sorption of organic acids to the mineral phase and mineralization by soil microbial biomass are crucial for their effectiveness in rhizosphere processes. Soil solution concentrations and sorption are important factors in determining the fate of these acids. 4. **Microbial Considerations**: Mineralization by the soil's microbial biomass is a critical process that affects the availability and effectiveness of organic acids in the rhizosphere. The review emphasizes the complexity of organic acid reactions in soil and the need for a better understanding of the mechanisms involved. It also discusses the spatial distribution and compartmentalization of organic acids within plant roots, noting that the concentration gradient between the cytosol and soil solution is key to determining efflux rates.