NO. l6 CARBON DIOXIDE ASSIMILATION HOOVER ET AL. IQ 



accuracy in absolute terms the lack of accurate data as to leaf area 

 and chlorophyl concentration prevents one from attaching particular 

 significance to the slope of the linear variation. 



It is evident from this discussion that such an experiment does 

 not lend itself to an analysis of the transition range in terms of 

 chemical kinetics. The difficulty lies entirely in the nature of the 

 organism examined, so that further efforts in the direction of obtain- 

 ing more ideal conditions and further analysis of the energy distri- 

 bution, absorption characteristics, etc., would seem relatively fruitless. 

 It remains possible, however, to make a critical attack upon many 

 interesting problems of photosynthesis in cases where one is chiefly 

 concerned with the range in which one or the other of the variables 

 acts as a limiting factor. The method has the advantage of eliminating 

 many of the objectionable factors involved in experiments where 

 organisms are placed in abnormal growth conditions. 



CONCLUSIONS . 



A set of families of curves has been obtained showing assimilation 

 of carbon dioxide by young wheat plants over a wide range of 

 carbon dioxide concentrations and light intensities. Linear variation 

 of assimilation with carbon dioxide concentration in the presence of 

 excess light has been observed over a limited range. Linear variation 

 of carbon dioxide assimilation as a function of light intensity for 

 excess carbon dioxide concentration has also been observed over a 

 limited range. The transition range between the two regions of limit- 

 ing factors is more extensive in higher plants than in algae. This 

 may be expected from the lack of homogeneity of light intensity and 

 carbon dioxide concentration throughout the leaf. These experiments 

 indicate that a wide range of critical experiments upon photosynthesis 

 may be carried out with higher plants, using the technique developed, 

 so long as one is not particularly concerned with problems such as 

 constants of dissociation and others particularly relating to the transi- 

 tion range. 



