158 Carbon Assimilation. 



C. Suggestion of van't Hoff. 



Baeyer's hypothesis is based on the synthesis of carbohydrates 

 in the laboratory by ordinary chemical processes. It is difBcult, 

 as we have pointed out, to imagine that the laboratory conditions 

 required for this synthesis should he comparable with those in the 

 plant. Much more stimulating and interesting therefore, is the 

 suggestion of van't Hoff that the reversible enzyme action is a 

 characteristic of many reactions in the plant. It is not clear from 

 the few remarks of van't Hoff in what manner he thought the 

 photochemical reaction and synthetic enzyme reaction should 

 co-operate in the production of carbohydrates. His main interest 

 appears to have centred on the problem as to the substances from 

 which the main products of assimilation could have been synthesized 

 by enzyme reaction. So for instance at a lecture in Diisseldorf in 

 1898, he said " It was pointed out by Tammann that under the 

 action of emulsin, amygdalin is only partially split and that this 

 hydrolysis proceeds further if the products are removed. Perhaps 

 if he had added a further amount of products of hydrolysis, he 

 might have succeeded in synthesizing amygdalin. Duclaux put 

 forward transformation formulae, which again suggest the attainment 

 of an equilibrium, and Hill seems to have effected the synthesis of 

 maltose from glucose by means of a yeast enzyme. Unless a 

 ferment undergoes alteration of some kind during its period of 

 activity, it follows, on theoretical grounds, that a condition of 

 equilibrium and not one of total change must be brought about, 

 and that therefore the opposite reaction must be induced. We are 

 indeed justified in asking the question, whether (by application of the 

 theory of equilibrium J, under the influence of zymase and by exceeding 

 a certain limiting opposing pressure of carbon dioxide, glucose might 

 not be formed from alcohol and carbon dioxide, and moreover 

 whether trypsin may not be able, under conditions prescribed by 

 the theory of equilibrium, to form protein from the products of the 

 hydrolysis, which it brings about under other conditions." (Bayliss' 

 translation, 1914; the italics are our own.) 



It is to be regretted that this suggestion has not attracted the 

 attention of plant physiologists as work on the lines indicated by 

 van't Hoff's suggestion, would at least have been likely to result in 

 lasting contributions to our knowledge of plant processes. Such 

 work is of course considerably more difficult that the carrying out 

 of qualitative tests for formaldehyde, which constitutes the bulk 

 of the work done on behalf of Baeyer's hypothesis. 



