OXYGEN RESPIRATION 1 9 



In pure oxygen plants respire more \'igorously but are soon 

 killed by it/ 



The question has also been raised whether a deficiency of 

 oxygen does not exist naturally in the interior of large plant 

 parts because of the insufficient aeration. Older workers- 

 expressed their opinion that the systematic arrangement of 

 plant organs precludes a deficiency, yet it subsequently appeared 

 that this question is complicated. It was shown that living 

 wood parenchyma cells, ^ roots,'* and germinating seeds with 

 compact, swollen coats'^ have an oxygen deficiency under 

 natural conditions. In large fruits the composition of the gas 

 mixture in the internal hollow spaces is not the same as that of 

 the atmospheric air. An analysis of the gas contained in the 

 hollow of a large pumpkin gave the following result: COo = 

 2.52%, Oo — 18.29%.^ In this case of course there can be no 

 question of an oxygen deficiency. ~ The assumption is not 

 precluded that some plants store quite large amounts of loosely- 

 bound oxygen. This oxygen is set free in an active condition 

 when needed and is used in the oxidation of the respiratory 

 material. 



The Influence of COo-concentration on Respiration. — Green 

 plants can tolerate high concentrations of CO2 in the light 

 without injury. However, according to de Saussure, a 4% 

 content of carbon dioxide injures plants. With a high content 

 of CO2 seed germination is entirely checked,^ but is again 

 started upon restoration of the normal composition of the sur- 



1 Borodin, J. Bot. Zeitg. 39: 127. 1881; Deherain et Landrin. Compt. rend. 78: 

 1488. 1874. 



2 Pfeffer, W. Abh. Math-physik. Klasse Sachs. Ges. d. Wiss. 15: 449. 1889; Celakow- 

 ski. F'ora. 76: 194. 1892. 



3 Devaux. Compt. rend. 128: 1346. 1899; Mem. de la soc. sciences phys. et natur. 

 Bordeaux. June 15, 1899. 



* Stoklasa, J. und A. Ernest. Jahrb. f. wiss. Bot. 46: 55. 1909. 



^ Kostytschew, S. Biochem. Z. 15: 164. 1908; Physiol. -chem. Untersuch. uber die 

 Pflanzenatmung. 1910. Russian. 



6 Devaux, H. Ann. sci. nat. bot. (VII) 14: 297. 1891; Rev. g6n. de bot. 3: 49- 1891. 

 [Langdon and Gailey (Langdon. Jour. Amer. Chem. Soc. 39: 149. 1917; Langdon and 

 Gailey. Bot. Gaz. 70: 230. 1920) report carbon monoxide as a respiratory product in the 

 hollow pneumatocysts of Nereocystis Luetkeana. The bladders contain nitrogen, oxygen 

 (is to 25%), carbon monoxide (i to 12%) and no carbon dioxide.] 



' Gerber. (Ann. sci. nat. bot. (VIII) 4:1. 1896) attempted to prove that a considerable 

 oxygen deficiency often prevails in the interior of fleshy fruits on account of which alcoholic 

 fermentation is introduced as a normal process in fruits. 



s Bernard, CI. Lemons sur les effets des subst. toxiques. 1883. P. 200. 



