Abstract
Organic acids secreted from plant roots play important roles in various biological processes including nutrient acquisition, metal detoxification, and pathogen attraction. The secretion of organic acids may be affected by various conditions such as plant growth stage, nutrient deficiency, and abiotic stress. For example, when white lupin (Lupinus albus L.) is exposed to phosphorus (P)-deficient conditions, the secretion of citrate acid from its proteoid roots significantly increases ( Neumann et al., 1999 ). This protocol describes a method for the collection and measurement of the efflux of organic acids (oxalate, malate, and citrate) from the roots of rice cultivar Nipponbare ('Nip') under different nitrogen forms (NH4 + and NO3-), together with different P supply (+P and -P) conditions.