CHAPTER XXVI 

 Composition of Plants at Different Stages of Growth 



348. Composition and Stage of Growth. Plants do 

 not have the same chemical composition at different 

 stages of growth. The chlorophyl and protoplasm are 

 most active in the early stages and produce the nitrogenous 

 compounds more rapidly than the non-nitrogenous ones. 

 The later stages of growth are utilized mainly for the 

 production of carbohydrates and for the various chemical 

 and physical changes incident to ripening and the transfer 

 of the organic compounds from the leaves to the seeds. 

 Plants have a different food value at their different 

 stages of growth as well as a different chemical composi- 

 tion. 



349. Assimilation of flineral Food by the Wheat 

 Plant. The various elements of plant food utilized by 

 spring wheat are assimilated quite rapidly in the early 

 stages of growth. The mineral matter being essential for 

 the production of the organic compounds is taken from 

 the soil in advance of their formation. Before the crop 

 has completed the first half of its growth, over 75 per 

 cent, of the total mineral matter has been taken from the 

 soil. Of the mineral elements, phosphoric acid, potash 

 and lime are assimilated most rapidly. 



350. Assimilation of Nitrogen by the Wheat Plant. 



The nitrogen utilized by the spring wheat crop is 

 taken from the soil in advance of the mineral matter. 



