SOME OBSERVATIONS ON OXYGEN TRANSPORT IN CONIFER SEEDLINGS

Abstract

SummaryThe diffusive flux of oxygen from the roots of intact conifer seedlings was measured by a polarographic technique. With an anaerobic solution bathing the roots maintained at 23° C and with their aerial parts in air, flux rates were appreciable from eight of the twenty‐five seedlings tested. When the aerial parts were placed in oxygen, there was a large increase in flux from each pine seedling. While their general response was barely measurable, a significant but much smaller increase occurred from eight of the spruce. Oxygen transport through the plants appeared to be by diffusion chiefly in the gas phase and significant flux rates from the roots with aerial parts in air might indicate some capacity for wet soil tolerance in the seedlings concerned.When the external concentration of oxygen was increased five‐fold there was a disproportionate increase in oxygen flux from pine roots indicating that respiration in the plants might be affecting the flux rates. By cooling the bathing medium to 30 C a further demonstration of the respiratory effect‐a large increase in flux rate‐was obtained. With respiration reduced by cooling, the flux rates from the pine seedlings increased approximately five‐fold for a five‐fold increase in the external oxygen concentration. Cooling did not induce any pronounced response from the spruce seedlings.Internal diffusional resistance and oxygen leakage from the sub‐apical parts of the roots may account for the absence of high apical flux rates in the pines and the extremely low readings recorded for the spruce seedlings.