The reaction of lucerne seedlings to high concentrations of manganese

Summary

Concentrations of manganese lower than 100 ppm did not induce detectable differential effects in young seedlings of lucerne. Concentrations of 400 ppm or higher were unnecessarily high for inducing differential responses.

Germination was not affected by concentrations of less than 1,000 ppm Mn.

Hundred ppm Mn retarded the rate of leaf appearance, reduced the size of the unifoliate leaf, decreased the production of dry matter, and induced toxicity symptoms.

There were no clear-cut differences between lines in the effects of manganese concentration on the rate of leaf appearance, so this character is not a reliable criterion of tolerance to manganese toxicity. However, reduction in size of the unifoliate leaf and decrease in dry weight by high concentration of Mn differentiated clearly between seedlings in their reaction to toxicity. Symptom ratings and manganese content of the shoot gave supplementary information.

Maternal influences were unimportant in assessing the reaction of lucerne seedlings to manganese toxicity, but seed size may sometimes affect characters used to measure the degree of tolerance or susceptibility.