MANGANESE TOXICITY IN TRIFOLIUM-BALANSAE, T-RESUPINATUM, T-SUBTERRANEUM, MEDICAGO-MUREX, M-POLYMORPHA, M-SATIVA, LOTUS-PEDUNCULATUS, AND ORNITHOPUS-COMPRESSUS - RELATIVE TOLERANCE AND CRITICAL TOXICITY CONCENTRATIONS

This paper describes the tolerance to high concentrations of manganese (Mn) of pasture legumes that are suitable for the >500 mm rainfall zo ne in southern Australia. The legumes are lucerne (Medicago sativa), b urr medic (M. polymorpha), murex medic (M. murex), balansa clover (Tri folium balansae), Persian clover (T. resupinatum), subterranean clover (T. subterraneum), greater lotus (Lotus pedunculatus), and seradella (Ornithopus compressus). Wheat (Triticum aestivum) cv. Egret and subte rranean clover cvv. Mt Barker and Karridale were included to place the tolerance of the remaining species in the context of other studies. S ymptoms of toxicity differed between species. Species ranking (in desc ending order) for Mn tolerance, and external threshold Mn concentratio ns (mmol/L), were subterranean clover (1.0), wheat (0.71), balansa clo ver (0.54), greater lotus (0.51), serradella (0.50), Persian clover (0 .25), murex medic (0.24), burr medic (0.20), and lucerne (0.19). Criti cal toxicity concentrations derived from the relationships of yields t o Mn concentrations in whole shoots for each species were as follows ( mg Mn/kg DW): subterranean clover (2010), balansa clover (1330), serra della (1080), greater lotus (760), wheat (570), burr medic (440), mure x medic (430), Persian clover (360), lucerne (190).