52 



STUDIES IN PLANT RESPIRATION AND PHOTOSYNTHESIS. 



it seems highly probable that the rise in the respiration rate observed 

 after 30 to 40 hours represents the time when the amino-acids have 

 accumulated sufficientlj^ and their influence on the rate of respiration 

 becomes noticeable. The experiments on this point will be taken 

 up later. 



40 50 60 70 



FlGtTBB 13. 



Rate of respiration of 6 leaves of Helianthus anmms at 25°; petioles in nitrogen-free 

 nutrient solution containing 7 per cent d-glucose and 0.11 per cent glycocoll. Values 

 taken from table 29. The ordinate represents mg. CO2 per hour per gram dry material, 

 the abscissa the time in hours. 



Turning now to the experiments in which amino-acids were fed 

 the leaves, it should be noted that the conditions here were precisely 

 the same as in the foregoing experiments, with the exception that 

 the nutrient solution contained, besides the inorganic salts and the 

 specific sugar, a definite amount of amino-acid. In tables 23, 25, 



Table 30. 



and 27 were presented the results of respiration determinations of 

 leaves which had been given d-glucose. In the following experi- 

 ment with Helianthus leaves 0.11 per cent of glycocoll was added to 



