Oxygen Diffusion in the Soil‐Plant System V. Oxygen Concentration and Temperature Effects on Oxygen Relations Predicted for Maize Roots1

Abstract

AbstractA model for steady state isothermal oxygen diffusion into a cylindrical root surrounded by a uniform water film, accounting for longitudinal oxygen flux through intercellular gas spaces, radial flux through the water film, and a concentration‐dependent respiratory oxygen sink, was used to assess effects of change in soil and root oxygen concentration and temperature on the oxygen relations of maize (Zea mays L.) roots.Increases in both root oxygen concentration at 5 cm from the tip and in soil oxygen concentration increased the root oxygen profile. Under conditions of high soil oxygen concentration and low root concentration oxygen diffused back along the root toward the shoot. Change in root oxygen concentration (0.05 to 0.15 ml/ml) at cm from the root tip had only a small effect on the oxygen concentration at the root tip, whereas an increase in soil oxygen concentration (0.05 to 0.15 ml/ml) increased the root tip oxygen concentration (0.02 to 0.07 ml/ml). Respiration rate of the root tip (1‐mm section) was closely dependent on soil oxygen supply and plant aeration had very little effect. Plant aeration contributed significantly to the respiration rate on a whole‐root basis. Mean root respiration rate increased with increase in soil and root oxygen concentration and also with increase in temperature. The root oxygen concentration profile decreased with rise in temperature associated with an increased respiratory oxygen demand. For mean respiration rate Q10 was less than 2 and decreased with increase in temperature.