On an Important Function of Leaves. 



BY 



U. Suzuki, Nogakushi. 



It has long since been known that nitrates absorbed by plants 

 from the soil disappear rapidly in the leaves, while they are 

 found stored up for a longer or shorter period in the stem and 

 roots. It was therefore supposed by several authors that the 

 nitrates can be reduced only in the leaves, yielding thereby 

 proteids and amido-compounds. It was further asserted that 

 direct sunlight would be necessary for the reduction, and one 

 author went even so far as to assert that only the nascent 

 carbohydrates in the chlorophyll bodies could bring on the 

 assimilation of nitrates. But all these hypotheses evidently go too 

 far and have not been verified. It can easily be shown that 

 nitrates can be assimilated in darkness just as well as in day- 

 light, as has been done by Loew^^ He cultivated mould fungi 

 in a dilute solution containing glycerol, sodium nitrate, mono- 

 potassium phosphate, sodium sulphate and magnesium sulphate, 

 some of the flasks being kept in darkness, others in ordinary day- 

 light, but no essential difference was observed in the weight of the 

 fungoid mass, so that no favourable action of light upon the 

 assimilation of nitrates was noticed. Indeed there are other 

 causes which must have much influence upon the readiness 

 to assimilate the nitrates, such as the intensity of respiration 

 and the amount of glucose present, as well as the temperature. 

 Thus we can easily understand why the nitrates arc more quick- 

 ly assimilated in the leaves, whose activity consists principally 

 in the preparation of carbohydrates, and whose anatomical 

 structure permits a very lively respiration which must naturally 

 increase the energy of protoplasm in all the cells of the leaves. 

 If it can be shown that under certain conditions amido-com- 

 pounds present in roots and fruits are better sources of nitrogen 

 for protein production than the nitrates, then an important 

 function of the leaves in facilitating the protein production in all 



(I) Biolog. Cent. Bl. lo. No. 19. 



