Lecture 5 — 123 — Artificial Media 



To answer questions like these demands the application 

 of all the tools of plant nutrition, one of which is the 

 method of artificial culture. I have already spoken of 

 the Federal laboratory at Cornell University estab- 

 lished to study problems of this kind. 



In my first lecture I referred briefly to a problem 

 of concern to my own part of the United States — the 

 problem of alkali soils. Here too we must deal with 

 a multiphase system. One of the efforts must be to 

 understand the effects of the alkali salt on the plant, 

 going beyond the ordinary concentrations and ionic 

 balances of nutrient solutions. At the present time 

 sand culture methods are in use at the Federal Salinity 

 Laboratory at Riverside, California, for ascertaining 

 the tolerances of different species of plants to varied 

 concentrations of sodium salts. Installations are located 

 in three climatic areas ; namely, Riverside, the Coach- 

 ella Valley and on the coast at La Jolla. These sites 

 differ greatly in light, temperature and humidity. 



There are still other uses for controlled artificial 

 culture methods of growing plants, although some 

 of them have not yet received much general attention. 

 Considerable interest is occasionally manifested by 

 students of entomology in the possibilities of con- 

 trolling the nutrition of the plant and perhaps modify- 

 ing in a known way the ability of the plant to resist 

 insect attacks, or at least to explain a little more 

 clearly certain observations on plant-insect relations. 

 Some experimental work has been initiated. 



Plant pathologists likewise may possibly find ad- 

 vantages in a method for controlling the inorganic 

 nutrition of the plant. Sporadic observations have 

 been recorded of interrelations between the nutritional 

 status of a plant and its susceptibility to injury by 

 certain pathogenic organisms. Wheat plants grown 

 in a medium very low in silica often become highly 

 susceptible to fungus attack. Spencer (1942) has 

 suggested opportunities for the investigation of the 

 controlled nitrogen nutrition of the plant in relation 



