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Oxygen Uptake by Corn Roots in Flowing and Stirred Solution Cultures¹

A model incorporating the mechanism of the O₂ uptake process as described by the Hill equation and mass flow mechanisms is given for both steady-state and time-dependent cases. The two versions of the model were used to study O₂ uptake. Computed results of the steady-state model indicated that the higher the water flux density the less O₂ depletion there was in relation to distance from the aeration point. The hypothesis raised by these theoretical results is that availability of O₂ in aqueous media may be influenced by water flux density. The objectives of this research were therefore to test the above hypothesis experimentally and to compare measured and calculated results with the time-dependent model. The experiments were based on a hydroponic system with corn plants (Zea mays, ‘Jubilee’) placed on flowing plates. At a certain point air was pumped continuously. Measurements of O₂ concentration as a function of distance from this point were taken at various velocities. The test of the second model was made in a container with a stirred-solution culture. Calculated and experimental results for the steady-state model agreed with each other and suggested that the flow rate of the solution is an important factor in controlling O₂ concentration along the channels. For a homogenous solution (i.e., O₂ concentration which is not affected by the distance from the aerated point), the time-dependent version of this model gave satisfactory results when compared to measured values on a quantitative basis. Qualitatively, however, the agreement was not so good.

Key Words: Mathematical model • Hydroponics

² Molecular scientist, soil scientist, and plant physiologist, respectively.

Received for publication June 30, 1980.