Permeability of Vicia Faba Root Segments to Water as Measured by Diffusion of Deuterium Hydroxide.

Abstract
The permeability of Vicia faba roots to water was measured by the rate of diffusion of deuterium hydroxide (DHO). The half time DHO diffusion into living root segments was 0.6 minute. The half time for roots killed by dinitrophenol (DNP) was 0.2 minute and for roots killed by immersion in hot water was 01 minute. A lower nonlethal concentration of DNP decreased root permeability, the average half time being 1.1 minutes. The results of this study indicate that the cytoplasm rather than the cell walls constitutes the principal resistance to water movement in V. faba roots. These results differ from those obtained in previous studies with Avena coleoptiles in which permeability was little increased by killing the tissue, indicating that most of the resistance to water movement exists in the cell walls of Avena coleoptiles.