Plant physiologists throughout the years have used various substrates in an attempt to secure one which would give plant responses comparable to those of soil. Plants grown in water culture method, as practiced by the physiologist of the nineteenth century, showed little correlation with those grown in solid substrates or soil. Plants grown in chemically inert sand give results closer to those in soil but serious limitations are still encountered. In recent years gravel and other coarse mineral materials have been employed and the plant growth responses obtained correlate quite closely with those found when soil is used. Certain disadvantages have been found with many mineral media which are not totally inert, physically or chemically. Often the physical phenomena of adsorption and ionic replacement have been found to seriously alter the composition of the nutrient solution when mineral substrate is used. The bringing of the mineral into soluble form by the root acid has also been a definite drawback.
Proceedings of the Iowa Academy of Science
©1948 Iowa Academy of Science, Inc.
McIlrath, Wayne J.
"The Nutrient Substrate in Relation to Temperature and Photoperiodic Responses of Spinach,"
Proceedings of the Iowa Academy of Science, 55(1), 185-197.
Available at: https://scholarworks.uni.edu/pias/vol55/iss1/24