MANGANESE TOXICITY IN ECHINOCHLOA COLONA: EFFECTS OF DIVALENT MANGANESE ON GROWTH AND DEVELOPMENT

Abstract

Manganese (Mn2+) toxicity is probably the second most important growth-limiting factor (after aluminum toxicity) for plants in acidic soils. The objective of our study was to determine the toxic effects of different concentrations of divalent Mn (MnCl2) on the growth of Echinochloa colona in hydroponic culture. Seed germination was not inhibited by Mn concentrations of 9.1 to 910 μM in distilled water. However, the higher Mn concentration (910 μM) in nutrient solution completely suppressed root development. Although chlorophyll content decreased with increased Mn concentrations in solution, dry weights of shoots were increased by the higher Mn treatments. These treatments also produced toxicity symptoms of leaf chlorosis and necrosis. Histological studies showed that the higher Mn concentrations caused disorganization of conductive and mesophyll tissues.