PHYSIOLOGY AND MINERAL NUTRITION 115 



DISCUSSION 



Physiological processes relative to vegetative growth and fruit pro- 

 duction of the peanut plant are assumed to be similar to those of many 

 other plants. If dififerences exist, they are perhaps quantitative rather 

 than qualitative. A balance of many physiological factors is necessary for 

 the production of a healthy plant with a vigorous vegetative growth, many 

 flowers, and adequate organic and inorganic reserves to support heavy 

 fruiting. Whether the physical condition of the soil has an influence on 

 penetration by the gynophore and subsequent development of the fruit is 

 unknown. It has been shown that some mineral elements are absorbed 

 by the fruiting organs and the data indicate that small amounts of available 

 calcium in the fruiting zone aid fruit development. However, most of the 

 mineral intake of the plant is by the root system. 



In most well-drained soils the penetration of roots is limited not by 

 soil conditions but by factors inherent within the plant. The data suggest 

 that the peanut plant has an extensive root system and the roots are more 

 or less continuously growing through the soil and are constantly coming 

 in contact with soil particles from which cations can be displaced and 

 absorbed. There are no data comparing the mineral uptake by the peanut 

 plant with that of other plants from the same medium. However, it ap- 

 pears that the root system of the peanut is very efifective in extracting 

 nutrients from sandy soils of low nutrient supply. Whether that effective- 

 ness is related to the nature of absorbing roots or to the extensiveness of 

 the root system of the plant or the combination of both factors is un- 

 known. 



Physiological processes related to the nutrient supply in general 

 determine the yield of field grown peanuts. The peanut is rather sensi- 

 tive to an unbalanced nutrient supply and undoubtedly the application of 

 one or two elements to the soil in some instances has produced an un- 

 favorable nutrient balance which may account for some of the conflicting 

 results of fertilizer field trials (11, 26, 39, 89) . The only pronounced yield 

 responses reported with peanuts have been on restricted areas where the 

 available soil supply of calcium (27, 54, 69, 70) , magnesium (70, 77, 78), 

 or microelements (2, 6, 36, 71) has been very low. All these facts indicate 

 the need for additional data in order to deal more effectively with the 

 complex problems of soil and plant interrelations arising in the field. 



SELECTED REFERENCES 

 (1) Albrecht, H. R. 



1944. factors influencing the effect of inoculation of peanuts grown 

 ON NEW PEANUT LANDS. Soil Sci. Soc. Amer. Proc, 8:217-220. 



