Acute and chronic ozone exposure temporarily affects seed germination in alpine plants

Abstract

This study was the first to investigate the direct effects of anomalous concentrations of ozone mediated by summer heat waves on seed germination in alpine plants. During germination, the seeds were exposed to three peaks of O₃ concentration (125 ppb for 5 and 10 days; 185 ppb for 5 days), derived from measurements taken close to the species growing site. High O₃ concentration delayed the first germination time, increased the mean germination time, and reduced the germination percentage during and immediately after the treatment, but, in most cases, effects were weak and had almost vanished three weeks after the treatments. In few cases, chronic exposure to O₃ (125 for 10 days’ treatment) enhanced seed germination compared to the control, suggesting that ozone may induce antioxidant and DNA-repair mechanisms or dormancy-breaking effects in hydrated seeds. Although seed mortality increased during O₃ treatments in four species, the effect of O₃ on seed germination is mostly limited to the period of exposure, indicating that it is unlikely to produce permanent negative effects on seeds, during the germination phase. Our results show that the direct effect of O₃ on seeds of alpine plants may have minor impacts on plant reproductive performance during seed germination.

Keywords:

• Climate change
• electronic paramagnetic resonance
• extreme events
• heat waves
• pollution

Acknowledgments

Authors are grateful to Prof Alma Balestrazzi (University of Pavia) for her suggestions. This study was supported by MIUR and CNR (Project of National Interest NEXTDATA and SHARE; Stations at High Altitude for Research on the Environment) and by NASSTEC (The NAtive Seed Science, TEchnology and Conservation – EU- FP7 Programme, www.nasstec.eu).