730 



S. Tojizig and E. Marre 



ID 



MOLAR CONCN. OF DHA xlO 



Fig. 2. The effects of dehydroascorbic acid (DHA) on phosphorylation conpled to 

 malate and succinate oxidation of mitochondria from pea internode tissues (Forti, 2). 



In addition, the decrease of the reduced to oxidized glutathione 

 ratio in the AA treated tissues appeared fully consistent with the hy- 

 pothesis that the real inhibiting agent is DHA, as the enzyme gluta- 

 thione-dehydroascorbic acid reductase was found present in the Avena 

 coleoptile and pea internode tissues (11, 27). 



THE EFFECTS OF AUXIN ON ASCORBIC ACID 



METABOLISM 



According to the working hypothesis suggested by the above- 

 mentioned results, AA induced inhibition of growth and respiration 

 might be conveniently interpreted as due to the rise of the DHA:AA 

 ratio, followed by a corresponding decrease of the reduced to oxidized 

 glutathione ratio, and by secondary effects such as changes of the 

 physico-chemical state of cytoplasm and the activity of enzyme sys- 



Table 3. The effects of increasing auxin concentrations on AA and DHA contents 

 in pea internode segments (23). 



