PLANT TOLERANCE TO NICKEL TOXICITY .2. NICKEL EFFECTS ON INFLUX AND TRANSPORT OF MINERAL NUTRIENTS IN 4 PLANT-SPECIES

Nickel (Ni) is an essential micronutrient for higher plants but is tox ic to plants at excess levels. Plant species differ extensively for mi neral uptake and accumulation, and these differences often help explai n plant tolerances to mineral toxicities/deficiencies. Solution cultur e experiments were conducted under controlled conditions to determine the effects of Ni on influx into roots (IN) and transport from roots t o shoots (TR) of zinc (Zn), iron (Fe), copper (Cu), manganese (Mn), ca lcium (Ca), magnesium (Mg), phosphorus (P), and sulfur (S) in white cl over (Trifolium repens L.), cabbage (Brassica oleracea var. capitata L .), ryegrass (Lolium perenne L.), and maize (Zea mays L.). Nickel decr eased both IN and TR of Zn, Cu, Ca, and Mg, but only TR of Fe and Mn i n white clover. Both IN and TR of Cu, Fe, Mn, Mg, and S were markedly decreased by Ni >30 mu M in cabbage, whereas IN and TR of P increased with Ni treatment. For ryegrass, TR of Cu, Fe, Mn, Ca, and Mg was decr eased, but IN of these elements except Mg was not affected by Ni. The IN and TR of P and S were increased in ryegrass with increasing extern al Ni levels. Nickel inhibited IN of Cu, Ca, and Mg, and TR of Zn, Cu, Fe, Mn, Ca, and Mg in maize. Plant species differed in response to Ni relative to IN and TR of mineral nutrients. Plant tolerance to Ni tox icity was associated with the influence of Ni on IN and TR of Cu, Fe, and Mn in white clover and cabbage but not in maize and ryegrass.