STUDIES IN PLANT RESPIRATION AND PHOTOSYNTHESIS. 



51 



again occurs the characteristic rise, which, however, is not main- 

 tained and the rate again falls, so that after about 60 hours the rate 

 of respiration is far below the initial rate, in spite of the fact that 

 the leaves have actually increased in carbohydrate-content. 



Table 28. 



Undoubtedly the carbohydrate supply alone does not determine 

 the rate of respiration, but there is necessary an accessory factor 

 which aids the successive chemical reactions constituting this process. 

 That amino-acids act in this stimulating manner is established by 



Table 29. — Rate of emission oj CO2 by 6 leaves of Helianthus annuus at 25°. 

 Petrioles in nitrogen-free nutrient solution containing 7 per cent d-glucose and 0.11 per cent 

 glycocoll. CO2 absorbed in Ba(0H)2 solution 0.1169 normal, 125 c. c. of which has the equivalent 

 of 0.3214 gram CO2. 



the experiments here described, and the point naturally suggests 

 itself that under normal conditions in the dark, when the carbohy- 

 drate-content decreases and the amino-acids increase, there is a 

 similar stimulating action which would tend to maintain a relatively 

 higher respiration rate. From such data as are available it appears 

 that the accumulation of amino-acids is a relatively slow process, and 



