Lecture 5. 



THE GROWTH OF PLANTS IN ARTIFICIAL 



MEDIA IN RELATION TO THE STUDY 



OF PLANT NUTRITION 



In the preceding lectures I have frequently re- 

 ferred to experiments in which plants are grown in 

 culture solutions by the so-called water-culture method. 

 In the present lecture I shall consider this method 

 more specifically and with reference to its role in 

 aiding in the elucidation of some general problems 

 of plant nutrition. Knowledge has long been avail- 

 able that at least most kinds of higher plants that 

 normally inhabit the soil, can be grown in a simple 

 solution of nutrient salts. The earliest scientific 

 record of what might be regarded as a crude water- 

 culture experiment was published in 1699 by Wood- 

 ward who grew plants in rain and river water with 

 and without the addition of a little soil. The prin- 

 ciples of plant nutrition were shrouded in obscurity 

 in those days and Woodward's technique did not lead 

 to any fruitful consequences. With the later clarifica- 

 tion of the basic concepts of plant nutrition systematic 

 work with nutrient solutions was carried on by Sachs 

 and Knop about 1860. Despite its long history, the 

 water-culture method and its close ally, the pure sand- 

 culture, remain of great service as tools for research 

 in plant nutrition. Techniques have been extended 

 and new methods of studying plants grown under 

 conditions of nutrient solution control have been in- 

 troduced. Advances in biochemistry open a wider 



