54 



STUDIES IN PLANT RESPIRATION AND PHOTOSYNTHESIS. 



show that while the initial carbohydrate-content was not quite 

 maintained at the end of the experiment, there was a decided gain 

 in amino-acids. 



The determinations of the rates of carbon-dioxid emission are 

 given in table 31 and figure 14. A noteworthy feature of these 

 results is the rather rapid initial drop in the respiration rate before 

 the subsequent rise. This is probably due to the time required for 

 the asparagine to pass through the petiole and penetrate into the 

 cells. GlycocoU, on the other hand, has notable penetrating 

 qualities, and the effect of this amino-acid becomes noticeable very 

 quickly in the respiration-rate. 



20 30 40 



Figure 14. 

 Broken line indicates rate of respiration of 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; from table 31. The solid line indicates the rate of respiration of leaves 

 of Helianthus annuus at 25°, petioles in nitrogen-free nutrient solution containing 7 per 

 cent d-glucose and 0.11 per cent of alanine; from table 33. The ordinate represents 

 mg. CO2 emitted per hour per gram dry material, the abscissa the time in hours. 



Alanine seems to be taken up very slowly. The same conditions 

 were maintained as in the preceding experiments and pure alanine 

 was given as the amino-acid. The analytical data in table 32 show 

 a relatively slight increase in amino-acids after the leaves had been 



