SALT ABSORPTION AND METABOLISM 



83 



concentrations, inhibits salt uptake but stimulates cyanide-sensitive 

 respiration (Fig. 30). Lundegardh (1954) explained, however, that 

 only one of the cytochrome components (cytochrome b) may be 

 involved in salt uptake and this is inactivated by inhibitors of 

 phosphorylation, while cyanide-sensitive respiration continues 

 through other cytochromes by-passing cytochrome b. He observed 

 spectrophotometrically that cytochromes a and c continue to 

 function whereas b remains oxidized when wheat roots are immersed 



Table 7. The Ratios Sodium Absorbed Metabolically/Oxygen Involved in 

 Salt Respiration for Washed Slices of Red Beet Tissue Placed in Solutions 

 OF Sodium Chloride and Sodium Bicarbonate. 

 Metabolic absorption was estimated as the difference between uptake at the 

 high temperature (15 °C, or 25 °C) and at a low temperature (1-2 °C.). Salt 

 respiration was estimated as the difference between rates of oxygen absorption 

 in distilled water and in salt solution, at the high temperatures. 



(Sutcliffe, unpublished). 



in DNP at a concentration of 3xlO^^M. Inhibitors of protein 

 synthesis may block ion absorption without any apparent effect on 

 respiration (see pp. 88-9), but a detailed study of the possible 

 influence such substances have on the cytochromes has yet to be 

 made. 



{e) The maximum number of anions transported for each 

 molecule of oxygen consumed in salt respiration is 4 on the basis of 

 the Lundegardh hypothesis. However, evidence has now been 

 obtained with both plant and animal tissues that under favourable 

 conditions more than 4 ion pairs may be transported per oxygen 

 molecule consumed (see Sutcliffe and Hackett, 1957, also Table 7). 

 If this is true, an electrochemical mechanism must be at least 

 supplemented by another of higher efficiency. 



