EFFECT OF TEMPERATURE 85 



to 40 C. the amount of carbon dioxide evolved fluctuates : a 

 rapid fall occurs in the first two hours, then a rise for one or 

 two hours, followed by a continuous fall. At still higher 

 temperatures there is a continuous reduction in the evolution of 

 carbon dioxide, a result which is in accordance with the 

 observations of Blackman mentioned above. 



These observations are different to those made by Miiller- 

 Thurgau and Schneider-Orelli ; thus Kuijper observed a per- 

 manent increase in respiration after due exposure to high 

 temperatures, whilst the latter workers found a decrease to 

 obtain. This discrepancy may be due to the fact that Kuijper's 

 seedlings were subjected to the increased temperature for a 

 lesser time than the potatoes of Miiller-Thurgau and his 

 collaborator and, as has already been remarked, the material 

 employed was in active growth on the one hand whilst on the 

 other it was resting. Kuijper explains his results on the 

 hypothesis that there are two distinct processes concerned in 

 respiration which are affected differently by a continuance of 

 high temperature : one phase being early depressed whilst the 

 other is stimulated ; there is here a possible correlation with 

 the dual origin of the carbon dioxide of respiration, which, 

 according to Palladin, arise from the activity of an oxidase and 

 of a carboxylase. Like Muller-Thurgau and Schneider-Orelli, 

 Kuijper recognizes the inter-relation of temperature and the 

 nature of the available respirable material. Thus of the 

 seedlings examined, the lupin showed a rise in the respiration 

 intensity from 15 C. to 20 C., the pea from 20 C. to 25 C, 

 and the wheat at 30 C. The fluctuation period was well 

 marked at 25 C, 30 C, and 35 C. respectively and the 

 continual fall in carbon dioxide output obtained at 25 C, 

 35 C. and 40 C. respectively. Of the food available, the lupin 

 has 37 per cent, the pea 22 per cent, and the wheat 12 per 

 cent of protein, whilst of starch the lupin has none, the pea 54 

 per cent, and the wheat 74 per cent. 



If respiration be a purely chemical process, a combustion 

 of, say, sugar, Van't HofFs law should apply throughout the 

 process : the evidence shows, however, that the law is followed 

 only for lower temperatures ; at higher temperatures, as has 

 been seen, fluctuations obtain and correlation comes to an end, 

 which is indicative of the intervention of internal factors, the 



