40 



STUDIES IN PLANT EESPIRATION AND PHOTOSYNTHESIS. 



similar Helianthus plants of the same age and size, growing in large 

 pots, were used; the one was analyzed at once, the other after being 

 in the dark at 20° for 96 hours. 



Table 13. — Analyses of Helianthus annuus plants, leaves, stems, and roots separately after 

 exposure to light for 5 hours and after being in the dark for 96 hours. 



The analyses in table 13 show a general decrease in the carbo- 

 hydrate-content of the plant kept in the dark. Here also the leaves 

 of the plant kept in the dark show an increase in amino-acids. The 

 stems and roots, however, show a very slight decrease in amino 

 compounds. 



The experiments of Schulze and Castoro^ on the accumulation of 

 amino-acids have already been mentioned. In this work the seedlings 

 were kept in the dark for 2 weeks and the amino-acid content in 

 these plants was very much higher than in the ones exposed to the 



Table 14. — Amino nitrogen in beans (Canada 

 Wonder) sprouted on sawdust. 



light. During this length of time the seedlings were capable of 

 developing well-formed chlorophyllous leaves. We carried out 

 comparative experiments in which periodic analyses were made on 

 germinating seeds, in the light and in the dark, for a shorter time, 

 the seedlings having still available some stored proteinaceous matter. 

 In these experiments no differences of consequence were observable 

 between the seedlings grown in the dark and those grown in the light. 



1 Schulze, E., and N. Castobo. Zeitschr. physiol. chem., 38, 244 (1903); 49, 72 (1906). 



