Mason — Inhihition of Invertase in the Sap of Galanthus nivalis. 89 



toluened sap + sucrose solution might, by lowering the surface-tension, free 

 the enzyme if present from any adsorbent colloid. 



No increase in hydrolysis could, however, be detected in the samples 

 treated with saponin. 



This need not negative the adsorption view of the inhibition, as not only 

 is there evidence that a saponin is normally present in the sap, but the 

 adsorption might well be specific. 



The absence of a precipitation of colloids on storage from the toluened 

 samples suggests that the precipitation may have taken place in the cell- 

 vacuoles during the exposure of the leaves to toluene vapour, and that possibly 

 the enzyme was removed with the colloids, and therefore was not extracted 

 with the sap. 



1015 



0-548 



30 40 50 

 time: in hours 



Fig. 3. 



As the presence of inhibiting factors seemed to be a possible explanation 

 of the observed depressions of the freezing-point, the saps (from the frozen 

 and untreated leaves) were placed aside in the thermostat for a further forty- 

 eight hours in order to see whether or not by then adding invertase the 

 hydrolysis of sucrose was complete. 



On withdrawing these saps (after 120 hours' incubation at 29°), they were 

 boiled for one minute, as described in the second experiment. 



To 5 gm. of the boiled and filtered saps was added 0-33 gm. of invertase 

 solution, prepared by Davis' method (3). Before the addition of the invertase 

 the saps were cooled to - 2° with a view to checking inversion till the freezing- 

 points had been determined. When the observations were completed, the 

 samples were stored for approximately twenty-four hours at 29°. The results 

 are shown in Table VI . 



