SALT TOLERANCE 



151 



capacity in relation to transpiration, tend to exhibit poor salt 

 tolerance. A low shoot-to-root ratio seems to be one of the adapt- 

 ations of some halophytes to saline habitats. As may be expected, 

 conditions leading to high transpiration, e.g. high light intensity, 

 and low humidity, may induce salt damage at concentrations which 

 have no deleterious effects under conditions favouring low rates of 



Table 16. Salt Tolerance (Osmotic pressure of Sodium Chloride gfving 



50 per cent Reduced Growth) and the Osmotic Pressure of the Expressed 



Sap from the Leaves and Roots, of Various Species, placed with their 



Roots in Media of Different Osmotic Pressures. 



(Abbreviated from Bernstein and Hayward, 1958). 



transpiration. Finally, slow-growing species tend on the whole to 

 be more salt-tolerant than those which grow rapidly. 



The specific inhibitory effects on growth of ions at high con- 

 centrations are still not properly understood. Interference with the 

 absorption of an essential element or with its functioning in the 

 cytoplasm are among the possible causes. A high concentration of 

 salt may adversely affect the activity of cytoplasm through an influence 

 upon hydration and the effect of a particular ion at a high con- 

 centration can sometimes be counterbalanced by the presence of 



