Sugar and Ion Transport in Isolated Onion Epidermis

Abstract

The apparent unidireotional transport of sugars and ions in isolated onion epidermis was shown to be due to the presenoe of a outiole on the outer surfaoe of the epidermis. The outiole probably is partially permeable for ions and impermeable for hexoses. Sugar transport aoross the inner surfaoe of isolated epidermis had a temperature ooeffioient (k20°C/klOoC) of 2·4, the oorresponding activation energy was 14·5 koal/mole, and the permeability coeffioient was approximately 10-8 cm/sec. Sugar transport was not inhibited by oarbonyl oyanide m-chlorophenylhydrazone, potassium cyanide, or sodium azide.