SREL Reprint #2628

Effects of PB-EDTA and EDTA on oxidative stress reactions and mineral uptake in Phaseolus vulgaris

Wouter Geebelen1,2, Jaco Vangronsveld1, Domy C. Adriano2, Lucien C. Van Poucke3, and Herman Clijsters1

1Environmental Biology, Centre for Environemental Sciences, Limburgs Universitair Centrum,
Universitaire Campus, B-3590 Diepenbeek, Belgium
2University of Georgia, Savannah River Ecology Laboratory, Aiken, SC 29802, USA
3Laboratory of Inorganic and Physical Chemistry, Centre for Environmental Sciences,
Limburgs Universitair Centrum, Universitaire Campus, B-3590 Diepenbeek, Belgium

Abstract: Sequestration of Pb by synthetic chelates has been reported to increase bioavailability, uptake, and translocation of this metal in plants. In this work the potential phytotoxic effects of Pb-EDTA were investigated in Phaseolus vulgaris L. cv. Limburgse vroege plants grown on hydroponics. Addition of 50 µM Pb-EDTA to the nutrient solution caused a significant induction of syringaldazine peroxidase (SPOD; EC 1.11.1.7) in roots and primary leaves and guaiacol peroxidase (GPOD; EC 1.11.1.7) in leaves. Addition of 100 µM Pb-EDTA further exacerbated ascorbate peroxidase (APOD; EC 1.11.1.11), GPOD, dehydroascorbate reductase (DHAR; EC 1.8.5.1), glutathione reductase (GR; EC 1.6.4.2) and malic enzyme (ME; EC 1.1.1.40) in roots and APOD and ME in primary leaves. Addition of 200 µM Pb-EDTA also induced DHAR in leaves. This induction of peroxidases (SPOD, GPOD, APOD), enzymes of the ascorbate-glutathione cycle (DHAR, GR in roots) and of an NADP+ reducing enzyme in roots and primary leaves indicates that oxidative stress has been initiated. At 200 µM Pb-EDTA, chlorophyll a and b content in leaves was significantly reduced while visible effects on root morphology and shoot length were observed, while no significant morphological effects were found in the leaves, confirming the sensitive character of the measured enzymes as plant stress indicators. Elevation of the Pb-EDTA concentration in the growth medium significantly reduced the content of Ca, Fe, Mn and Zn taken up by plants, probably due to ion leakage as a result of observed toxicity. Addition of up to 200 µM EDTA increased chelation of divalent cations in nutrient solution resulting in reduced plant uptake of Zn, Cu, Fe and Mn. This did not result in phytotoxicity.

SREL Reprint #2628

Geebelen, W., J. Vangronsveld, D. C. Adriano, L. C. Van Poucke, and H. Clijsters. 2002. Effects of Pb-EDTA and EDTA on oxidative stress reactions and mineral uptake in Phaseolus vulgaris. Physiologia Plantarum 115:377-384.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).