472 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 8 



There is no magic in the growth of plants in water culture. This is 

 only another way of supplying water and essential mineral elements 

 to the plant. Land plants have become adapted to growing in soils 

 during their evolutionary history, and it is not reasonable to expect 

 some extraordinary increase in their potentialities for growth as a 

 result of the substitution of an artificial medium for a soil. If no 

 toxic conditions are present and a fully adequate supply of water, 

 mineral salts, and oxygen is provided to the root system, either 

 through an artificial nutrient solution or a soil, then in the absence 

 of plant diseases and pests, the growth of a plant is limited by its 

 genetic constitution and by climatic conditions. 



NUTRITIONAL QUALITY OF PLANT PRODUCT 



Modern research on vitamins and on the role in animal nutrition 

 of mineral elements has justly aroused great public interest, but 

 unfortunately one of the results is much popular discussion of diets 

 and their influence on health which is without scientific basis. It is, 

 therefore, not unexpected that claims have been advanced that food 

 produced by the water-culture method is superior to that produced 

 by soil. 



As part of our investigation, careful studies of chemical composition 

 and general quality have been made on tomatoes of several varieties 

 grown in fertile soil and in water-culture media, side by side in the 

 same greenhouse, and with the same general cultural treatment. No 

 significant difference has been discovered in the mineral content of 

 the fruit developed on plants grown in the two media. (There is no 

 scientific basis for referring to tomatoes grown in water culture as 

 "miner alized.") 



Neither could any significant difference be found in content of 

 vitamins (carotene, or provitamin A, and vitamin C). Tomatoes 

 harvested from the soil and water cultures could not be consistently 

 distinguished in a test of flavor and general quality. 10 



Concerning the mineral content of tomatoes, it may further be 

 added, as a point of general interest, that all tomatoes contain but 

 very small amounts of calcium and are not an important source of 

 this mineral element in the diet. 



The similarity in composition and general quality of the tomatoes 

 grown in soil and water culture in the present experiments, is explained 

 by the fact that the climate and time of harvest were comparable and 

 the supply of mineral nutrients adequate in both cases. Whether 

 plants are grown in soil or water culture, climate and time of harvest 

 are, of course, of greatest importance in influencing quality and 

 composition of plant product. 



i° The quality tests were conducted by Dr. Margaret Lee Maxwell, of the Division of Home Economics, 

 and the carotene determinations were made by Dr. Gordon Mackinney, of the Division of Fruit Products, 

 College of Agriculture. 



