Radial movement of oxygen in plant roots.

The radial movement of oxygen in excised corn and jack bean roots was measured with a platinum wire electrode embedded in the root tissue. Measurements were made with the roots exposed to air and with the roots immersed in nutrient solution in the presence and absence of millimolar sodium azide. Effective rates of oxygen diffusion in the root tissue were also measured from 5 to 30 C and compared to the respiration rates of similar root segments over the same temperature range. Under conditions which allow the roots to exude freely, the interior of the root operates under an oxygen deficit. Inhibition of respiratory oxygen uptake by low temperature or azide treatment increased the flux of oxygen to the root interior.