WATER CONTENT AND ASH OF PLANTS 



169 



219. Phosphorus, in the form of phosphates, is found 

 in all parts of plants. It is one of the essential elements 

 for plant growth. Its function is to aid in the produc- 

 tion and transportation of the proteid bodies. The phos- 

 phorus and nitrogen compounds are closely associated in 

 the work of producing proteids which can take place only 

 in the plant cells. The proteid compounds produced in 

 the leaves of plants are finally transported to the seed. 

 Many proteids which are insoluble in water are soluble 

 in the presence of phosphate compounds. The phos- 

 phates are essential in the early stages 

 of the plant's development. In the case 

 of wheat, 80 per cent, is assimilated in 

 the first fifty days, and in other crops, 

 the assimilation is equally rapid. The 

 phosphates accumulate to a greater extent 

 in the seeds of grains than in the leaves 

 and stems. From 60 to 75 per cent, of 

 the total phosphates is removed in the 

 seeds. The loss of phosphates from the 

 farm is one of the reasons why soils de- 

 cline in fertility. 



Experiment 43. Phosphoric acid in seeds. 

 Crush 25 kernels of wheat in a mortar. Place 

 the crushed wheat in a small Hessian crucible 

 and ignite; when cool, transfer the charred 

 mass to a small beaker. Add 10 cc. HNO 3 and 



50 cc. H 2 O, and boil ten minutes. Break up the 



' . . .^ ... . , . Fig. 71. Plants grown 



charred particles with a stirring rod during with and without 

 the boiling. If the beaker shows signs of be- Phosphoric acid, 

 coming dry, add a little hot water. Filter. To half the filtrate, 



