SPECIALIZATION IN HIGHER PLANTS 



69 



VI. In a paragraph, discuss the functions of the vascular or conducting and 

 supporting systems of a plant, including the adaptations or specializations for 

 various functions. 



upper surface lower surface 



Most leaves are covered with a layer or layers of thick-walled cells lacking chlorophyll. 

 The lower surface of most leaves bears certain paired cells containing chloroplasts. These 

 cells permit the passage of substances in and out the leaf. They are the guard cells. 



Specialization in higher plants. Higher plants perform all 

 the physiological functions necessary for life. Each individual 

 cell performs many of these same functions, but at the same time 

 each cell is adapted to perform 



one function better than others. 

 Absorption of water and minerals 

 is performed by special epidermal 

 cells called root hairs, found on 

 the roots. These cells are long 

 and slender and grow among the 

 particles of soil. The water and 

 mineral matter pass through the 

 root hairs, then through other 

 root cells until they reach the 

 ducts (xylem) near the center of 

 the root. By means of capillary 

 action, evaporation of water from 

 the leaves, and the pressure of 

 other fluids following, the water 

 rises in the spirally-thickened 



-- chloroplasts 



wall of a 

 gccara cell 



nucleus of a 

 guocr^ ce-Il 



^xor^lcell 



A surface view and cross section of the 

 specialized epidermal cells which make a 

 passageway to the air spaces within the leaf. 



