Jones,D.L.(1998): Organic acids in the rhizosphere - a critical review. Plant and Soil, 205, 25-44.


 Organic acids, such as malate, citrate and oxalate, have been proposed to be involved in many processes operating in the rhizosphere, including nutrient acquisition and metal detoxification, alleviation of anaerobic stress in roots, mineral weathering and pathogen attraction. A full assessment of their role in these processes, however, cannot be determined unless the exact mechanisms of plant organic acid release and the fate of these compounds in the soil are more fully understood. This review therefore includes information on organic acid levels in plants (concentrations, compartmentalisation, spatial aspects, synthesis), plant efflux (passive versus active transport, theoretical versus experimental consideration), soil reactions (soil solution concentrations, sorption) and microbial considerations (mineralization). In summary, the release of organic acids from roots can operate by multiple mechanisms in response to a number of well-defined environmental stresses (e.g., Al, P and Fe stress, anoxia): These responses, however, are highly stress- and plant-species specific. In addition, this review indicates that the sorption of organic acids to the mineral phases and mineralisation by the soil's microbial biomass are critical to determining the effectiveness of organic acids in most rhizosphere processes.』


Organic acids in plants
 Root content
 Root release of organic acids
 Theoretical considerations
 Experimental considerations
 Organic acid release by calciole versus calcifuge plants
 Organic acid release under Fe deficiency
 Organic acid release under phosphorus deficiency
 Role of organic acids in aluminium detoxification
 Organic acid release by roots under other nutrient stresses
 Organic acid release by roots under oxygen stress
Do organic acids cause rhizosphere acidification ?
Organic acids in soil
 Soil solution concentrations
 Metal complexation reactions in the soil solution
 P, Mn and Fe mobilisation
 Organic acid sorption in soils
 Concentration gradients of organic acids in the rhizosphere
 Organic acids in mineral dissolution and pedogenic processes
Impact of the soil microbial biomass on organic acids