104 THE PEANUT— THE UNPREDICTABLE LEGUME 



zation of nitrogen, and in cell division. Potassium-deficient peanut plants 

 (10, 37) have few necrotic "scorch" areas at the leaf margins. In the late 

 stages of potasium deficiency the stems near the tips of branches become 

 reddish in color, then brown, which is followed by death of the tissue. 



Calcium. Most of the calcium of plants occurs in the foliage and very 

 little is found in the seed. The peanut seed is especially low in this ele- 

 ment. Calcium-oxalate crystals are sometimes found in plant tissue. 

 Calcium is considered relatively immobile in plants. Root growth of the 

 peanut is severely affected by a shortage of calcium. A deficiency causes 

 stunting and small distorted leaves near the tips of the branches. Inter- 

 veinal brown pitted areas which coalesce to form larger necrotic spots 

 develop on the affected leaves which give the leaves a bronze color. Basal 

 stem cracks and die-back of the affected shoots occur during later stages. 

 A deficiency of calcium (27) also affects the fill and quality of peanut 

 fruit. 



Magnesium. The chlorophyll molecule contains magnesium, and since 

 a deficiency of this element results in chlorosis, it plays a part in photo- 

 synthesis. Although only a small proportion of the magnesium of the 

 leaf can be accounted for by that in the chlorophyll, a large proportion of 

 this element is carried in the green foliage, and there is a considerable 

 amount in the seed. Magnesium leaf deficiency symptoms of the peanut 

 (19) appear first as a chlorosis of margins of older leaves. In later stages 

 the leaf margins may become orange in color. Magnesium has been 

 demonstrated to be a factor in fruit production (10, 77, 78). 



Sulfur. Sulfur is well distributed in the plant in the form of proteins, 

 volatile compounds, and sulphates. Sulfur is not a part of the chlorophyll 

 molecule. However, it may be required in the process of chlorophyll 

 formation, since deficient plants have a pale green color. It seems to af- 

 fect root development and to have an important part in respiration pro- 

 cesses and cell division. The writers grew peanuts on a minus sulfur 

 nutrient solution and the plants were smaller, but no other visible de- 

 ficiency symptoms appeared. Burkhart and Collins (19) indicate that a 

 deficiency of sulfur caused the leaves to be a lighter green color. 



Iron. Plants grown on soils of high pH values frequently show 

 iron-deficiency symptoms because of its unavailability. Iron is not a part 

 of the chlorophyll molecule, and yet a deficiency results in chlorosis. It is 

 assumed to have a catalytic effect in oxidation-reduction processes within 

 cells, and it is found in enzymes. The quantity of iron present itl plants is 

 very small and it is quite immobile. Typical iron chlorosis developed 

 when peanuts were grown in Hoagland's and Arnon's nutrient solution 



