STUDIES IN PLANT RESPIRATION AND PHOTOSYNTHESIS. 



55 



in the dark for 76 hours. The rate of respiration as shown in table 33 

 and figure 14 is also correspondingly low and the rise in the rate 

 comes quite late. 



Table 33. — Rate of emission of CO2 by 6 leaves of Helianthtis annuus at 25°. 

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

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

 lent of 0.3254 gram CO2. 



4. Sucrose. 



Some attention was also given to the influence of sugars other 

 than d-glucose. Thus the rate of respiration was determined of 

 leaves which were given sucrose as well as a mixture of this sugar 

 and an amino-acid. In these experiments the conditions as to 

 temperature, etc., were the same as in the preceding determinations. 



Table 34 gives the analytical data of the leaves in the initial 

 condition and after having stood in the dark with the petioles in a 

 nitrogen-free nutrient solution containing 7 per cent of sucrose. 



Table 34. 



The rates of respiration of this experiment are given in table 35 

 and figure 15. It will be noted that although there is a slight increase 

 in both the amino-acid and carbohydrate-content, the leaves do 



