Hoagland —56— Plant Nutrition 



of the influence of various factors on salt accumula- 

 tion. The roots of barley plants approximately three 

 weeks old that possessed this high capacity for salt 

 accumulation were initially low in salt, but not starved 

 to the point of injury or diminished root growth. They 

 had a high initial sugar content. This status of the 

 roots was the result of the regulation of the amounts 



JAN. MAR. MAY JULY SEPT NOV. JAM 



Textfigure 9. — Relative fresh weight of roots and shoots 

 of young barley plants grown by the same technique for equal 

 periods of time at different seasons of the year in a greenhouse 

 (Berkeley, California). The composition and volume of nutrient 

 solution were constant. There is reason to believe that the large 

 changes in root-shoot ratios were largely dependent on the vary- 

 ing intensity and quality of the illumination. At certain periods 

 of high illumination weights of the roots equal or exceed those 

 of the shoots. 



of nutrient salts made available during the preparatory 

 growth period, and the selection of a suitable period 

 of time for the latter. Not only entire root systems, 

 but also single unbranched roots can be investigated 

 by appropriate technique. (See plates 17 and 18). 



It should be added that the most active salt absorb- 

 ing roots were produced only during the seasons of 

 good light. It is something of a digression from my 

 main theme, but it is of interest to note that the 



