Iron phosphate precipitation in Murashige and Skoog media

Abstract

Murashige and Skoog revised medium, a standard plant tissue culture medium, precipitated on keeping because iron was ineffectively chelated. Most of the precipitate formed after two days and analysis indicated that it was predominantly iron phosphate. It was found that, after precipitation, the supernatant medium had lost c. 45% of its original iron, 20% zinc and 13% phosphate. The following modifications prevented precipitation: lowering the pH to below 3.2, increasing to 3 the molar ratio of EDTA:Fe or preparing the stock solution of FeEDTA with inadequate heating. Most of these modifications had a deleterious effect on the growth and greening of Ocimum basilicum suspension cultures. However, when an increase in the molar ratio of EDTA:Fe was achieved by reducing the iron concentration to one‐third, there was no inhibitory effect on growth or greening of these suspension cultures.