STUDIES IN PLANT RESPIRATION AND PHOTOSYNTHESIS. 



93 



stands out and has been observed repeatedly, that under the con- 

 ditions of the experiment, the rate of photosynthesis of a leaf, the 

 store of carbohydrates of which has been greatly reduced, is initially 

 low and rises with continued exposure to light. Thereby the respi- 



Table 55. — Rates of respiration and photosynthesis of leaves of Helianthus annuus at 34°. 



Taken after plant had been exposed to sunlight and after increasing periods of darkness. 

 In atmospheric air, light intensity 7.140 lux. 



fFirst leaf, 106.55 sq. cm.] 



ration rates also show an increased rate and subsequent periods of 

 photosynthesis exhibit correspondingly higher rates. The results 

 of this experiment are shown graphically in figure 24. 



2 The following experiment was carried out in a different manner. 

 A mature leaf was cut from a large, healthy sunflower plant which 



