1 8 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



(a) Action of Oxidase. 



If a guaiacum solution is treated with an oxidising agent 

 such as potassium permanganate (KMnOj) or manganese 

 dioxide (MnOo), it is oxidised and assumes a deep blue colour. 

 Research has shown that many plant extracts are capable of 

 bringing about this reaction, and it has been ascertained that 

 this oxidising power of plant extracts is due to an enzyme or 

 enzymes which have been grouped under the name of 

 Oxidases. 



When using guaiacum resin, to obtain the blue colour 

 indicative of oxidation, the addition of hydrogen peroxide is 

 often necessary, in which case the enzyme is called Peroxidase. 

 It has been inferred from this that where the blue colour appears 

 without the addition of hydrogen peroxide, another enzyme 

 is present, which fulfils the function of hydrogen peroxide, and 

 this enayme has been called Oxygenase. Oxidase, therefore, 

 is taken as a combination of Oxygenase and Peroxidase, but 

 since Oxygenase is thought to be very unstable and destroyed 

 in the presence of air, the reaction for Oxidase is often difficult 

 to obtain, the addition of a peroxide being necessary. Some 

 believe that Oxygenase is hydrogen peroxide. The Peroxidase 

 acts on the Oxygenase, liberating oxygen, which oxidises the 

 guaiacum resin. 



{b) Oxidase Secretion by Roots and Mycorhiza. 



(i) The secretion of Oxidases and Peroxidases by the roots 

 of Higher Plants has been demonstrated by various investi- 

 gators. Borkowski experimented on various species of plant 

 with -05 and '01 % solutions of ammonium ferrosulphate, and 

 showed that roots possess considerable powers of oxidation, 

 this power being localised in the region of the root-hairs and 

 root-tip. The oxidation was also found to take place in the 

 central cylinder, especially in the wood bundles. Shreiner 

 and Reid ^ by using various reagents, such as guaiacum resin 

 and aloin, obtained similar results. 



(2) Members of the Coniferae possessing root-hairs have 

 been found to give similar results when tested with guaiacum 

 resin tincture. Oxidases and Peroxidases are only demon- 

 strable m the root-hairs. The blue colour appears in the 



^ Bot. Gaz., 1909, 47. 



