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Young tips of a spruce tree.

Doctoral defence of Hao Yu, MSc, 9.6.2023: Responses of conifers to ozone pollution and impacts on plant-plant interactions

The doctoral dissertation in the field of Environmental Ecology will be examined at the Faculty of Science, Forestry and Technology, Kuopio Campus and online.

What is the topic of your doctoral research? Why is it important to study the topic?

In my doctoral research, I aimed to reveal the impact of ozone pollution on photosynthetic physiology, volatile emissions and plant-plant interactions in conifers. Understanding the ecophysiological and chemical-ecological responses of conifers to ozone in the light of expected increases in ozone levels in the future is of great importance. Moreover, my research evaluated the effects of biogenic secondary organic aerosols (SOA) as potential signal providers in interactions between plants. SOA is formed from the oxidation of plant volatiles in the atmosphere and their effect on ecological processes is largely unknown. The topic selected for the thesis is multidisciplinary and brings new and important information to the fields of the study.

What are the key findings or observations of your doctoral research?

In this thesis, I have demonstrated that volatile-mediated plant-plant interactions occur in conifer species. I showed that plants that received herbivore-induced plant volatile (HIPV) cues – which can be considered the scent of a plant damaged by herbivores – can prepare for future herbivore attack through modulation of responses spanning photosynthesis and chemical defense. HIPVs induced by both above- and belowground feeding have been observed to act as mediators of plant-plant interactions. From the point of view of application, my findings promote the possibility to utilize eco-friendly plant-plant interactions for pest management in boreal forests. Most interestingly, we found that SOA particles formed from oxidation of HIPVs can also function in mediating interactions between plants, with the SOA ‘inheriting’ the ecological functions of the initial volatiles. This finding adds new knowledge to the research field of plant-plant interactions. It is expected to drive more studies to further understand the ecological and evolutionary functions of plant-derived SOA.

What are the key research methods and materials used in your doctoral research?

This thesis was jointly accomplished through collaboration between the Department of Environmental and Biological Sciences and the Department of Technical Physics in the University of Eastern Finland. This thesis focused on conifer species, Scots pine and Norway spruce, and large pine weevil, and has been successfully carried out with the use of state-of-art instruments and statistical approaches. It provides a unique platform for multidisciplinary research encompassing the disciplines of plant ecophysiology, chemical ecology and atmospheric physics.

The doctoral dissertation of Hao Yu, MSc, entitled Responses of conifers to ozone pollution and impacts on plant-plant interactions  will be examined at the Faculty of Science, Forestry and Technology, Kuopio Campus. The opponent will be Professor Francesco Loreto, University of Naples Federico II, Italy,  and the custos will be Professor James Blande, University of Eastern Finland. Language of the public defence is English.

For more information, please contact: 

Hao Yu,