Critical levels for visible ozone injury to Prunus serotina in south Switzerland

Rationale

Leaves of Prunus serotina in souh Switzerland

Typical upper surface stippling on Prunus serotina leaf

Map of ozone damage in Tessin. Klick on image to enlarge.

Symptoms typical of ozone injury were first identified on Prunus serotina individuals growing in Ticino in 1993. Subsequent surveys revealed that the symptoms occurred at many sites in southern Ticino (Fig. 1). Preliminary experimental studies undertaken at the Department of Plant Pathology of the Pennsylvania State University using seed collected from symptomatic trees indicated that it was extremely likely that the symptoms being seen in southern Ticino were the result of ozone injury.

Project aims

The aims of this project were:

1. to confirm that foliar injury seen on Prunus serotina in Ticino is caused by ozone
2. to determine the ozone concentrations that induce the injury.

Methods

In the first part of the study, seeds from 3 Prunus serotina (2 highly symptomatic and 1 asymptomatic) from near Magliaso, TI were used. Seeds were germinated in spring 1994 and emerging seedlings were fumigated with ozone at four exposures (30, 60, 90, and 120 ppb ozone) for 7 h/da , 5 da/wk, for 5 wks within the Continuously Stirred Tank Reactor Chamber system at the Pennsylvania State University; two replications per treatment. Typical upper surface stippling developed on the seedlings derived from the 2 field symptomatic trees in TI but none developed on the foliage of the seedlings derived from the tolerant parent. Symptoms developed on the sensitive seedlings first at the highest exposures, but symptoms also were clearly evident on the seedlings exposed at 90 and 60ppb ozone at the midpoint of the exposure duration; no symptoms developed on any of the seedlings at the 30ppb ozone exposure.

Seed were collected from 10 symptomatic and non-symptomatic trees growing in Ticino. Following germination, the seedlings were planted directly into the ground in open-top chambers or open plots. For the experiment, three different treatments were replicated twice: chambers with charcoal-filtered air (ca. 40% ambient ozone), chambers with ambient air (ca. 95% ambient ozone) and open plots. The experiment was conducted for two consecutive years. Symptoms developed at ozone A0T40 exposures of 2 ppmh.

Work plan

This project is now completed. The results are available in the publications listed below.

Publications

• Innes J.L., Skelly J., Landolt W., Hug C., Snyder K.R., Savage J.E., 1996. Development of visible injury on the leaves of Prunus serotina in Ticino, southern Switzerland, as a result of ozone exposure. Preliminary results. In: M. Knoflacher, J. Schneider, G. Soja (eds), Exceedance of critical loads and levels. Report of a workshop held in Vienna, Austria under the Convention on Long Range Transboundary Air Pollution, 22-24 November 1995. Conference Papers no. 15. Vienna, Bundesministerium für Umwelt, Jugend und Familie, pp. 146-154.
  
• Matyssek R., Havranek W.M., Innes J.L., Wieser G., 1997. Ozone and the forests in Austria and Swizterland. In: H. Sandermann, R.L. Heath, A. Wellburn (eds), Forest decline and ozone: a comparison of controlled chamber and field experiments. Springer Verlag, pp. 95-134.
• Skelly J., Innes J.L., Snyder K.R., Savage J.E., Hug C., Landolt W., Bleuler P., (in press). Investigations of ozone induced injury in forests of southern Switzerland: Field surveys and open-top chamber experiments. Chemosphere.

Participants

• John Innes (project leader)
• Peter Bleuler
• Christian Hug
• Werner Landolt
• Peter Lawrenz
• Giorgio Moretti (Forest Service, Tessin)
• Jim Savage (PennState University)
• John Skelly (PennState University)
• Ken Snyder (PennState University)
• G. Tettamanti (Forest Service, Tessin)

Contact

• Marcus Schaub