PERMENTATION AND RESPIRATION 



191 



Plant 



Sedum hyhridum 



Pelargonium zonule. 



Temperature fluctuations themselves exert great influence upon plant respi- 

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

 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. 



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 pecuHar influence of temperature upon the respiration and vital 

 activity of Aspergillus niger was observed by A. Rikhter.^ 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 filaments 

 were transferred directly to a temperature of 3o°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 oc- 

 currence, with the thawing of the organism under unfavorable temperature 

 conditions. 



An indirect relation between Ught conditions and respiration was discovered 

 by Borodin,' 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 up 

 during the period of darkness, so that respiration is at length retarded because 



' Palladin, W., Influence des changements de temperature sur la respiration des plantea. Rev. gin 

 bot. II : 241-357. 1899. 



" Richter, A., Zur Frage aber den Tod von Pflanzen infolge niedriger Temperatur. (K&lteresistenz von 

 Aipergillus niger.) Centralbl. Bakt. II, 28: 617-624. i9io. 



» Boiodin, J. P., Physiologische Untersuchungen fiber die Atmung beblatterter Sprosse. St. PeterBburg, 

 1876.* [Idem, Sur la respiration des plantes pendant leur germination. Florence, 187S. 



