Oxygen Diffusion in the Soil-Plant System III. Oxygen Concentration Profiles, Respiration Rates, and the Significance of Plant Aeration Predicted for Maize Roots
- R. J. Luxmoore,
- L. H. Stolzy and
- J. Letey
Oxygen concentration profiles, mean respiration rates, and the percent plant aeration estimates (proportion of respired oxygen diffusing from the atmosphere via gas spaces in the plant) were obtained from an analysis of steady state oxygen diffusion in maize (Zea mays L.) root models under simulated field conditions.
An increase in root radius and in water film thickness as occurs after rainfall or irrigation induced a decrease in oxygen concentration within the root, a decrease in mean respiration rate, and an increase in percent plant aeration (PPA). An increase in root length reduced both mean respiration rate and PPA. The mean respiration rates calculated for the various models were about half of the maximum rate for mature root tissue, indicating that oxygen concentration is the main factor limiting respiration rate under the simulated field conditions.
Plant aeration increased markedly with increase in root porosity and this was accompanied by a higher oxygen concentration profile in the root and a small increase in mean respiration rate. Changes in the respiration or root wall permeability had minor effects on PPA.
Under conditions which simulate the growth of adventitious roots of maize (0.05-cm root radius and 20-cm root length), PPA is 34% for a well aerated soil (0.01-cm water film) and 42% for a soil which is oxygen deficient (0.05-cm water film). Plant aeration is thus predicted to be a significant factor in the oxygen relations of maize roots. For a given root system, the gas-filled porosity and the thickness of the water film around the root have the greatest influence on this process. Soil aeration is important in the oxygen supply to the lower root and root tip regions and thus has a critical effect on continuing plant growth and development.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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