Environmental and Experimental Botany 44 2000 39 – 48
Growth responses to ozone in plant species from wetlands
J. Franzaring , A.E.G. Tonneijck, A.W.N. Kooijman, Th.A. Dueck
Plant Research International, P.O. Box
16
,
6700
AA Wageningen, The Netherlands Received 20 October 1999; received in revised form 9 February 2000; accepted 12 February 2000
Abstract
Ten wet grassland species were fumigated with four concentrations of ozone charcoal-filtered air, non-filtered air and non-filtered air plus 25 or 50 nl l
− 1
ozone in open-top chambers during one growing season to investigate the long-term effect of this air pollutant on various growth variables. Only Eupatorium cannabinum showed ozone-related
foliar injury, while five species reacted with significantly ozone-enhanced senescence. Premature senescence was paralleled by a significant ozone-induced reduction of green leaf area in Achillea ptarmica, E. cannabinum and
Plantago lanceolata. At the intermediate harvest performed after 28 days shoot weights were significantly decreased by ozone in A. ptarmica and increased in Molinia caerulea. At the final harvest performed at the end of the growing
season two other species, Cirsium dissectum and E. cannabinum had a significantly reduced shoot weight due to ozone. Root biomass was determined only at the intermediate harvest. The root:shoot ratio RSR was significantly reduced
in C. dissectum, while it increased in M. caerulea. Seven of the species developed flowers during the experiment. While no significant ozone effects on flowering date and flower numbers were detected, flower weights were significantly
reduced in E. cannabinum and P. lanceolata. © 2000 Elsevier Science B.V. All rights reserved.
Keywords
:
Cirsio-Molinietum; Foliar injury; Natural vegetation; Ozone sensitivity; Premature senescence www.elsevier.comlocateenvexpbot
1. Introduction
Concentrations of tropospheric ozone in rural areas are higher on average compared to urban
areas, posing a phytotoxic risk to crops and natu- ral vegetations. In Europe, critical levels for ozone
are currently being proposed within the frame- work of the UNECE to protect crops, forests
and natural vegetation against adverse effects of rising concentrations of ozone Fuhrer and
Achermann, 1999. This has resulted in broad research on the response of a significant number
of plant species from the European flora to ozone. Some short-term experiments were performed in
fumigation cabinets in the 1980s in which more than 200 European herbaceous species were ex-
posed to elevated ozone concentrations Cornelius et al., 1985; Ashmore et al., 1987. In such screen-
ing experiments, visible injury has been frequently used as a reliable response parameter. However,
chronic responses due to longer lasting episodes of elevated ozone may have greater ecological
significance to a vegetation than responses to acute exposures to ozone.
Corresponding author. E-mail address
:
j.h.franzaringplant.wag-ur.nl J. Fran- zaring.
S0098-847200 - see front matter © 2000 Elsevier Science B.V. All rights reserved. PII: S 0 0 9 8 - 8 4 7 2 0 0 0 0 0 5 2 - 6
A number of species from various European vegetation types have also been included in long-
term experiments to date. Bergmann et al. 1996, 1998 and Pleijel and Danielsson 1997 studied
the ozone sensitivity of a number of annual and biennial ruderals. Ashmore et al. 1996 concen-
trated on a range of dry calcareous grassland species while Grub et al. 1997, Bungener et al.
1999 fumigated perennial species from managed pastures. No published information so far exists
on the ozone sensitivity of species from wetlands including fen meadows and mires although rem-
nants of such ecosystems are under special protec- tion throughout Europe. Changes in hydrology
and eutrophication have already had negative ef- fects in the past decades Joyce and Wade, 1998,
but are there any effects known of the long-term impact of ozone on wetlands? The uptake of
ozone and other air pollutants is inherently cou- pled to the gas exchange of a plant Reich, 1987
and in studies on crops it has been shown that readily transpiring plants grown under moist soil
conditions are more susceptible to ozone than plants grown under a slight drought stress. It can
be hypothesised that vegetations from perma- nently wet environments are at a greater risk to
adverse ozone concentrations than plants and vegetations growing in a dry habitat. Further-
more, the importance of relative growth rates and leaf morphology in relation to the ozone sensitiv-
ity of plant species requires testing.
To study the ozone sensitivity of wetland spe- cies, an experiment was performed using common
taxa from the Dutch flora. Ten perennial herbs and grasses from extensively managed wet grass-
lands were used in a fumigation experiment with open-top chambers to investigate the ozone sensi-
tivity in terms of growth responses. The results of the experiment will be presented and discussed in
this paper.
2. Material and methods
