734 5. Tonzig and E. Marre 



21. Tonzig, S., and Trezzi, F. Ricerche sulla fisiologia dell'acido ascorbico. IV. 

 L'acido ascorbico e le curvature d'accrcscimento. Xuovo Gior. Bot. Ital. 57: 549- 

 563. 1950. 



22. , and Trezzi, F. Ricerche sulla fisiologia dell'acido ascorbico. VII. Azione 



dell'acido indol-3-acetico e dell'acido ascorbico sull'assunzione e sulla perdita 

 dacqua da parte di tessuti vegetali. Atti. Accad. Naz. Lincei Rend. 16: 434- 

 443. 1954. 



23. , and Trezzi, F. Ricerche sull'azione deH'acido indol-3-acetico. Atti. 



Accad. Naz. Lincei Rend. 16: 603-610, 695-702. 1954. 



24. , and Trezzi, F. Ricerche sulla fisiologia dell'acido ascorbico. XI. Mec- 



canismo competitive dell'interazione acido ascorbico-acido indolacetico. Atti. 

 Accad. Naz. Lincei Rend. 17: 324-331. 1954. 



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 nientahiiente indotte del rapporto AA/DHA e corrispondenti variazioni della 

 crescita e dell'attivita respiratoria di seginenti di fusto di Pisello. Atti. Accad. 

 Naz. Lincei Rend. 21: 220-228, 323-328. 1956. 



26. Wagenknecht, A. C, Riker, A. J., Allen, T. C, and Burris, R. H. Plant growth 

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 38: 550-554. 1951. 



27. Yamaguchi, M., and Joslyn, M. A. Investigations of ascorbic acid dehydrogenase 

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DISCUSSION 



Dr. Vlitos: I wonder if Dr. Marre has any recent information on 

 the possible role of ascorbigen? 



Dr. Marre: 1 don't have any direct information. The recent find- 

 ings of Prochazka could be of considerable importance in this regard, 

 especially if it were shown that ascorbigen is generally present in 

 higher plants and not only in Cruciferae. If a derivative of auxin 

 could bind with a precursor or a derivative of ascorbic acid, the 

 compound thus formed could possibly interact witii some enzyme 

 system involved in the oxidation or reduction of ascorbic acid. This 

 could help in understanding the effect of auxin on the reduced to 

 oxidized ascorbic acid ratio in vivo and also the inhibiting action of 

 auxin on ascorbic acid oxidase in vitro which has been reported in 

 different laboratories. This in vitro effect is poorly reproducible, so 

 that it seems more probable that it is due to some derivative of lA.A. 

 formed in the cell-free preparations than to piue auxin. But, of course, 

 at the present time this is just something between a working hypothesis 

 and pure speculation. 



