78 



PLANT PHYSIOLOGY 



A general picture of the metabolism of reserve substances is 

 presented in the diagram in Fig. 16, borrowed from one of the 

 papers by Prianishnikov. This diagram shows very clearly that 

 the total amount of nitrogenous substances remains nearly 

 constant even during a comparatively long germination period 

 in the dark, in spite of the intense disintegration of proteins. 

 The only change that takes place in this group of substances is 

 the accumulation of amino acids and asparagine in exchange for 



20 

 DajfS 



Fig. 16. — The transformation of reserve substances during the germination of 



vetch seeds {diagram after Prianishnikov) . 



the disintegrated proteins. Quite a different picture is presented 

 by the carbohydrates. A rapid decomposition of starch takes 

 place, but there is no accumulation of soluble sugar to correspond 

 to the accumulation of amino acids; their quantity remains 

 constant. The cause of this difference lies in the fact that the 

 products of hydrolysis of starch are rapidly utilized in the process 

 of respiration, which is very intense in germinating seeds. 

 Almost the total decrease in dry weight of seeds that may be 

 observed during the period of germination and that is repre- 

 sented in our diagram in the form of a shaded wedge at the top, 

 corresponds to the amount of carbohydrates utilized in respira- 



