The Diffusion Resistance and Water Status of Leaves ofBeta vulgaris

Abstract

Pot-grown sugar-beet plants were deprived of water in two experiments until they wilted completely. Leaf resistance to water-vapour transfer was measured directly with a diffusion porometer and compared with values calculated from measurements of transpiration. There was good agreement between the two estimates. Leaf turgor-pressure decreased only gradually due, apparently, to an increase in tissue-solute concentration with increasing water deficit. Relationships between leaf water potential, soil water potential, and leaf resistance were established and the effective control of transpiration by small changes in leaf resistance was clearly demonstrated.