Leaf d. wt and the levels of soluble sugars and proteins show a two-phase development during leaf growth in Stevia rebaudiana. The initial large increases in leaf size are due mainly to water intake up to an area of around 9-10 cm2. Increases in absolute protein content were initially slow though in the second phase increased it rapidly with dry matter and soluble sugar content.In relative terms, however, the concentration of free sugars declined throughout leaf growth. The data indicate that leaf protein synthesis is most probably dependent upon a carbon supply from in situ photo synthesis which only becomes significant at 80 per cent of full leaf area. © 1980 Annals of Botany Company.454469474