960 CONCENTKATIOX FACTORS CHAP. 27 



tion of urethan causes an increase in F (of. fig. 28.50B), so that the intensity 

 of fluorescence finally becomes about the same with and without reductant. 



It is noteworthy that in the completely narcotized state {e. g., with 3% 

 ethylurethan, when the gas exchange is completely inhibited; cf. fig. 27.19) 

 the characteristic curvature of the fluorescence curves of bacteria disap- 

 pears (fig. 28.50B). 



These results can be explained by the assumption that lU'ethan reacts 

 directly with the primary photochemical complex XBchl-HZ, and that 

 the product of this interaction is characterized by a yield of fluorescence 

 about halfway between those of the forms X-Bchl-HZ and X-Bchl-Z. 



Oxygen. In chapter 13 (Vol. I, page 328) we described the inhibiting 

 effect of excess oxygen on photosynthesis. The light curves of photosyn- 

 thesis and fluorescence in the presence and absence of oxygen will be dis- 

 cussed in chapter 28. The only systematic measurements with varying 

 oxygen pressures permitting the plotting of an "oxygen curve," P = /[O2], 

 were made by Warburg (1920); the results were reproduced in figure 32. 

 This figure indicated the steepest rate decline between and 20% oxygen; 

 it was mentioned that this was contradicted by Wassink and co-workers 

 (1938), who found no difference between the rates at and 20% oxygen, 

 but a considerable drop from 20 to 100% oxygen. 



Bibliography to Chapter 27 



Concentration Factors 



A. Experimental Carbon Dioxide Curves 



1804 de Saussure, T., Recherches chimiques sur la v^gHaiion. Paris, 1804. 



1865 Boussaingault, J. B., Covipt. rend., 60, 872. 



1873 Bohm, J., Sitzber. Akad. Wiss. Wien, Math.-naturw. Klasse. AM. I, 68, 171. 



1881 Stefan, M. J., ibid., Abt. II, 83, 943. 



1885 Kreusler, U., Landw. Jahrb., 14, 913. 



1887 Kreusler, U., ibid., 16, 711. 



1895 Blackman, F. F., Trans. Roy. Soc. London, B186, 503. 



1896 Ewart, A. J., /. Linnean Soc, London, 31, 364. 



1900 Brown, H. T., and Escombe, F., Trans. Roy. Soc. London, B193, 223. 



1902 Brown, H. T., and Escombe, F., Proc. Roy. Soc. London, B70, 397. 

 Chapin, P., Flora, 91, 348. 



1903 Treboux, 0., ibid., 92, 49. 



Pantanelli, E., Jahrb. wiss. Botan., 39, 167. 



1904 Demoussy, E., Cmipt. rend., 139, 883. 



1907 Xathansohn, A., Ber. sacks. Ges. Wiss., Math.-naturw. Klassc, 59, 211. 



1910 Heiiaer, 0., Flora, 100, 451. 



Nathansohn, A., Der Stoffwechsel der Pjlanze. Quelle & Meyer, Leipzig. 



1911 Aiigelstein, U., Beitr. Biol. Pflanz., 10, 87. 



Blackman, F. F., and Smith, A. M., Proc. Roy. Soc. London, B83, 389. 



