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VIII. 



OXYDASES AND THEIR INHIBITORS IN PLANT TISSUES. 



Pakt II. THE FLOWERS AND LEAVES OF IRIS. 



By W. R. 0. ATKINS, Sc.B., A.I.O., 

 Assistaut to the Professor of Botany, Trinity College, Dublin. 



[Read November 25, 1913. Published January 16, 1914.] 



In the first paper by the writer under the above general title (1), it was 

 shown that, in the leaf of Iris germanica, there exists a substance which 

 prevents the detection of oxydases by the direct application of guaiacum 

 solution and hydrogen peroxide. This inhibitor is eSective both in 

 leaf-sections and in sap from leaves pounded in a mortar. Furthermore 

 a blue solution of oxidized guaiacum is immediately decolorized by the 

 reducing action of this substance. Dialysis of the sap pressed from the 

 leaves results in the disappearance of the reducing agent, leaving behind 

 the oxydase or pero.xydase. Active preparations of the enzymes may also 

 be obtained by precipitating them with strong alcohol, as the reducing 

 agent remains in solution. 



The objects of the present research are (a) to determine qualitatively the 

 effect of light and darkness upon the oxydases and reducing substances of 

 Iris leaves; and (b) to study the relationship of oxydases and reducing 

 agents to the production of colour in the flower of Iris, by means of the 

 reagents, found suitable by Keeble and Armstrong (4, 6, 6) in their 

 fascinating work on otlier types of flowers. 



The Oxydase Reagents. 

 To detect oxydases in cut sections of Iris sp. a very dilute aqueous 

 alcoholic solution of guaiacum resin was employed. This was followed by 

 hydrogen peroxide also dilute and neutral; with both sections and perianth 

 leaves dilute solutions of benzidine and a-naphthol in aqueous alcohol were 

 used, with subsequent addition of the peroxide. The reaction is blue with 

 guaiacum, blue to brown with benzidine, and a lilac purple with a-naphthol. 

 The use of the two latter reagents in this connection has been advocated 

 by Clarke (2), and by Keeble and Armstrong (4), and has been found 



SCIENT. PKOC. E.D.S., VOL. XIV., NO. VIII. ^ A 



