The Effect of Silicon on Yield and Manganese-54 Uptake and Distribution in the Leaves of Barley Plants Grown in Culture Solutions.

Abstract

Mn was found to be toxic to barley plants when grown in Hoagland culture solutions at Mn concentrations of 0.5 to 5.0 ppm. The necrotic symptoms are small dark, brown spots which first appear at the tips of the older leaves and spread down the leaf until the entire blade is covered. This necrosis may be alleviated by increasing the macro-salt concentration, decreasing the micro-salt concentration, especially Mn, or by the addition of soluble silicates to the culture solutions. In all cases a decrease in the amount of necrosis is associated with an increase in yield. Unlike Ca, Mg, and K which eliminate Mn toxicity by repressing the amount of Mn moving into the leaf, silicon has no effect on the content of Mn in the leaf. Radioautographs of barley leaves were taken from plants grown in culture solutions containing Mn54 in the presence and absence of Si. A comparison of the radioautographs with photographs of the same leaf areas showed a direct correlation between the presence of radioactive islands and the visible necrotic spots. In the presence of Si, however, no radioactive islands were visible, and the radioautographs showed Mn to be uniformly distributed throughout the leaf.