OXYGEN RESPIRATION 1 7 



as for all reactions of organic materials. Contrary to the 

 opinion of various older workers, at present it can be con- 

 sidered as proven that for plant respiration there is no opti- 

 mum temperature. The amount of the carbon dioxide given 

 off increases regularly with the gradual increase in temperature, 

 finally reaches a maximum value and remains at the same 

 level until the death of the plant from the high temperature' 

 (at about 50°). Marked temperature fluctuations eft"ect an 

 increase in the respiratory energy.^ It can hardly be doubted 

 that we have to do here with a complicated irritation effect 

 {Reizwirkung). The same explanation also holds for the 

 influence of warm baths on respiration.^ The warm bath is a 

 strong irritation effect which in horticultural practice is used 

 to shorten the latent period of winter. 



If a complete combustion of respiratory material takes place 



in respiration, -7^ remains perfectly constant for various 



temperatures.^ It does not remain so in the case of succulents, 

 which with lower temperatures effect an incomplete oxidation 

 of sugar and take in a surplus of oxygen which serves for the 

 formation of organic acids. With higher temperatures the 

 sugar is burned without a residue and the respiratory quotient 

 is equal to i.-^ 



The Influence of Light on Respiration. — The stimulatory 

 eft'ect of light on the respiration of plant parts containing 

 chlorophyll*^ is undoubtedly due to the fact that particularly 

 in the light there are formed carbohydrates which then serve as 

 respiratory material. The respiration of chlorophyll free plants 

 and plant parts is practically unaffected by light' or is some- 

 whaL retarded.^ It must be noticed, however, that all inves- 



1 Bonnier, G. et Mangin. Ann. sci. nat. Bot. (VI) 17: 210. 1884; 19: 217. 1884. 



- Palladin, W. Rev. gen. de bot. 11 : 241. 1899. 



3 Iraklionoff. Jahrb. f. wiss. Bot. 51 : 515. 1912; Arb. d. Petersb. Naturf.-Ges. 42 : 241. 

 191 1. 



' Puriewitsch, K. Ann. sci. nat. bot. (VIII) i: i. 1905. 



» Aubert, E. Rev. gen. de bot. 4: 203. 1892. 



« Borodin, J. Physiol. Untersuch. iiber die Atmung der Laubsprosse. 1876. Russian. 



' Maximow, N. Zentralbl. f. Bakt., Parasitenk. u. Infektions-krankh. (ID 9 : i93- 1902. 



s Bonnier et Mangin. Compt. rend. 96: I07S- 1883; 99: 160. 1884; 102: 123. 1886; 

 Ann. sci. nat. bot. (VI) 17: 210. 1884; 18: 293- 1884; 19: 217. 1884; Elfving. Studien 

 iiber die Einwirkung des Lichtes auf die Pflanze. 1890; Lowschin, A. Beih. z. bot. Cen- 

 tralbl. 23: 54. 1907. 



