OPENING ADDRESS 



hy the late B. Nemec, D.Phil, 



formerly Professor of Plant Physiology, University of Prague 



It is an honour and pleasure, indeed, to open this symposium 

 on behalf of the International Union of Biological Sciences. I 

 sincerely welcome all those attending this Symposium on Trace 

 Elements in Plant Physiology. We are very glad our meeting is 

 organised in close collaboration with the Rothamsted Experimental 

 Laboratory where so much has been done to promote our knowl- 

 edge of the nutrition of plants. I wish to thank Dr. Ogg, 

 Director of the Rothamsted Laboratory, very much for his kind 

 words of welcome. 



Ninety years ago Julius Sachs began, in Prague— as private 

 assistant of T. Purkynje— his experiments on water cultures. He 

 studied the formation of lateral and adventitious roots and as he 

 saw roots growing very well in spring water, he supposed it would 

 be possible to grow plants in spring water to the ripe fruit stage. 

 He changed the water at least twice each day and was able to 

 demonstrate on the occasion of an Agricultural Congress in Prague 

 (1858) surprising results of his cultures. But it had been the 

 idea of Stockhardt in Tharandt to dissolve salts in distilled water 

 and so to determine the essentiality of some mineral elements for 

 plants. Sachs, who was appointed in 1859 as assistant at Tha- 

 randt, was soon able to demonstrate that six mineral elements (S, 

 P, K, Mg, Ca, Fe) are essential for higher plants. Water cul- 

 tures have been more useful than the sand cultures of Salm- 

 HoRSTMAR. Plant physiologists, for a long time, believed that 

 only six mineral elements were essential for plant nutrition. In 

 papers from the last century, dealing with the analysis of plant 

 ash, usually only these six elements are mentioned. In the first 

 edition of Wolff's Aschencmalysen (1871) other elements are 

 seldom mentioned. 



Meanwhile in various species and in plants from different lo- 



