Metal Interrelationships in Plant Nutrition

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Abstract
Sugar beet and spinach beet were grown in sand culture with different sources of nitrogen or iron and different levels of molybdenum and heavy metals. Chlorophyll and some magnesium fractions were determined. Extra molybdenum accentuated chlorosis caused by excess of Mn++, Cr+++, Zn++, and Cu++ and decreased it in the presence of CrO4−− with nitrate. In the presence of these ions urea reduced chlorophyll in young and increased it in old leaves of sugar beet. Effects of urea and molybdenum were additive and independent. Ammonium sulphate caused increased chlorosis of spinach beet with Mn++ and Zn++. The existence of an acetone-soluble magnesium fraction other than chlorophyll was shown. Excess Cu++ and Zn++ decreased total magnesium; Mn++ did not. Mn++ and Zn++ reduced chlorophyll, increased the non-chlorophyll acetone-soluble magnesium, but reduced other fractions. Ferrous iron ipcreased total magnesium content and also increased the acetone-soluble fractions in the presence of Mn++ and Zn++. Extra molybdenum decreased the acetone-soluble magnesium fractions but did not affect the total magnesium content. Significant interactions between Mo, N, Fe, and heavy metals were also disclosed.