2 2 PLANT RESPIRATION 



Chemical stimulation is best evoked by weak poisoning. 

 The strength of the stimulant in this case can be altered as 

 desired by the administration of various amounts of the poison. 

 The effects of toxic substances on the oxygen respiration of 

 plants have not yielded the same results in the experiments 

 of various investigators.^ In fairly weak narcosis the rate of 

 respiration increases and remains a long time in the stimulated 

 condition, after which it finally returns to the normal condition. - 

 With stronger poisoning the increase in respiration is accom- 

 panied by a subsequent decrease.^ Strong poisons applied in 

 sufficiently large quantities effect an immediate marked 

 decrease in respiration.'* Under the influence of hydrogen 

 cyanide the output of CO2 in some cases is entirely suspended 

 without death ensuing. The absorption of oxygen continues 

 to a small extent and after some time returns to normal if the 

 poison is removed.^ After a prolonged stay in an oxygen free 

 medium, the mold Aspergillus niger is so badly poisoned by the 

 products of anaerobic metabolism that the gas exchange 

 becomes nil although the fungus is not yet killed.^ 



The following table, taken from the extensive monograph 

 by Morkowin,' illustrates the strongest increases in respiratory 

 energy induced by toxic substances. 



Plant Material 



Not Stimulated Stimulated 



Etiol. leaves of Lupiniis 124 



Etiol. leaves of Vicia Faba 160 



Etiol. leaves of Vicia Faba 189 



Etiol. leaves of Vicia Faba 82 



Etiol. leaves of Vicia Faba 49 



Etiol. leaves of Vicia Faba 39 



Etiol. leaves of Vicia Faba 45 



CO2 IN Mg. CO; IN Mg. Stimulant 



9 242 . 6 Paraldehyde 



4 296.3 Ether 

 9 229.5 Pyridine 



5 178.2 Cocaine 

 3 89 . 3 Morphine 

 7 105.6 Quinine 



6 97-8 Solanin 



■ Elfving. Ofvers. af Finska Vet. Soc. Vol. 28. 1886; Johannsen. Bot. Zentralbl. 68: 

 337. 189O; Morkowin, N. Der Einfluss von anasthetischen und giftigen Stoffen auf die 

 Pflanzenatmung. 1901. Russian; Jacobi, B. Flora. 86: 289. 1899. 



2 Irving, A. Ann. of Bot. 25: 1077. 191 1; Thoday, D. Ibid. 27: 697. 1913; Haas, A. 

 R. C. Bot. Gaz. 67: 377- ipiP- 



■ Zaleski, W. Zur Frage der Einwirkung von Reizstoflfen auf die Pflanzenatmung. 1907. 

 Russian. [This behavior is also reported in the papers mentioned in the editorial note on 

 the preceding page.) 



* Warburg, O. Z. f. physiol. Chem. 79: 421. 191 2. 

 ^ Schroeder, H. Jahrb. f. wiss. Bot. 44: 409. 1907. 



' Kostytschew, S. Untersuch. iiber die anaerobe Atmung der Pflanzen. 1907. Russian. 

 ' Morkowin, N. Der Einfluss von anasthetischen und giftigen Stoffen auf die Pflanzenat- 

 mung. 1901. Russian. 



