ORIGIN IN THE SEED 95 



vegetative side similar changes occur. Chibnall,* working 

 on the protein metabolism of the runner bean, found that the 

 decomposition products of the proteins of the leaf consist of 

 asparagine and other bodies containing free amino nitrogen. 

 He considers that asparagine is the chief form in which nitro- 

 gen in a state capable of resynthesis is translocated through 

 the plant. Detached leaves kept with their petioles in water, 

 translocation thereby being excluded, contain, after a few 

 days, little or no asparagine, whilst other amide nitrogen is 

 more abundant than in the leaves attached to the plant. 



The consideration of these facts fully warrants the con- 

 clusion that in the plant proteolysis yields amino acids with 

 amides, especially in the form of asparagine, of, possibly, 

 secondary origin. Does a reversal of this sequence occur 

 when proteins are laid down as reserves in storage organs ? 



THE ORIGIN OF PROTEIN IN THE SEED. 

 From the facts of animal physiology there is no doubt that 

 amino acids, the products of the hydrolysis of protein food in 

 the alimentary tract, are reconstructed to form protein in the 

 various tissues after their passage through the walls of the 

 intestine into the blood stream. There is reason to suppose 

 that the same sequence obtains in the plant. Thus Zaleski f 

 found that during the ripening of pea seeds there is an in- 

 crease in the amount of the protein at the expense of the amino 

 acids and organic bases, as is indicated by nitrogen determina- 

 tion of these compounds. 



The results were not so well marked for all seeds ; thus 

 in similar conditions but little protein synthesis took place 



* Chibnall : " Biochem. Journ.," 1924, 18, 387, 395, 405. 

 t Zaleski : " Ber. deut. bot. Gesells.," 1905. 23, 126; ' Beih. bot. 

 Zentrbl.," 191 1, 27, 63. 



