Mechanical Impedance Effects on Oxygen Uptake and Porosity of Drybean Roots
1981
Schumacher, T. E. | Smucker, A. J. M.
Low oxygen concentrations and mechanical impedance are two components of soil compaction often implicated in the reduction of crop yields. The relative importance of these two stresses to the root system has not been thoroughly assessed. A system was developed to study the effect of mechanical impedance on root respiration and morphology. Oxygen uptake, by intact plant root systems subjected to three levels of mechanical impedance, was determined polarographically by measuring the oxygen concentration of nutrient solutions before and after flowing through a root media of 1 mm, 3 mm, or no glass beads. Oxygen uptake rates by drybean (Phaseolus vulgaris L.) roots were independent of solution flow rates ≥ 6.0 ml/min⁻¹ when inlet pO₂ was 0.21 atm. Mechanical impedance reduced dry weight, fresh weight, volume, and length of roots after 8 days of treatment. Dry matter percentage of mechanically impeded roots was greater than the control. Roots subjected to mechanical impedance were deformed, branched more frequently, less porous, and consumed more oxygen per unit fresh weight. It is suggested that a greater oxygen supply may be required at the root surface to prevent anoxia in mechanically impeded roots.
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