EFFECT OF MANGANESE EXCESS ON THE SOYBEAN PLANT CULTIVATED UNDER VARIOUS GROWTH-CONDITIONS

A histological method and elemental analysis were applied to study the reaction of soybean (Glycine max (L.) Men.), cultivar 'Maple Arrow', to high manganese (Mn) supply under various growth conditions. The main impact of Mn toxicity was seen on the above ground parts of the plant. The brown fleckes on the old leaves and young apical crinkle leaf with chlorotic spots was identified as typical Mn toxicity symptoms. The chloroplasts of the Mn-toxic plant cultivated in the growth chamber accumulated large starch granules, which on the contrary represented an intensive growth of the plants grown in the greenhouse. Leaf Mn content of 2.80 mg/g did not decrease the dry weight of the older leaves, but 1.53 mg/g depressed severely that of the young leaves. The dry weight of pods was also significantly decreased.