20 PLANT RESPIRATION 



rounding atmosphere.^ Protoplasmic streaming is also stopped 

 by COo.- It is worthy of note that the respiratory quotient 

 is not altered in the presence of 40% COa-^ 



The Influence of Nutrient Materials on Respiration.— Boro- 

 din^ first showed that carbohydrates, which are formed in the 

 light in green parts of plants, increase the rate of respiration. 

 Subsequently the important significance of the sugars for 

 respiration was established beyond doubt by several investi- 

 gators. Particularly instructive in this connection are the 

 experiments of Palladin^ who nourished green and etiolated 

 young leaves of various plants with solutions of sugars and 

 other organic nutrient materials and then measured the respira- 

 tory intensity of the plants. It appeared that leaves which con- 

 tain a very small supply of carbohydrates in general respire feebly. 

 The application of sugar to such leaves always effected a very 

 appreciable increase in the rate of respiration. The fluctuations 

 of the respiratory quotient as influenced by the percentage 

 composition of the organic nutrients were described above. 



The Influence of Concentrations of Various Solutions on 

 Respiration.— For molds and other lower plants growing on 

 solutions of various organic materials the concentration of 

 the solution is of salient importance. On concentrated sugar 

 solutions the respiration is generally weaker than on dilute 

 solutions. 6 The same rule was confirmed for young leaves of 

 seed-plants when they are artificially nourished with sugar." 

 The checking action of high concentrations of sugar is apparently 

 due to osmotic action. Solutions of mineral salts also produce 

 the same eft'ect.^ In other respects the action of mineral sub- 

 stances on oxygen respiration of plants is quite a compHcated 

 process. 9 Antagonism of the metallic ions [cations] plays an 



iKidd, F. Proc. Roy. Soc. London. B. 87: 609. 1914; 89: 136, 612. 1915. 



- Lopriore. Jahrb. f. wiss. Bot. 28: 571. 1895- 



3 Deherainet Maquenne. Ann. de la science agronom. frang. et dtrangere. Vol.12. 1886. 



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

 sPalladin, W. Rev. g6n. de bot. 5: 449. 1893; 6: 201. 1894; 13: 18- 1901; Maige, A. 



et G. Nicolas. Compt. rend. 147 : i39- I908; Rev. g6n. de bot. 22 : 409. 1910. 

 «Kosinski. Jahrb. f. wiss. Bot. 34: i37. 1902. 



• Palladin, W. et Komleff. Rev. g6n. de bot. 14: 497. 1902. 

 slnman, O. L. J. Gen. Physiol. 3 : 533- 1920-21. 



» Krzemiemewski. S. Bull. acad. Cracovie 1902; Zaleski, W. und Reinhard. Biochem. 

 Z.f23 : 193. 1909. [For a thorough study of the effect of various concentrations of salts of 

 the heavy metals see Cook, S. F. J. Gen. Physiol. 8: 375-601. 1925-26.] 



