SALT RELATIONS OF VASCULAR PLANTS 



115 



equal amount of salt was transferred into the shoots under the 

 various conditions, thus disposing of the objection that uptake by 

 these plants was mainly due to accumulation in the roots. Some 

 increase of salt absorption at high transpiration rates was obtained 

 with plants which had a high initial salt content. The stimulation 

 resulting from illumination was attributed to promotion of photo- 

 synthesis rather than to increased transpiration, on the assumption 

 that sugar content limits uptake in high salt plants which are 

 characteristically low in carbohydrates. In addition, the high 



Table 9. Influence of Transpiration on Absorption and Translocation 



OF Salts by Barley Plants. 

 (Data of Broyer and Hoagland 1943). 



concentration of salt in the xylem sap of high-salt plants, may 

 serve to depress further absorption of ions at low transpiration 

 rates (see below). 



A number of other investigators have observed stimulation of 

 salt absorption with increasing transpiration rates, but in most 

 cases the two changes are by no means proportionate, and different 

 ions are frequently affected differently (Table 10). Schmidt (1936) 

 claimed that a linear relationship exists between water absorption 

 and that of various ions in young plants of Sanchezia nobilis. 

 Regression lines plotted from his results, except those for nitrate, 



