OXYGEN RESPIRATION 



25 



and similar stimulating substances in the yeast extracts induce 

 a powerful stimulation of respiration. 



In any case it is important that the increase in rate of respira- 

 tion under the influence of fermented sugar solutions is entirely 

 unique. Such an increase is not even approximately reached 

 by the provision of nutrients or even by the action of poisons. 

 The above table of Morkowin shows that the rate of respiration 

 of plants stimulated by poisons reaches at the most 266% of 

 the normal rate (the quinine effect). From fermented solu- 

 tions there results C02-productions which exceed 400-600% 

 of the normal rate for the material used. In examining the 

 following table it is to be taken into consideration that the 

 respiratory intensity of control portions (in 5% sugar solution) 

 amounts to 150% of the normal of the wheat embryos (without 

 sugar). The table is an extract taken from S. Kostychev and 

 A. Scheloumow. 



This table shows that fermented sugar solutions always effect 

 a larger increase of respiratory energy than sugar-containing 

 yeast extracts. From the following data^ it is apparent that 

 the addition of sugar alone increases the C02-production of 

 wheat embryos. 



C02-production of Soaked Wheat Embryos. 

 A. In water. B. In a 5% sugar solution. 



86.4 mg. 133-9 mg- 



5. ANALYTICAL METHODS FOR THE DETERMINATION OF 

 OXYGEN RESPIRATION 



If one wishes to make sure that plants liberate CO2 the mate- 

 rial to be studied is placed in a special container (see below) 

 and COo-free air is passed through it. The current of ai^ 



1 Kostytschew, S. Biochem. Z. 15: 164. 1908. 



