CHAPTER IX 

 ABSORPTION TISSUES 



The great majority of plants are dependent for 

 their nutrients upon materials contained in the soil 

 and in the air. The nutritive processes of plants 

 differ from those of animals in that the former manu- 

 facture nutrients from compounds of very simple 

 chemical composition, as water, oxygen, carbon dioxide 

 and inorganic salts. Animals are ultimately depend- 

 ent upon the nutrients built up by plants, because 

 the nutrition processes of animals involve a breaking 

 down of the complex, substances manufactured by 

 plants. The plant is provided with special organs 

 for the ready absorption of water from the soil and 

 gases from the air. 



ABSORPTION OF WATER 



As previously noted, the primary root tissues in 

 the dermatogen zone are root cap, root hairs and 

 epidermis. The root cap cells protect the delicate 

 root tissues from injury through contact with sharp 

 soil particles. The cells of the root cap are rather 

 thick-walled and play no part in the absorption of 

 materials from the soil. The epidermal cells of the 

 root are also thick-walled and are more or less impervi- 

 ous to water. The root hairs are directly concerned 

 in the work of absorbing water, which holds in solu- 

 tion the salts occurring in the soil. These hair-like 



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