TRACE ELEMENTS IN PLANTS 



115 



with Vicia Faba, Brenchley and Warington (1927) obtained 

 results that suggested an association of boron with the absorp- 

 tion or utilization of calcium. Cultures without boron and with 

 a very small supply of calcium as calcium sulphate (0-025 g. per 

 litre) made poor growth and developed very small blackened 



Table XI. Absorption by Impatiens balsamina of various ions 

 from solutions of single salts in presence and absence of 

 boron. (Data from Rehm) 



Table XII. Absorption by Impatiens balsamina of various 

 ions from solutions containing the major plant nutrients 

 with and without boron. (Data from Rehm) 



Ratio of absorption of ion with 



boron present (0-5. mg. litre) 

 to absorption with boron absent 



leaves, finally turning black at the stem apices and withering 

 backwards from these. It will be noted that these are the 

 symptoms of calcium shortage and not of boron deficiency (see 

 p. 80). The blackening is attributed to the toxic effect of other 

 nutrient salts, a toxicity which is normally counteracted by 

 calcium, and the plants probably died before even the calcium 

 in the seed was used up. In cultures containing the same supply 



