The role of root organic acids in the tolerance of Festuca rubra to zinc, lead and cadmium

Abstract

Festuca rubra L. plants are pseudometallophytes colonizing abandoned Pb/Zn mine areas, successfully employed in phytostabilization. To study the contribution of low-molecular weight organic acids to metal tolerance, F. rubra plants were grown for three months in hydroponics with Cd (1.8, 18 and 36 µmol L⁻¹), Pb (50, 250 and 500 µmol L⁻¹) and Zn (0.3, 3 and 6 mmol L⁻¹), separately, and in ternary combination (18 µmol L⁻¹ Cd + 250 µmol L⁻¹ Pb + 0.3 mmol L⁻¹ Zn). The roots retained most of the metals but their distribution from shoot to root was altered when the plants were treated with the ternary combination. The main organic acids in roots were citrate and malate. At the lowest concentrations, the metals caused small reductions in biomass, had no effects on photosynthetic pigments nor on malondialdehyde, but led to increases in root organic acids. At higher concentrations, phytotoxic responses were observed, associated with a decline of citrate and malate in the roots.

Keywords:

• Phytotoxicity
• cadmium
• lead
• zinc
• plant stress indicators
• citrate
• malate

Acknowledgements

The authors thank ICP-MS laboratory (SIDI – UAM) for analytical determinations. The authors are indebted to Prof Dr JM Becerril and his research team for the gift of the plants and helping advice. This paper is dedicated to the memory of Dr. Pilar Zornoza.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Spanish Ministry of Economy and Competitiveness [AGL2012-39715-C03-03] and [CTM2013-48697-C2-2-R].