STUDIES IN PLANT RESPIRATION AND PHOTOSYNTHESIS. 



65 



content of the leaves. Nevertheless, the respiration rates at the 

 end of the experiment show a remarkable increase over the initial 

 rates, although the latter were relatively not low. There is here 

 the same phenomenon, exhibited by d-glucose in figure 11, of an 



Table 47. — Rate of emission of CO2 by 8 leaves of Helianthus annum at 25°. 

 Petioles in nitrogan-free nutrient solution containing 7 per cent mannose. CO 2 absorbed 

 in Ba(0H)2 solution 0.12153 normal, 125 c. c. of which has the CO2 equivalent of 0.3343 g. CO2. 



increased respiration rate with decreased total sugar-content and 

 increased amino-acids. The sugar-content alone is no index of the 

 rate at which the leaves utilize this material. Moreover, under the 

 conditions of the experiment, where sugar is being constantly sup- 



Table 48. 



plied, it is quite conceivable that this is oxidized as rapidly as it is 

 taken up. This state of affairs must, of course, also frequently 

 exist under natural conditions. But the increased rate of respiration 

 at the end of the experiment can not be due to a greater supply of 

 sugar, but to the cooperation of some other factor which increases 

 its activity with time. The increase in amino-acids under the 

 circumstances is more than a coincidence and plays an important 



