Carboxylate concentrations in the rhizosphere of lateral roots of chickpea (Cicer arietinum) increase during plant development, but are not correlated with phosphorus status of soil or plants

The influence of soil P level and plant development on carboxylate concentrations in the rhizosphere of lateral roots of chickpea (Cicer arietinum) cultivars Heera. and Tyson were studied to investigate the relationship between carboxylate exudation and P acquisition by chickpea. Two chickpea cultivars were grown in soil supplied with 0-100 mug P g(-1). Plants were harvested four times during plant development. In two other experiments, carboxylate concentrations were measured along root sections, using plants grown in soil or in hydroponics. Carboxylate concentrations in the rhizosphere of lateral roots steadily increased with plant development for cv. Heera, but not for Tyson. Carboxylate concentrations increased with increasing distance from the root apex in soil. This increase might be due to accumulation, because an experiment with plants in hydroponics showed that older segments released at least as much carboxylates as younger segments. Carboxylate concentrations in the rhizosphere of chickpea appear to be developmentally controlled. Unlike some other plant species, there is no simple correlation with plant or soil P status.