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JOURNAL OF AGRKMIAL RESEARCH 



Vol. XX Washington, D. C, November i, 1920 No. 3 



COMPOSITION OF NORMAL AND MOTTLED CITRUS 



LEAVES 1 



By W. P. KELLEY and A. B. Cummins, Citrus Experiment Station, College of 

 Agriculture, University of California 



INTRODUCTION 



Knowledge concerning the composition of a plant is essential to an 

 understanding of its growth. The amounts and proportions of the 

 different constituents absorbed from the soil or other nutrient medium, 

 as revealed by accurate analysis of the several parts of plants, undoubt- 

 edly give some indication concerning their nutritional requirements. If 

 determined progressively, such data may contribute to a clearer under- 

 standing of fundamental physiological processes of growth. 



The interpretation of plant analyses, so far as growth processes and 

 requirements are concerned, demands great caution, however. Many 

 plants undoubtedly have the power of adapting themselves to a wide 

 range of soil variations; and the composition of the plant, owing to 

 selective absorption, commonly bears little direct relation to the com- 

 position of the nutrient solution. It is well known that the concentration 

 of a given constituent in the nutrient solution may be varied considerably 

 without producing any material change in the composition of the plant. 



The effect of an excess or deficiency of one ion on the absorption of 

 other ions, and especially the effects of nonessential salts on the absorption 

 of essential ions, have not been sufficiently studied. Despite the many 

 investigations during recent years on antagonism, comparatively few 

 analyses have been made showing the effects on absorption. Likewise, 

 investigations on the so-called nutritional or physiological diseases have 

 not dealt with absorption specifically, except to a very limited extent. 



Previous studies on the rate of absorption of nutrients have been con- 

 ducted mainly with annual plants, chiefly cereals, very limited study 

 having been devoted to trees. There is much need for accurate data on 



the several phases of absorption as related to the growth of fruit trees. 







1 Paper No. 67, University of California, Graduate School of Tropical Agriculture and Citrus Experiment 

 Station, Riverside, Calif. 



Journal of Agricultural Research, Vol. XX, No. 3 



— Washington, D. C Nov. 1, 1920 



vh Key No. Calif.-»4 



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