74 CARBOHYDRATES AND THEIR [CH. 



The diastatic activity of leaves appears to vary largely in different 

 genera and species. The subject has been investigated (Brown and 

 Morris, 5) and a list of their relative activities has been drawn up as 

 follows. 



[The numbers represent the amount of maltose, expressed in grams, which 10 

 gms. of air-dried leaf will produce from soluble-starch (starch treated with dilute 

 hydrochloric acid) by hydrolysis in 48 hrs. at 30 C.] 



Pisum sativum 240*30 Heliaiithus animus 3*94 



Phaseolus multiflorus 110-49 H. tuberosus 3*78 



Lathyrus odoratus 100*37 Funkia sinensis 5*91 



L. pratensis 34-79 Allium Cepa 3*76 



Trifoliuui pratense 89*66 Hemerocallis fulva 2 '07 



T. ochroleucum 56*21 Populus sp 379 



Viciasativa 79*55 Syringa vulgaris 2*53 



V. hirsuta 53*23 Cotyledon Umbilicus 4*61 



Lotus corriiculatus 19*48 Humulus Lupulus 2*01-9*60 



Lupinus sp 3*51 Hymenophyllum demissum . . . 4*20 



Grass with Clover 27*92 Hydrocharis Morsus-ranae ... 0*267 



Tropaeolum majus 3*68-9*64 



From the above table it is seen that the leaves of genera of the 

 Leguminosae are apparently very rich in diastase. Whether this is so, 

 or whether in other plants the diastatic activity is inhibited by other 

 substances, has not yet been ascertained. As mentioned above, tannins 

 inhibit the action of diastase, and hence leaves rich in tannin, e.g. Hop 

 (Humulus), cannot be expected to yield good results. 



The tissues of germinating barley (Hordeum vulgare) also contain 

 large quantities of diastase, and this material can be used to demon- 

 strate the solubility, isolation and activity of the enzyme. 



The action on starch of diastase from the leaf of the Common Pea 

 (Pisum sativum) and from germinating barley grains has already been 

 demonstrated [see Expt. 57 (a) and (b)] in connexion with dextrin. The 

 following experiments have special reference to the enzyme. 



Expt. 78. To demonstrate the activity of diastase from germinating barley. Grind 

 2-3 gms. of barley grains in a coffee-mill. Boil the product with 100 c.c. of water 

 and filter, first through fine muslin if necessary, then through "filter-paper. A starch 

 " solution " will be obtained. 



Pound up 2-3 gms. of germinated barley grains in a mortar and extract the mass 

 with 50 c.c. of water. Filter, and take two equal portions in two test-tubes. Boil one 

 tube. To both tubes add an equal quantity of the starch solution prepared above. 

 Place the tubes in a beaker of water at 38-40 C. From time to time withdraw a 

 drop from each tube with a pipette and test with iodine solution on a white tile. The 

 starch in the unboiled tube will gradually give the dextrin reactions (see p. 57); that 

 in the boiled tube will remain unchanged. 



