ASSIMILATION OF CARBON 3 1 



The formation of formaldehyde was hmited by the last three (secondary) 

 reactions; hydrogen combined more easily with oxygen, to form hydrogen 

 peroxide, than with carbon monoxide. To obtain formaldehyde in greater 

 quantity Lob added a reducing agent (salicylic aldehyde, pyrogallol or 

 chlorophyll). Gly colic aldehyde (which represents the simplest sugar), as well 

 as formic acid and formaldehyde, arises from the action of the silent discharge 

 upon carbon monoxide, water, and hydrogen; 2(H2 + CO) = CH2OH — 

 CHO (glycolic aldehyde). By the concentration of its solution in vacuo this 

 substance is readily transformed into a tetrose or hexose.^ 



Stoklasa and Zdobnicky^ found that formaldehyde was formed by the action 

 of ultra-violet light upon water vapor and carbon dioxide in the presence of 

 potassium hydroxide, but no carbohydrates were thus produced. Sugar was 

 formed, however, under these same conditions, when hydrogen was present in 

 the nascent state.' 



Sorbose is formed by the action of Ught upon a mixture of formaldehyde 

 and oxalic acid.' 



Bonnier and Mangin, as has already been mentioned (see page 4), have 

 shown that if the interchange of gases accompanying the process of photosyn- 



CO 



thesis is determined independently of respiration, the ratio ~pr^ is found to be 



U2 



somewhat less than unity. From this we must suppose that substances other 

 than carbohydrates and less easily oxidized than these, are formed in the leaves 

 under the influence of sunhght. The supposition that proteins also arise in the 

 process of photosynthesis has been frequently advanced. This is supported 

 by the quantitiative researches of Sapozhnikov,* in which he estabhshed the 

 fact that an increase in protein occurs parallel with the accumulation of carbo- 

 hydrates in light. Posternak' is of the opinion that oxymethyl-phosphoric 

 acid is also formed in leaves in the presence of Jight. 



^ Bach, A., Sur revolution biochimique du carbone. Arch. sci. phys. et nat. 5: 401-41S, 520-535, 

 1898. This deals with the theory of photosynthesis. 



2 Stoklasa, J., and Zdobnicky, W., Photochemische Synthase der Kohlenhydrate aus Kohlensaurean- 

 hydrid und Wasserstoff in Abwesenheit von Chlorophyll. Biochem. Zeitsch. 30 : 433-456. 191 1. 



3 Inghilleri, Giuseppe, Photochemische Synthese der Kohlenhydrate. I. Mitteilung. Bildung von 

 Sorbose. Zeitsch. physiol. Chem. 71 : 105—109. 1911. 



* Saposchnikoff, W., Bildung und Wanderung der Kohlenhydrate in den Laubblattern. Ber. Deutsch, 

 Bot. Ges. 8: 233-242. 1890. Idem, Beitrag zur Kenntniss der Grenzen der Anhaufung von Kohlenhy- 

 draten in den Blattem. Ibid. 11: 391-393. 1893. Idem, Eiweissstoffe und Kohlenhydrate der grunen 

 Blatter als Assimilations-producte. 61 p. Tomsk, 1894. [Russian.] [Rev. by Rothert in: Bot. Centralbl. 

 63: 246-251. I895-I 



6 Posternak, S., Contribution k I'^tude chimique de I'assimilation chlorophyllienne. Sur le premier 

 produit d'organization de Tacide phosphorique dans les plantes k chlorophylle avec quelques remarques sur 

 le r61e physiologique de Tinosite. Rev. g6n. bot. 12: 5—24, 65—73. 1900. 



' Further, on the artificial formation of formaldehyde, etc., from carbon dioxide and water, 

 see: Berthelot, D., and Gaudichon, H., Synthese photochimique des hydrates de carbone aux 

 depens des Elements de I'anhydride carbonique et de la vapeur de I'eau, en I'absence de chloro- 

 phylle; synthese photochimique des composes quartenaires. Compt. rend. Paris 150 : i6go- 

 1693. 1910. For a review of this general subject, see: Spoehr, H. A., Theories of photosyn- 

 thesis. Plant world 19 : 1-16. 1916. It should be remembered that the reactions that take 

 place in leaves may not be the same as those studied in mtro. Very little experimental work 

 has been done on the photochemical changes to which chlorophyll itself is subject. — Ed. 



