Induction of Callose Formation by Manganese in Cell Suspension Culture and Leaves of Soybean ( Glycine max L.)

Abstract

The effect of 0.02 µM–20,000 µM manganese (Mn) supply to suspension-cultured soybean ( Glycine max L.) cells in liquid B 5 medium was evaluated with respect to growth, Mn concentration, Mn oxidation and callose formation. Mn concentrations of cells as low as 1 µg Mn (g dry weight) −1 were not associated with a growth reduction over a 6-day culture period. However, higher callose concentrations were found compared with Mn concentrations of cells between 5 and 300 µg Mn (g dry weight) −1. At cell Mn concentrations higher than 300 µg Mn (g dry weight) −1 again callose synthesis was induced well before any growth reduction. In a time study with 5000 µM Mn supply, Mn oxidation was completed within the first 4 h. Later on only total cell Mn concentrations further increased up to 32,000 µg Mn (g dry weight) −1 after a 4-day culture period. No correlation existed between the degree of browning of the cells and their concentrations of oxidized Mn. The callose concentrations increased after an initial lag phase, reached a maximum after 3 days and then declined. In intact leaves of soybean plants (cv. Sito) grown in nutrient solution at Mn supplies ranging from deficiency (0.01 µM Mn) up to toxicity (100 µM), again at low and high Mn tissue concentrations, callose formation was induced. At high Mn tissue concentrations callose formation was more sensitive than visible Mn toxicity symptoms or growth effects. The comparison of cultured cells with leaves of intact plants indicated a much lower critical deficiency but higher critical toxic Mn concentrations with regard to growth and callose formation.