7 8 PLANT PHYSIOLOGY 



SECTION 1. THE PROCESSES OF NUTRITION. 



The processes of Nutrition are those which concern the main- 

 tenance of the life of the individual, and therefore they deal 

 with the absorption, transformation, and release of matter and 

 of energy. They fall, for convenience of study, into two some- 

 what natural sub-sections, according as they deal mainly with 

 chemical changes or with physical movements, and they may 

 be further classified as follows: 



Sub-section A. Metabolic (chemical) processes, which include 

 changes of: 



a. CONSTRUCTION (synthesis or anabolism) of simple and stable into com- 



plex and less stable substances, with change of kinetic to potential 

 energy; occurs in plants alone. Of the substances constructed 

 there are two basal types, thus determining. 

 I. Carbohydrate construction, effected through: 



1. Photosynthesis, utilizing energy of light. 



2. Chemosynthesis, utilizing energy of chemical affinity. 

 II. Proteid construction, or 



3. Synthesis of Proteids, utilizing energy of uncertain origin. 



b. TRANSFORMATION (metabolism proper, assimilation proper) of the 



afore-mentioned synthates into related substances of special func- 

 tion, with only slight chemical, though often marked physical, 



changes, and without great change of energy relations; occurs in 

 both plants and animals. Includes but one process: 



4. Conversion, including Accumulation of reserves, and 



Secretion of substances of special function. 



c. DESTRUCTION (analysis, reduction, katabolism) of complex and less 



stable to simpler and stable substances, with change of potential 

 to kinetic energy; occurs in both plants and animals. Includes but 

 one distinct process: 



5. Respiration (Energesis), inclusive of Fermentation. 



Sub-section B. Translocatory (physical) processes, which in- 

 clude movements of: 



6. Absorption of materials into the plant. 



7. Transport of materials through the plant, including espe- 



cially: 



(a) Transfer of water, and (b) Translocation of plastic 

 substances. 



8. Elimination of substances from the plant, including Tran- 



spiration and Guttalion of water, and Excretion of 

 waste materials. 



