EFFECT OF BORON 205 



Similarly Johnston and Dore * found that for tomato 

 plants grown in water culture, normal growth is impossible 

 if boron, in the form of boric acid, is absent. In boron- 

 starved plants there is twice as much sugar in the leaves as 

 compared with plants grown in a boron-containing medium, 

 the breakdown in translocation being due presumably to the 

 disintegration of the conducting tissues. 



McHargue f found comparable effects in Glycine hispida, 

 the soy bean, when manganese was withheld from the culture 

 medium. But Brenchley and Warington found that man- 

 ganese was entirely without effect on this plant when deprived 

 of boron ; it, however, had a stimulating action on those 

 plants supplied with boron. There may be some interrelation 

 between boron and manganese such as occurs between other 

 nutrient elements.^ 



Sommer and Lipman § find that boron is essential for the 

 growth of the Windsor bean, buckwheat, flax, mustard and other 

 plants, and zinc is indispensable for the dwarf sunflower and 

 barley. 



In view of the observation || that the administration of 

 pure borax has harmful effects varying with the plant, the 

 potato for example being more resistant than maize and bean, 

 it would appear that the form in which the boron is adminis- 

 tered may be of importance. 



Mention has above been made of manganese ; this metal 

 has a wide occurrence in the plant and is possibly of universal 

 distribution ; ^[ it accumulates in those parts where metabolism 

 is most active and in those regions which are known to be 

 rich in vitamins such as the pericarp of cereal fruits.** It 

 may possibly play the part of a catalyst, an idea which is 

 supported by its association with certain oxidases. ff The 



* Johnston and Dore : " Science," 1928, 67, 324. 



f McHargue : " Journ. Agric. Res.," 1923. 37> ° 2 9- 



% See, for example, Brenchley, Maskell and Warington : " Ann. 

 Appl. Biol.," 1927, 14, 45. 



§ Sommer and Lipman : " Plant Physiol.," 1926, I, 231. 



|| Skinner, Brown and Reed : " U.S. Dept. Agric," Bull. 1126, 1923. 



I! Bertrand and Rosenblatt : " Compt. rend.," 192 1, 173, 333 I " Ann. 

 Inst. Pasteur," 1921, 35, 815. 



** McHargue : " Journ. Agric. Res.," 1924. 27, 417. 



ft See Vol. I., p. 502. 



