Phosphate solubilization by organic anion excretion from rice (Oryza sativa L.) growing in aerobic soil |
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Authors: | Kirk GJD Santos EE Findenegg GR |
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Institution: | (1) International Rice Research Institute, PO Box 933, 1099 Manila, Philippines and FAX No;(2) Department of Soil Science and Plant Nutrition, Wageningen Agriculture University, PO Box 8005, 6700 EC Wageningen, The Netherlands |
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Abstract: | A mathematical model of P solubilization by organic anion excretion from roots is described and used to account for P solubilization
by rice (Oryza sativa L.) plants growing in aerobic soil. In previous experiments with rice in an aerobic, highly-weathered,
P-deficient soil, we found that the plants were able to solubilize P from an alkali-soluble pool and thereby increase their
P uptake. The solubilization could not be explained by pH changes nor by the release of phosphatases. In subsequent experiments
we found excretion of citrate from rice roots into nutrient solutions, and the synthesis and excretion of citrate tended to
increase under P starvation. The model allows for the diffusion of the organic anion away from a root, its decomposition by
soil microbes, its reaction with the soil in solubilizing P, and diffusion of the solubilized P back towards the root as well
as away from it. We calculated the rate of citrate excretion from rice roots growing in soil based on measured steady-state
citrate concentrations in the rhizosphere and calculated rates of decomposition. Calculations using these and other model
parameters obtained independently showed that the observed solubilization and increased P uptake by rice growing in soil could
be accounted for. A sensitivity analysis of the model is given.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | rhizosphere roots microbes interfaces modelling exudation |
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