318 



The Formation of the Anthocyan Pigments of Plants. 

 Pai't V. — The Chromogens of White Flowers* 



By W. Neilson Jones, M.A., Lecturer in Botany, University College, 



Beading. 



(Communicated by W. Bateson, F.B.S. Beceived February 4, — Bead 

 February 27, 1913.) 



The series of communications of which the present paper forms a part 

 '(Part V) deals with the biochemistry and genetics of pigmentation in plants. 

 Parts I and III of the series describe the rdle of oxydases in the formation 

 of the anthocyan pigments of flowers ; Part IV gives an account of the 

 chromogens which constitute the colourless antecedents of these pigments ; 

 and the present paper has for its object the investigation of the chromogens 

 in white flowers. 



The subject is of interest from the point of view both of biochemistry 

 and genetics ; for, as has been discovered by Mendelian research, the white 

 flowers which occur so commonly in cultivated and wild plants belong to 

 more than one category. 



The types of white flowers recognised hitherto are known respectively as 

 dominant and recessive whites. As shown by Keeble and Armstrong, both 

 dominant and recessive white flowers contain oxydase (or peroxydase). In 

 the former the oxydase is inactive owing to the presence of an inhibitor ; in 

 the latter it is active. 



Inhibition of oxydase suffices to account for the absence of colour from 

 dominant white flowers. In order to account for the absence of colour 

 from recessive whites it is assumed that some part of the colour-forming 

 mechanism — for example, the chromogen — is lacking from the flowers. It is, 

 however, possible that lack of colour may be in some cases the consequence 

 not of absence of an essential constituent of the colour-producing mechanism, 

 but of the failure of these constituents — all of which are present in the 

 flower — to come together and interact with one another. 



The results of experiments about to be described show that both kinds of 

 recessive white flowers exist. 



As the result of treating the white flowers of Lychnis coronaria var. alba 

 with alcohol (15-80 per cent.), chloroform, ether, or carbon disulphide, a 

 brown pigment develops. 



* Parts I and II, Keeble and Armstrong, 'Eoy. Soc. Proc.,' 1912, B, vol. 85, pp. 214 

 and 460; Part III, Keeble and Armstrong, 'Journal of Genetics,' November, 1912; 

 Part IV, Keeble, Armstrong, and Jones, 'Bx>y. Soc. Proc.,' 1913. 



