24 PLANT RESPIRATION 



increases considerably after a short stay in pure water. « Possi- 

 bly the temporary withdrawal of oxygen is here to be considered 

 as the cause. Later, attention will be called to the striking 

 increase in respiration after temporary anaerobiosis, the 

 explanation of which agrees with the modern theories of 

 respiration. According to the data of Kostychev, a slightly 

 alkaline reaction of the surrounding solution has a stimulating 

 influence on the respiratory process.^ This agrees with the 

 consideration that the enzymatic, biochemical, oxidation proc- 

 esses require a slightly alkaline reaction.'' 



The Influence of Yeast Extracts and of Sugar Solutions 

 Fermented by Yeast, on the Respiration of Plants. — According 

 to the statements of Kostychev and his coworkers- the oxygen 

 respiration of plants is very strikingly increased by yeast 

 extracts and particularly by sugar solutions fermented by yeast. 

 This condition will engage our attention later in connection 

 with the discussion of the chemical nature of normal plant 

 respiration. Since alcoholic fermentation may be regarded as 

 one of the first steps in the physiological oxidation of sugar, a 

 violent oxidation of the oxidisable intermediate products of 

 sugar respiration, formed by yeast, could occur in the above 

 cases. ^ On the other hand, it is also plausible that the vitamines 



> Kostytschew, S. und A. Scheloumow. Jahrb. f. wiss. Bot. 50: 157. iQn; '/• also 

 Loeb, J. und H. Wasteneys. Biochem. Z. 37: 410. 191 1; Jour. Biol. Chem. 14: 335. 459. 

 469, 517. 1913; 21: 153. 1915. [For the influence of hydrogen ion concentration on 

 respiration see Gustafson, F. G. J. Gen. Physiol. 2: 617-626. 1919-20, and Bode, H. R. 

 Jahrb. f. wiss. Bot. 65: 352-387. 1926. The latter deals only with Spirogyra and chiefly 

 on the acid side of neutrality.] 



2 Kostytschew, S. Biochem. Z. 15: 164. 1908; 23: 137. 1909; Physiol.-chem. Unter- 

 such. iiber Pflanzenatmung. 1910. Russian; Kostytschew, S. und Scheloumow. loc. 

 cit.: Ber. d. bot. Ges. 31: 422. 1913; Kostytschew, S., Brilliant, W. und A. Scheloumow. 

 Ibid. 31 : 432. 1913. 



2 Yeast effects a vigorous alcoholic fermentation but an insignificant oxidation. With 

 restricted access to oxygen it is also unable to oxidise alone all the fermentation products 

 which are formed. 



9 Water can hardly be termed "chemically indifferent" for it is very generally 

 accepted that its presence is essential for all, or nearly all, chemical (and hence 

 physiological) reactions. — Ed. 



"■ It is difficult to reconcile this suggestion with the increasing evidence that the 

 reaction of those parts of the protoplasm which may be tested is found to be on 

 the acid rather than the alkaline side of neutrality (c/. Crozier,W. J. Proc. Soc. 

 Exptl. Biol. Med. 21 : 58. 1923). On the other hand the influence of an alka- 

 line reaction may be regarded as more favorable to the catalytic action of iron 

 (Warburg, O. Science 6i : 575-582. 1925; Meyerhof und Matsuoka. Biochem. 

 Z. 150: i-i r. 1924) or to the third ionization of phosphates which are reported 

 to increase the rate of respiration (see editorial note k, page 126). — Ed. 



