PHYSIOLOGY AND MINERAL NUTRITION 103 



FUNCTION OF NUTRIENTS AND DEFICIENCY 

 SYMPTOMS 



The nutrients as a group are thought to have a number of general 

 roles, but in most cases it is difficult to state the exact function of a given 

 element. A deficiency of any essential element adversely afifects plant 

 growth and yields. Mineral-deficiency symptoms are rarely found with the 

 peanut when grown under field conditions but have been observed with 

 plants grown in nutrient solution. Burkhart and Collins (19) described, 

 deficiency symptoms of the Virginia Bunch peanut in the young stage, 

 while other workers (10, 37) have described the efifects of a deficiency 

 of the major elements for the Dixie Runner peanut at a later stage of 

 growth. However, the symptoms described are, at best, roughly qualita- 

 tive and in many instances are not specific. The role of nutrients in 

 peanuts is assumed to be similar to that of other plants and is discussed 

 briefly in connection with observed nutrient-deficiency symptoms. 



Nitrogen. This element is the main constituent of protoplasm and 

 occurs in a number of other organic compounds, one of the most im- 

 portant being chlorophyll. One of the main functions of nitrogen is 

 obviously its requirement for the formation of new protoplasm in growth. 

 Large amounts of nitrogen usually cause peanut plants to become dark 

 green in color, grow rapidly, producing succulent vegetation that does 

 not flower and fruit well (58). A lack of nitrogen in the peanut plant re- 

 sults in stunted growth, yellow foliage, reddish coloration of stems, and 

 few nodules are found on the roots ( 19) . 



Phosphorus. Young meristematic tissue contains considerable phos- 

 phorus where it is utilized in the growing region in the formation of 

 nucleoproteins and a number of other phosphorus compounds, including 

 important respiratory enzymes and intermediates. Without phosphorus 

 nuclear division and meristematic activity is decreased. Considerable 

 quantities are stored in fruit and seed, hence the yield and size of seed 

 may be afifected. This element hastens ipaturity and root development. 

 Peanuts with a low phosphorus content have a small leaf surface. The 

 leaves are a dull bluish green in color, and in later stages they become 

 yellowish and drop. 



Potassium. Potassium occurs largely in the plant as soluble organic 

 and inorganic salts. It is transported from the older parts to the actively 

 growing regions of the plant under conditions of potassium deficiency. 

 The exact function of potassium is obscure, but it is thought to play a part 

 in the formation and translocation of various carbohydrates, the utili- 



