1 68 PHYSIOLOGY OF NUTRITION 



In the half of the endosperm nearest to the embryo 9 . 7970 



In the half of the endosperm farthest from the embryo 3 ■ 5310 



In the roots o . 0681 



In the leaves o . 0456 



In the scutellum o . 5469 



Total 13 • 9886 



It thus appears that, in such seedlings, diastase is most plentiful in the 

 endosperm. 



Diastase is less easily demonstrated in leaves of mature plants than in 

 germinating seeds. Extracts of fresh leaves contain almost no diastase, since 

 the enzyme diffuses hardly at all through cell walls. Brown and Morris 1 

 recommended the following method for obtaining it from leaves. The leaves 

 are dried at 40 to 5o°C, after which they are ground to a fine powder, which is 

 allowed to act upon starch in water. Different leaves have different diastatid 

 powers, as may be seen from the table given below, in which the relative effi- 

 ciencies of leaf powders from five different plants are presented. 



Pisum sativum (pea) 240 . 30 



Lathyrus odoratus 100 .37 



Helianthus anmius (sunflower) 3-97 



Syringa vulgaris (lilac) 2.52 



Hydrocharis morsus-rana 0.26 



The greater is the tannin content of leaves, the weaker is the diastatic power. 

 Detailed researches have shown that diastase consists of a mixture of at least 

 two different enzymes, amylase and maltase. Amylase effects the transforma- 

 tion of starch to maltose, which in turn is transformed into glucose through the 

 action of maltase. 



Starch is replaced by inulin in the tubers of some plants, such as Inula, 

 Helianthus, Dahlia. The cleavage of inulin takes place through the agency of 

 a specific enzyme, inulase. For the isolation of inulase a glycerine extract is 

 prepared from dried sprouting tubers and the extract is dialyzed. The solution 

 of inulase thus obtained produces hydrolytic cleavage of inulin. 



Saccharase (invertase) hydrolyzes saccharose and is especially abundant in 

 yeast. It is concentrated in the following way. Yeast that has been dried 

 at 40°C. is heated for six hours at ioo° and is then placed in water and left undis- 

 turbed for twelve hours at 40 . The preparation is then filtered and alcohol is 

 added to the filtrate. A precipitate is thus formed, which is purified by being 

 repeatedly dissolved in water and reprecipitated with alcohol. One part of the 

 dry precipitate is capable of inverting 700 parts of saccharose when in solution. 



Emulsin is found in sweet almonds. It splits the glucoside amygdalin 

 into glucose, hydrocyanic acid and benzaldehyde." 



1 Brown and Morris, 1893. [See note, 1, p. 28.] 



» The complete hydrolysis is represented by the equation : 



Hydrocyanic 

 Amygdalin Glucose acid Benzaldehyde 



CmHjtNOh + 2H 2 = C 6 H 12 6 + HCN + C 6 H 5 CHO.— Ed. 



