Journal Article

Effects of oil on internal gas transport, radial oxygen loss, gas films and bud growth in <i>Phragmites australis</i>

Jean Armstrong, Rory Keep and William Armstrong

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 103, issue 2, pages 333-340
Published in print January 2009 | ISSN: 0305-7364
Published online November 2008 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcn213
Effects of oil on internal gas transport, radial oxygen loss, gas films and bud growth in Phragmites australis

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Background and Aims

Oil pollution of wetlands is a world-wide problem but, to date, research has concentrated on its influences on salt marsh rather than freshwater plant communities. The effects of water-borne light oils (liquid paraffin and diesel) were investigated on the fresh/brackish wetland species Phragmites australis in terms of routes of oil infiltration, internal gas transport, radial O2 loss (ROL), underwater gas films and bud growth.

Methods

Pressure flow resistances of pith cavities of nodes and aerenchyma of leaf sheaths, with or without previous exposure to oil, were recorded from flow rates under applied pressure. Convective flows were measured from living excised culms with oiled and non-oiled nodes and leaf sheaths. The effect of oil around culm basal nodes on ROL from rhizome and root apices was measured polarographically. Surface gas films on submerged shoots with and without oil treatment were recorded photographically. Growth and emergence of buds through water with and without an oil film were measured.

Key Results

Internodes are virtually impermeable, but nodes of senesced and living culms are permeable to oils which can block pith cavity diaphragms, preventing flows at applied pressures of 1 kPa, natural convective transport to the rhizome, and greatly decreasing ROL to phyllospheres and rhizospheres. Oil infiltrating or covering living leaf sheaths prevents humidity-induced convection. Oil displaces surface gas films from laminae and leaf sheaths. Buds emerge only a few centimetres through oil and die.

Conclusions

Oil infiltrates the gas space system via nodal and leaf sheath stomata, reducing O2 diffusion and convective flows into the rhizome system and decreasing oxygenation of phyllospheres and rhizospheres; underwater gas exchange via gas films will be impeded. Plants can be weakened by oil-induced failure of emerging buds. Plants will be most at risk during the growing season.

Keywords: Phragmites australis; oil pollution; convective flow; pressure flow resistance; phyllosphere oxygenation; rhizosphere oxygenation; underwater gas films; bud emergence; stomata; pith cavity diaphragms; leaf sheath aerenchyma; rhizome aeration

Journal Article.  5248 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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