384 Mineral Nutrition of Plants 



be due instead to a diminution in demand due to a decreased rate of 

 growth. 



The experimental results here summarized have been obtained almost 

 wholly with herbaceous plants; the pineapple, guayule, and tung tree are 

 the only exceptions. Analytical results for the tung tree disagreed in 

 many respects with those for herbaceous plants. A decision on whether 

 this disagreement is caused by an intrinsic difference in metabolism 

 between these two types of vegetation must await the accumulation of 

 data on a large variety of trees. 



SUMMARY 



Mineral deficiencies in plants appear to lead to a relative accumula- 

 tion of amino acids and reducing sugars. Protein may or may not de- 

 crease depending on the extent and duration of deficiencies. Accumula- 

 tion of nitrates appears to be a result of diminished growth with mineral 

 deficiency, except in the case of molybdenum. The alterations in propor- 

 tions of nitrogen fractions lead to the assumption that all minerals 

 participate directly or indirectly in nitrogen metabolism. Carbohydrates 

 may temporarily accumulate during the early stages of deficiency. 

 Evidence exists for a localization effect in that plant parts show a de- 

 gree of parallelism between severity of visual and chemical symptoms. 

 It appears useless to attempt to draw any connection between indi- 

 vidual deficiencies and physiological responses in the plant, since pro- 

 tein metabolism is a basic reaction for all. 



REFERENCES 



1. Bennett, J. P., Minor Elements. Evidence and Concepts on Functions, 

 Deficiencies, and Excesses. Ed. by Firman E. Bear and Herminie 

 Broedel Kitchen. (Baltimore, Md., 1945). 



2. Breon, W. S., and Gillam, W. S., Plant Physiol., 19:649 (1944). 



3. Briggs, George B., Plant Physiol., 18:415 (1943). 



4. Burrell, R. C., Hotan. Gaz., 82:320 (1926). 



5. Calvin, M., and Benson, A. A., Science, 107:476 (1948). 



6. Chibnall, Albert Charles, Protein Metabolism in the Plant (New 

 Haven, Yale Univ. Press, 1939). 



7. Cooil, Bruce J., and Slattery, M. C, Plant Physiol., 23:425 (1948). 



8. Drosdoef, Matthew, Sell, Harold M., and Gilbert, Seymour G., 

 Plant Physiol., 22:538 (1947). 



