Concentration of Nutrient Solutions [424 



Concentration., Dry Weight, Tops. Transpiration. 



atm. grants^ GO. 



0.5 0.926 651 



1.0 0.947 618 

 1.6 ' 1.152 646 

 2.5 1.117 554 

 3.5 1.030 468 

 4.5 0.904 386 

 5.5 0.821 311 



7.0 1 0.769 246 



For this particular set of salt proportions the maximum 

 yield of tops was obtained when the nutrient solution had a 

 total osmotic concentration of 1.6 atm. With lower con- 

 centrations growth was considerably less, as is also true, and 

 to a greater degree, with concentrations above the optimum. 

 Between the concentrations 1.6 and 7.0 atm. the dry weight 

 of tops is approximately a linear function of the concentra- 

 tion, the dry weight decreasing as the concentration increases. 

 The transpiration values show the same general relation to- 

 the concentration, except that below 1.6 atm. the decrease is 

 less clearly shown; in fact, with a concentration of 0.5 atm.. 

 the transpiration is slightly higher than with 1.6 atm. 



In the second series the culture solutions were the same 

 as those just described, except that KC1 was not included, 

 In these cultures the relations of dry weight and transpira- 

 tion, to total concentration, were essentially the same as in 

 the cultures of the first series, with KC1. 



In the third series the salts used were the same as in the 

 first, but in different relative molecular proportions, as fol- 

 lows : 1.000, 1.155, 7.282, 0.699. The relation between trans- 

 piration and concentration was the same as in the first series, 

 but in this case there was a perfectly definite maximum of 

 transpiration at 1.6 atm. For production of dry weight of 

 tops, however, while the general relation to concentration was 

 the same as in the first two series, the optimum concentra- 

 tion was 4.5 instead of 1.6 atm. 



The interesting features of these results may be summar- 

 ized as follows: (1) Transpiration and dry weight showed 

 an approximately linear relation to the concentration of the 

 medium above the optimum, these decreasing with an increase 

 in concentration. (2) The optimum concentration for dry 



