98 



STUDIES IN PLANT RESPIRATION AND PHOTOSYNTHESIS. 



simply a case of high photosynthesis supplying carbohydrates in 

 such large amounts that the leaf is at all times well supplied and thus 

 burns this sugar at a correspondingly high rate. 



The experiments on the relation of respiration and photosynthesis 

 are being extended, especially with a view of determining the temper- 

 ature coefficients under a variety of conditions. There is considerable 

 evidence for believing that the photosynthetic process is of a dual 



Figure 27. 

 Rates of photosynthesis and respira- 

 tion, on successive days, of a leaf of Hdi- 

 anthus annuus. The values above the 

 zero line indicate rates of photosynthesis, 

 those below, rates of respiration, ex- 

 pressed on the ordinates in mg. CO2 

 fixed, or emitted, per sq. cm. per hour. 

 Data and conditions as per table 57. 



UD 



n 



u 



nature or even more complex, involving the general principle of 

 coupled reactions. That one of these, or one group of these, reactions 

 is photochemical there seems to be little doubt. The nature of the 

 other reaction (Willstaetter's enzymatic reaction), or that associated 

 with the respiratory activity, is still very obscure. In what manner 

 these two sets of reactions complement each other or how they are 

 coupled is one of the most vital points of the photosynthesis problem. 

 Some speculations hereon were given in the introductory discussion 

 of this section. However, at this stage of development the only 

 method which promises any real advance is the experimental one. 

 In view of the importance and the insight which can be gained from 

 the interpretation of temperature coefficients on the basis of recent 

 physical-chemical investigations, an extension of these determinations 

 seems highly desirable and offers another means of analyzing the 

 phenomenon of photosynthesis. 



* 



