Ascorbic Acid As a Growth Hormone 



ni 



THE EFFECTS OF ASCORBIC ACID ON PROCESSES 

 DIFFERENT FROM GROWTH 



Plasma Viscosity 



Plasma viscosity, measured as change of time of plasmolysis in 

 hypertonic solutions, was shown by Tonzig and Trezzi (23) to be de- 

 creased by AA treatment under a number of experimental conditions 

 and in quite different plant materials. Also the water-holding capacity 

 markedly decreased in the AA treated tissues (22). This suggested that 

 changes of the physico-chemical state of the cytoplasm could play an 

 important role in mediating the effects of AA on water uptake and 

 on growth (18, 22). 



Respiration 



The oxygen uptake of pea internode segments was markedly in- 

 hibited by the presence in the medium of AA at concentrations higher 

 than 3 X 10"^ ^- At concentrations which inhibit growth by 40 to 50 

 per cent, an apparent 20 per cent decrease in respiration rate was 

 observed; this value rose to above 35 per cent inhibition when the 

 data were corrected for the Go uptake due to the enzymatic oxidation 

 of AA in the medium (Figure 1). A very strong AA oxidase activity ap- 

 peared to develop at the cut surfaces of the segments (16, 25) (Table 1). 



300 



X 



en 



UJ 



CNJ 



O 



200 - 



100 



120 



MINUTES 



Fig. 1. The effects of ascorbic acid treatment on O^ uptake of pea internocie seg- 

 ments. A, control; B, ascorbic acid (2 X 10"^ M) corrected for autooxidation only; 

 C, ascorbic acid (2 X 10"^ M) corrected for autooxidation and enzymatic oxidation. 



