PLANT PHYSIOLOGY 



CHAPTER I 

 PHYSICO CHEMICAL ORGANIZATION OF THE PLANT 



1. Basic Features of the Structure of the Plant Cell. Proto- 

 plasm as the Carrier of Vital Phenomena. Proteins and Lipoids 

 as Its Chief Constituents. — The life of plants is an extremely 

 complicated chain of phenomena that are closely combined into 

 a unit of action and very finely coordinated with each other. 

 At death, this coordination is suddenly disturbed; the charac- 

 teristic process of the continuous metabolism of substances form- 

 ing the living organism becomes confused ; processes of synthesis 

 are replaced by processes of decomposition; internal physiological 

 connection between the different parts is lost; and the plant 

 desiccates or decays, becoming the prey of microorganisms. 



Such a close coordination of the most complicated changes 

 is possible only through intricate organization of the plant body. 

 Externally, this organization is manifested in the different organs 

 of the plant body; these in turn may be separated into various 

 tissues, and the tissues into separate cells. The differentiation 

 of plants into organs, tissues, and cells forms the subject of 

 courses in morphology and anatomy. A sufficiently detailed 

 acquaintance with the structure of the plant is essential for an 

 understanding of its vital functions. There will be an oppor- 

 tunity in the future to return to such details of the plant struc- 

 ture as are especially closely connected with its functions. 

 Whatever these details may be, they should not obscure the 

 general plan of construction, viz., that every part of the higher 

 plant is composed of a multitude of different kinds of cells. 

 These cells may vary in size and shape and may perform different 

 functions. 



Each cell consists of the same important parts: the cell wall; 

 and its -contents, the cytoplasmic and nuclear structures. The 

 cell wall is a sort of external skeleton of the cell, and it preserves 



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