270 



Plant Physiology 



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and finally maltose which is subsequently converted 



by the enzyme glucase into glucose. 



The diastases are widespread, and two forms are dis- 

 tinguished accord- 

 ing to the type of 

 corrosion of the 

 starch grain. 

 Diastase of trans- 

 location occurs es- 

 pecially in the 

 chlorenchyma of 

 leaves, and it cor- 

 rodes the grain 

 almost evenly.' 



FIG. 68. Corrosion of starch grains by dias- Diastase of S6Cre- 

 tase of secretion. [After Strasburger.] . ,. 



tion, corroding the 



grain irregularly (Fig. 68), is that which occurs in storage 

 organs generally, but especially in seeds. Apparently a 

 third form, takadiastase, is the product of Aspergillus 

 Oryzce in its action upon wheat or rice starch. Allied to 

 diastase is inulase, converting inulin into fructose. 



Cytase is a ferment often associated with diastase, as 

 in the endosperm. It may be important in the dissolution 

 of a certain " shell " of the starch grain. It is, however, 

 best known from its action on the reserve cellulose, con- 

 verting this into hexose sugars. It is probable that 

 several enzymes are required in the decomposition of other 

 celluloses, about which very little is known. 



It has been indicated incidentally that the disaccharids 

 sucrose and maltose are hydrolyzed and yield hexoses by 

 invertase and glucase respectively. These enzymes are 



