Plant structure 

 and composition 



8 



The mature plant is made up of distinct organs known as roots, 

 stems (stalks or trunks and branches), leaves, and flowers or seeds 

 surrounded by a fleshy or non-fleshy covering. In some plants under- 

 ground, or subterranean, stems enlarge and serve as food-storage 

 organs for the plant. Through the process of selection and by the ap- 

 plication of the science of genetics man has developed various plant 

 types for the production of fruits, grains, potatoes, and vegetables. 



THE CELL 



The basic unit of all these organs of the plant is the cell. The cell 

 is the seat of the physiological processes involved in plant metabolism 

 (Chapter 9) and reproduction. A representative plant cell may be 

 considered as consisting of a mass of protoplasm containing a vacuole. 

 The protoplasm is in turn surrounded by the cell wall. 



The Vacuole 



The vacuole consists largely of a water solution of inorganic anions 

 and cations and low-molecular-weight organic substances. Included 

 among the latter are sugars, amino acids, organic acids, and the water- 

 soluble anthocyanin and flavone pigments. The vacuole may be con- 

 sidered a transient depot for these organic and inorganic components, 



177 



