Heavy metal phytotoxicity: the effects of lead on the common reed, Phragmites australis (Cav.) Trin. ex Steud.

Constructed wetlands are increasingly being used as viable biofiltration systems, effectively removing heavy metals such as lead (Pb) from contaminated wastewaters. This study examined the effects of Pb on the life cycle of Phragmites australis (Cav.) Trin. ex Steud (common reed) as increased plant productivity is thought to be integral to the metal removal process. Hydroponic gravel-based mesocosms planted with vegetative reed propagules were regularly dosed with 50 μM Pb at pH 4 during 1996-7. Sequential plant harvesting over two growing seasons showed that increased exposure to biologically-available Pb caused a reduction in the dimensions and biomass of individual plant organs; a shift in some morphological traits; and altered the composition and structure of the aerial standing crop. Significantly, the formation of new horizontal rhizomes was inhibited and this caused the decline of the dosed reed stand. This effect was promoted through various feedback mechanisms involving the number and size of apical and axillary buds, the density of shoot tillering, and the proportions and characteristics of the adult terminal and lateral daughter shoots. These plant growth features could be used as possible biological markers, indicating the growth status of reeds growing in both natural and constructed wetlands. Chemical analysis found that after two years ' Pb exposure the roots contained the highest concentrations of Pb (9.lμmole/g dry weight) with reduced metal accumulation occurring in the rhizomes and least in the aerial shoots. Other experiments testing the effects of Pb on the initial seedling growth of different reed populations showed that although increased concentrations of Pb (up to 50 μMat pH 4) did not affect seed germination, significant differences were found between the growth of the seminal root of the various populations when exposed to 5 μM Pb over 6 days. These preliminary findings demonstrate that there may be potential for ecotypic variation within P. australis.

Grantor dc:publisher

Oxford Brookes University

Author dc:creator

• Abbott, Sarah L.

Contributors dc:contributor

• Miller, Anne
• Hodson, Martin

Statement dc:rights

• All rights reserved

Language dc:language

en

DOI dc:identifier

https://doi.org/10.24384/tmgm-5c09

OAI identifier oai:identifier

tle:71689689-e1f0-4f1e-b981-71d641949403:d6bd9758-527a-46cd-bfe2-c433766e8fca:1