214 



PHYSIOLOGY OF NUTRITION 



Plant 



Sedum hvbridum. 



Pelargonium zonale. 



I 



Temperature fluctuations themselves exert great influence upon plant respi- 

 ration, aside from the effect produced by altered temperature. Palladin 1 

 exposed three similar lots of tips of etiolated bean seedlings to three different 

 temperatures, respectively, and then brought them all to the same medium tem- 

 perature and determined the rate of evolution of carbon dioxide in each case. 

 The following table illustrates the kind of results obtained. 



Previous 



Temperature, 



deg. C. 



Relative Amounts of C0 2 Produced per 

 Unit of Time, i8-2 2°C. 



Average 



Excess, 

 Per Cent. 



Medium, 17-20 

 Low, 7-12 



High, 36-37 



54-5, 53-5, 55o, 44-9, 58.1, 65.3, 59.8, 

 89.8, 73.6, 80.2, 53.9, 78.9, 87.4, 82.9, 

 81.4, 89.4, 



55-8 

 78.1 

 85-4 



40 



53 



The tips that remained at medium temperature formed the least carbon dioxide, 

 but those that had been recently transferred from lower to higher or from higher 

 to lower temperature produced much more of this gas. 



A very peculiar influence of temperature upon the respiration and vital 

 activity of Aspergillus niger was observed by A. Rikhter. 2 Frozen mycelium 

 of this fungus, when allowed to thaw at room temperature, appeared to have 

 been killed, and produced no trace of carbon dioxide. When the frozen fila- 

 ments were transferred directly to a temperature of 30°C, however, this gas 

 began to be given off. The rate of evolution of the gas increased gradually and 

 spores were formed. This shows that freezing is not fatal, per se; death is of 

 later occurrence, with the thawing of the organism, under unfavorable tempera- 

 ture conditions. 



An indirect relation between light conditions and respiration was discovered 

 by Borodin, 3 who found that the intensity of respiratory activity in leafy twigs 

 gradually decreases after the twigs are placed in darkness, and rises again after 

 they have been once more illuminated. These phenomena may be interpreted 

 as follows: Carbohydrates are necessary for respiration and are gradually used 



1 Palladin, W., Influence des changements de temperature sur la respiration des plantes. Rev. gen 



bot. 11: 241-257- 1899. 



2 Richter, A., Zur Frage iiber den Tod von Pflanzen infolge niedriger Temperatur. (Kalteresistenz von 



Aspergillus niger.) Centralbl. Bakt. //, 28: 617-624. 1910. 



3 Borodin, J. P., Physiologische Untersuchungen iiber die Atmung beblatterter Sprosse. St. Petersburg, 

 1876.* [Idem, Sur la respiration des plantes pendant leur germination. Florence, I875-] 



