PERMEABILITY OF THE CUTICLE OF VALLISNERIA-SPIRALIS TO CARBON-DIOXIDE AND OXYGEN

For most of their length, the leaves of the submerged aquatic angiosperm Vallisneria spiralis L. have isolated cuticular permeabilities of about 2.1-mu-m s-1 for carbon dioxide and 3.3-mu-m s-1 for oxygen, with no effect of orientation of the cuticle. Extraction of lipids from the cuticle increased the permeabilities to 7.7-mu-m s-1 and 9.6-mu-m s-1 for carbon dioxide and oxygen, respectively. Permeabilities were found to be lower at the leaf base and higher at the apex. At low oxygen concentrations, the uptake of oxygen by V. spiralis leaves from the medium may be limited by diffusion through the cuticle.