66 



THE FORMATION OF PROTEIDS IN PLANT-CELLS. 



protein formation, it is not only a very suitable source of carbon 

 but also enables reductions, and finally yields tbe necessary 

 energy by supporting respiration. 



The utility of glucose (and other carbohydrates) is, however, 

 in connection with the protein still greater than mentioned. It 

 protects — in the fully developed plant at least — the protein 

 against decomposition. It seems that the action of the proteoly- 

 tic enzyme sets in here with the gradual disappearance of the 

 glucose; as for instance in the case of keeping plants in the dark. 

 If the respiration process finds for support neither fat nor sugar, 

 then the reserve protein is attacked and the amido-acids yield a 

 portion of their carbon for the wants of respiration. Another 

 portion of their carbon is transformed into form-aldehyde, their 

 nitrogen into ammonia, and from these two very reactive com- 

 pounds the innocuous asparagin is formed and stored up for later 

 use. The reserve protein supports here respiration and plays 

 therefore a role different from the case of the development 

 of a shoot or of leaf-buds, where the transportation of nitrogen is 

 the main object, where a splitting must take place to produce 

 compounds capable of osmosis. :) 



In many cases this reserve protein is in full grown plants 

 only present in form of solution in the vacuole, and may be there 

 as active or as passive albumen, the latter being easily produced 

 from the former, for instance by dilute acids, perhaps also by 

 enzymes. That the active albumen stands in close connection 

 with asparagin becomes evident in all those cases in which Boro- 

 din observed the production of asparagin during the development 

 of leaf-buds ; here this depends upon a decrease of the amount of 

 active albumen stored up in the bark of the twigs, as I have 

 ascertained by the coffein reaction (see Chapt. IV). This 

 decrease is also observed if branches of Fagus, Quercus, or Betula 

 are kept in the dark. 2) 



That the passive albumen is not formed by direct synthesis 



1) The supposition of several authors that it is the living protoplasm itself, 

 that is constantly dissociated into nitrogenous and non-nitrogenous material, the 

 latter serving for respiration, the former being reconstructed to proteids is simply 

 absurd, entirely unchemical and wholly unphysiological (see Chapt. II). 



2) This however does not exclude that the passive albumen present, serves the 

 same purpose ; moreover the active albumen is passing at first into the passive state 

 before being decomposed into different amido-products. 



