Plant-mediated processess to acquire nutrients: nitrogen uptake by rice plants

Abstract

The ways in which root-soil interactions can control nutrient acquisition by plants is illustrated by reference to the N nutrition of rice. Model calculations and experiments are used to assess how uptake is affected by root properties and N transport through the soil. Measurements of the kinetics of N absorption and assimilation and their regulation, and of interactions between NH ⁺₄ and NO ⁻₃ nutrition, are described. It is shown that uptake of N from the soil—as opposed to N in ricefield floodwater which can be absorbed very rapidly but is otherwise lost by gaseous emission—will often be limited by root uptake properties. Rice roots are particularly efficient in absorbing and assimilating NO ⁻₃ , and NH ⁺₄ absorption and assimilation are stimulated by NO ⁻₃ . The uptake of NO ⁻₃ formed in the rice rhizosphere by root-released O₂ may be more important than previously thought, with beneficial consequences for rice growth. Other root-induced changes in the rice rhizosphere and their consequences are discussed.