Physiological effects of copper on iron acquisition processes in Plantago

Abstract

(This paper is dedicated to the memory of Professor Horst Marschner) SUMMARY In Plantago lanceolata L. the effect of Cu(II) additions to the nutrient solution on root-associated Fe(III) reductase was studied in a factorial design with different Cu(II) and Fe(III) concentrations. Iron starvation resulted in approx. an eightfold increase in root Fe reduction at the level of intact plants and twofold enhancement in the specific activity of both NADH-linked FeEDTA reductase and H^-ATPase in isolated root plasma membrane vesicles. In plants exposed to low (0-3-0-7 /iM) Cu and suboptimal Fe levels, reduction activity at the root surface was further increased and associated with more severe interveinal chlorosis than plants grown in Cufree medium. In Fe-sufficient plants, withholding Cu over a prolonged period slightly enhanced the reduction activity.Addition of high (5 fiM) Cu concentrations to Fe-free medium inhibited the induction of the physiological responses by Fe-deficiency stress. In plants without Fe supply but with adequate Cu supply, short-term application of 5 /iM CuSO^ completely inhibited the reduction activity. Neither incubation of the plasma membrane vesicles before measurement nor incubation of intact plants with Cu before isolation caused a significant decrease in reductase activity. The results are interpreted as indicating different mechanisms underlying Cu-induced alterations in iron nutrition.

Optimal copper supply is required for normal plant iron deficiency responses

“…The third phase of the curve indicates Cu toxicity, which abolished ferricchelate reductase activity. Similar inhibition of ferric-chelate reductase activity by high Cu has been observed in cucumber 34 and Plantago lanceolata, 30 but high Cu did not inhibit ferric-chelate reductase protein activity in Plantago membrane isolates, which suggested that Cu blocked expression rather than function of the ferric reductase.…”

“…A similar inhibition for whole root ferric-chelate reductase activity by low Cu was observed for Plantago lanceolata. 30 In pumpkin, and in cucumber supplied with 0.5 µM Fe, 0 Cu was optimal. As Cu was increased above optimal concentrations, lower ferric-chelate reductase activity occurred.…”

Crescimento e nutrição mineral de Eucalyptus maculata e Eucalyptus urophylla em solução nutritiva com concentração crescente de cobre

“…Portanto, apesar de os teores de Fe nas raízes e na parte aérea terem sido elevados pelo excesso de Cu em solução, esse exerceu alta interferência na translocação do Fe, podendo ser uma das possíveis causas da toxidez do Cu para o eucalipto. O efeito fitotóxico do Cu sobre a translocação de Fe também foi observado em espécies de Plantago em estudo realizado por Schmidt et al (1997).…”

Sensitivity to and requirement for iron in Plantago species

“…Seedlings were grown hydroponically in a climatecontrolled glasshouse as described in Schmidt et al (1997). Seeds were germinated in quartz sand moistened with tap water.…”