214 



The Distribution of Oxydases in Plants and their Role in the 

 Formation of Pigments, 

 By Frederick Keeble, Sc.D., Professor of Botany, University College, 

 Reading, and E. Frankland Armstrong, Ph.D., D.Sc. 



(Communicated by W. Bateson, F.R.S. Received March 15, — Read 

 May 2, 1912.) 



Whereas our knowledge of the mode of inheritance of flower colour has 

 made rapid and sure advance of recent years, our understanding of the 

 chemistry of the process of pigment formation in flowers is still uncertain and 

 incomplete. 



The researches of Miss Wheldale (1911) on flower-pigments and of Gortner 

 and others on animal-pigments have confirmed and extended the conclusions 

 of earlier workers, and it may now he regarded as an established fact that the 

 formation of pigment in plants and in animals is due to the action of an 

 oxydase on a more or less colourless chromogen. 



According to the experiments of Gortner (1911) the superficial pigmenta- 

 tion of various insects is the outcome of the action of tyrosinase on the 

 chromogen tyrosin. As a result of that action a black pigment, melanin, is 

 produced. Gortner has shown moreover that this reaction may be inhibited 

 by certain phenolic compounds such as phloroglucinol, orcinol and resorcinol. 

 These dihydroxyphenols Gortner describes as anti-enzymes and he attributes 

 the phenomenon of dominant whiteness, that is the suppression of pigment- 

 formation in tissues, believed, by reason of their mode of colour-inheritance, 

 to contain both chromogen and oxydase, to the presence — local or general — 

 of these anti-bodies. 



Miss Wheldale has obtained evidence that pigment formation in flowers 

 is consequent upon the interaction of an oxydase and a chromogen 

 and has suggested that the latter body is a product of hydrolysis of 

 a glucoside. 



Pending the introduction of more precise and convenient methods for 

 determining the distribution of oxydases in plant tissues our knowledge has 

 remained in this interesting but incomplete state. It is true that a number 

 of oxydase reagents is known but the method of their application, that of 

 adding the reagents to macerated tissues, cannot but lead to inconclusive 

 results. It is possible, however, as Clarke (1911) has demonstrated, to use 

 certain oxydase reagents for micro-chemical purposes and, as we show, 

 appropriate methods admit of both macroscopic and microscopic demon- 



