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VII. 



\ 



ON THE INHIBITION OF INVERTASE IN THE SAP OF 

 GALANTHUS NIVALIS. 



MAR'S 1921 



>v 



By T. G. MASON, M.A., Sc.E. 



Read Febkuary 24. Published April 12, 1920. 



In view of the widespread occurrence of inverfcase in the leaves of plants (8), 

 it seemed probable that an approximate estimate of the svicrose-content of the 

 sap could be obtained by observing the increase in depression of the freezing- 

 point after storage at a suitable temperature. 



Asa Iper cent, solution of sucrose has a depression of 0'054° C, whereas 

 after its hydrolysis to invert sugar it has approximately double this de- 

 pression, a method is provided of recording the amount of sucrose inverted (7). 



The experiments were carried out on the Snowdrop {Galanthus nivalis), 

 and, as starch and inulin are absent from its leaves (10), the difficulties which 

 might be introduced by the production from these sources of maltose, dextrose, 

 and levulose need not be considered. 



In the earlier experiments made on this matter it was found that other 

 factors, which tended to limit the activity of the enzyme, were present; 

 consequently it was considered that an investigation of their nature might 

 prove of interest. 



The freezing-point determinations were made by means of Dixon's 

 thermo-electric method (4 and 5). 



The saps for the freezing-point determinations shown in Table I were 

 pressed from tissues rendered permeable by exposure to intense cold. To do 

 this the leaves were rolled and packed in test-tubes, which after sealing were 

 immersed for two hours in a freezing mixture of salt and ice ("-16° C). 



The white bases of the leaves were rejected, and the sap, as pressed from 

 the leaves, was collected in test-tubes iitted with an ice-jacket to prevent 

 inversion. 



Sap was also pressed from leaves which had not received any treatment. 



SCIENT. PROC. K.D.S., VOL. XVI, NO. VII. L 



