WATER RELATIONS OF SPECIES: COMPARISONS 



297 



tolerance to the same loss of turgidity in the leaf; secondly, through 

 differences in the maintenance of leaf turgor attributable to differences in 

 the abihty to take up water from soil of increasing SMT; and thirdly, 

 through differences in maintenance of leaf turgor attributable to differences 

 in the ability to restrict water loss from the leaves, for example, by stomatal 

 closure and a subsequent low rate of cuticular transpiration. This third 



100- 



so- 



_60- 



O 



z 



AO- 



20- 



Fig. 3. Filipaidiila vulgaris. The effect of soil moisture tension on leaf elongation. 

 (1-18 December 1959.) Each curve represents a single leaf Container numbers are 

 at the ends of the curves. Plants in container i vi^ere not subjected to drying-out. 

 Soil moisture tensions (atm) for containers 2 and 3 are shown beside corresponding 

 points on the curves. W: see Fig. 2. 



possibiHty may result in maintenance of leaf turgor only at the expense of 

 maintenance of the photosynthetic rate. 



The relation between leaf water content and SMT was compared for 

 the four species with the object of determining whether the greater effect 

 of increasing SMT on the growth rate of Saxifraga hypnoides and Primus 

 padus, as compared with Filipendula vulgaris and Thelycrania sanguinea, was 



