BOOKS AND CURRENT LITERATURE 



Balance in Nutrient Media. — Tottinghami has studied the influ- 

 ence exerted upon the growth of young wheat plants by a wide range 

 of proportions of component salts in nutrient solutions, and also the 

 modifications in this influence which are produced by different total 

 concentrations. The effect of chemicals upon plant growth may be 

 altered by changing either (1) the concentration of the solution, or 

 (2) the nature or proportions of the component substances. Both of 

 these considerations are dealt with in this paper. The seedlings were 

 grown in water culture, in 250 cc. wide-mouth bottles, for a period of 

 24 days. Thej^ were supported, 6 in a culture, in a newly devised 

 2-piece cork stopper. The solutions were renewed every 3 days. The 

 paper includes a very thorough review of the literature and a rather 

 complete bibliography. 



The nutrient salts used were those composing Knop's well-known 

 nutrient solution— KH2PO4 or K2HPO4, MgS04, Ca (NOs)", and KNO3. 

 A preliminary study showed that Knop's solution employing K2HPO4 

 and having a total concentration of 2.2% will stand without precipi- 

 tating for a period of 3 or 4 days, at temperatures between 20° and 

 23°C.; while when KH2PO4 was employed the maximal concentration 

 to stand for this length of time was 2.8%. The precipitate forming in 

 more concentrated solutions was found to be mainly CaS04.2 H2O. 



Tottingham's first series dealt with the effect of different total osmotic 

 concentrations of Knop's solution, these concentrations being calcu- 

 lated approximately by means of published data on electrolytic disso- 

 ciation and osmotic pressure. Nearly equal dry yields of tops were 

 obtained in solutions ranging in osmotic concentration from 0.25 to 

 3.25 atmospheres. Solutions in which KH2PO4 was used gave about 

 18% greater top yields than those in which K2HPO4 was employed. On 

 this basis, therefore, KH2PO4 was used in the following experiments. 



In the principal part of the study various proportions of the four 

 salts were employed in solutions with three different osmotic concen- 

 trations. These concentrations were chosen so as to have the medium 



• Tottingham, W. E., A quantitative chemical and physiological study of nu- 

 trient solutions for plant cultures. Physiol. Res. 1; 133-245. 1914. 



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