The Starch Content of Autumn Leaves. 147 



daceae, and Iridaceae. Combes * determined quantitatively 

 the insoluble carbohydrates and also sugars in the leaves of 

 plants collected after autumnal frosts. The leaves were picked 

 from the plant and not taken from the ground. The amount 

 of insoluble carbohydrates present in the green material so col- 

 lected by him was as follows; Rosa canina, 9.72%; Mahonia 

 aquilijoliiim, 2,38%; Sorbns latifolia, 11.99%. 



It is impossible to explain beyond question what the chem- 

 ical changes are that take place which prevent the leaves from 

 transporting their food materials to other parts of the plant be- 

 fore the leaves are dropped. Such an explanation must there- 

 fore necessarily be largely theoretical. 



It is a well known fact that before starch can be trans- 

 located it must be converted into a soluble carbohydrate. Such 

 a change is brought about by diastatic enzymes. Anything, 

 therefore which would destroy diastase or inhibit its activity 

 would also interfere with the translocation of starch. While 

 the writer has never followed out the chemical changes that 

 take place in maturing leaves in autumn, except the formation 

 of carbohydrates in Liquidamher styraciflua as mentioned, it 

 is possible that diastase is the first of the enzymes to suffer in 

 the destructive processes which take place in the cells. Woods f 

 showed that oxydizing enzymes under certain conditions re- 

 tarded or weakened the action of the translocation diastase. 

 He also calls attention to the fact that the coming on of cool 

 weather in autumn and the approach of maturity in the leaf 

 stimulate the production of oxidizing ferments. J It is possible, 

 therefore, that diastase, either as the result of the inhibitory 

 action of the oxidizing enzymes or its complete destruction by 

 some other means in the leaves of the plants here studied, has 

 lost its power of converting starch into sugar before the chloro- 

 phyll in the leaves ceases carbon assimilation. Under such 

 conditions the chlorophyll might continue to manufacture starch 

 which because of the inactivity of the translocation diastase, 

 must necessarily remain in the leaves of the plant, and if continued 

 for a number of days might accumulate in considerable amount. 



•1. c. 



tWoods, A. F. Inhibitine action of Oxidase upon Diastase, Science, N.S., 11: 17. 1900. 



♦Woods, A. F. Autumnal Coloration of Foliage. Enclyclopedia of Horticulture. 



