STUDIES IN PLANT RESPIRATION AND PHOTOSYNTHESIS. 



45 



In order to compare the respiratory activity of the two sets of 

 leaves, those with and those without glycocoll in the nutrient 

 solution, the determinations of carbon dioxid are summarized in 

 table 21. 



From the foregoing it is evident that the leaves which had been 

 fed glycocoll respired more actively than those without the amino- 

 acid. On the basis of fresh material, the former produced 22.43 



Table 20. 



per cent more carbon dioxid than the latter, and on the basis of 

 dry material the respective difference was 15.09 per cent in favor 

 of the leaves given glycocoll. It is also evident that the leaves which 

 had had glycocoll showed a much greater reduction in the amount 

 of carbohydrates; the slight difference in the length of time the two 

 experiments ran would have but slight effect on these results. It 



Table 21. 



might be argued that the leaves given glycocoll had an original 

 higher content of carbohydrates and that this might account for 

 the greater respiratory activity. However, it has been our experi- 

 ence in a great many cases that within certain upper and lower 

 limits the initial carbohydrate-content does not influence the rate 

 of respiration under controlled conditions of temperature and water- 

 supply. Finally, it is also noticeable that the leaves given glycocoll 

 have a higher amino-acid content at the end of the experiment. 



3. d-Glucose. 



From the foregoing experiments the simple facts become evident 

 that when excised leaves are kept in the dark at 25° the amino- 

 acid content rises, and that when the leaves are given glycocoll 



