STUDIES IN PLANT RESPIRATION AND PHOTOSYNTHESIS. 



53 



the nutrient solution. The analytical data show that during the 

 course of the experiment the leaves gained both in amino-acids and 

 in carbohydrate-content. 



Table 31. — Rate of emission of CO2 by 6 leaves of Helianthus annuus at 25°. 

 Petioles in nitrogen-free nutrient solution containing 7 per cent d-glucose and 0.16 per cent 

 asparagine. CO2 absorbed in Ba(0H)2 solution 0.11835 normal, 125 c. c. of which has the COj 

 equivalent of 0.3254 gram CO2. 



From the determinations of the rates of CO2 emission, given in 

 table 29 and figure 13, it is apparent that when the leaves are given 

 both d-glucose and glycocoU the rate of respiration rises at once 

 and, with slight irregularities, maintains this increased rate for at 

 least 74 hours. The stimulating action of glycocoll becomes evident 

 when the graph of the experiment is compared with the three pre- 

 ceding ones. This is especially apparent during the first 35 hours, 

 that is, before the effect of the amino-acids accumulating in the 

 leaves becomes noticeable. 



Table 32. 



That other amino-acids have a similar effect is shown by the fol- 

 lowing experiment with asparagine and Helianthus leaves. All con- 

 ditions were kept precisely the same and the nutrient solution 

 contained 0.16 per cent of asparagine. The analytical data in table 30 



