Metabolism and mode of action 



preference. We are now endeavouring to find which of these fractions re- 

 sponds inductively to lAA, both with regard to lAA destruction and to 

 lignin biosynthesis. 



SUMMARY 



What emerges from these studies is a tentative picture of the ways in which 

 the plant growth hormone, indoleacetic acid, may be responsible not only 

 for the growth of a plant cell, but also for the cessation of growth, and for the 

 differentiation of some cells into lignified elements. In the latter two processes, 

 the metabolism of peroxides seems to play a major role. 



REFERENCES 



Andreae, W. a., and Andreae, S. R. (1953). Studies on indoleacetic acid meta- 

 bolism. I. Canad. J. Bot. 31, 426. 



Beadle, G. W., Mitchell, H. K., and Nyc, J. F. (1947). Kynurenine as an inter- 

 mediate in the formation of nicotinic acid from tryptophane by Neurospora. Proc. 

 Nat. Acad. Sci., Wash. 33, 155. 



Galston, a. W., and Baker, R. S. (1951). Studies on the physiology of light action. 

 III. Light activation of a flavoprotein enzyme by reversal of a naturally-occurring 

 inhibition. Amer. J. Bot. 38, 190. 



Galston, A. W., and Dalberg, L. (1954). The adaptive formation and physio- 

 logical significance of indoleacetic acid oxidase. Amer. J. Bot. 41, 373. 



Galston, A. W., Bonner, J., and Baker, R. S. (1953). Flavoprotein and peroxidase 

 as components of the indoleacetic acid oxidase system of peas. Arch. Biochem. 

 Biophys. 42, 456. 



GoLDACRE, P. L. (1951). Hydrogen peroxide in the enzymic oxidation of hetero- 

 auxin. Aust. J. Sci. Res. B4, 293. 



GoLDACRE, P. L., Galston, A. W., and Weintraub, R. L. (1953). The effect of 

 substituted phenols on the activity of the indoleacetic acid oxidase of peas. Arch. 

 Biochem. Biophys. 43, 358. 



GoRTNER, W. A., and Kent, M. (1953). Indoleacetic acid oxidase and an inhibitor 

 in pineapple tissue. J. biol. Chetn. 204, 593. 



Jacobs, W. P. (1952). The role of auxin in differentiation of xylem around a wound. 

 Amer. J. Bot. 39,3^1. 



Jensen, W. A. (1955). The induction of peroxidase activity by indoleacetic acid. II. 

 Histochemical localization. Plant Physiol. 30, No. 5, 426. 



Jermyn, M. a., and Thomas, R. (1954). Multiple components in horseradish root 

 peroxidase. Biochem. J. 56, 631. 



Kondo, K., and Morita, Y. (1952). Phytoperoxidase II. Bull. Res. Inst. Food Sci., 

 Kyoto Univ. 10, 33. 



Larsen, P. (1951). Formation, occurrence and inactivation of growth substances. 

 Ann. Rev. PL Physiol. 2, 169. 



LocKHART, J. (1955). The role of 2 :4-dichlorophenol in the destruction of indole- 

 acetic acid by peroxidase. Plant Physiol. 30, 86. 



Manning, D. T., and Galston, A. W. (1955). On the nature of the enzymatically 

 catalysed oxidation products of indole-acetic acid. Plant Physiol. 30, 225. 



PiLET, P. E., and Galston, A. W. (1955). Auxin destruction, peroxidase activity 

 and peroxide genesis in the roots of^ Lens cidinaris. Physiol. Plant. 8, 888. 



Platt R. S., Jr. (1954). The inactivation of auxin in normal and tumorous tissues. 

 Ann. Biol. 30, 89. 



SEquEiRA, L., and Steeves, T. (1954). Auxin inacdvation and its relation to leaf drop 

 caused by the fungus Omphalia flavida. Plant Physiol. 29, 11. 



232 



