The doctoral dissertation in the field of Biology will be examined at the Faculty of Science, Forestry and Technology, Joensuu campus, and online.
What is the topic of your doctoral research? Why is it important to study the topic?
Plant phenotyping is a process of measuring and analyzing observable plant characteristics affected by genetics, environment, and their interactions. This thesis provides methodological insights into sensor and image-based phenotyping for characterization of forest tree responses to environmental and stress conditions in ecophysiological studies.
Changing environmental conditions due to climate change could have damaging effects on seedling establishment and growth of forests. The preservation and improvement of forest resources have thus become increasingly vital to ensuring a sustainable future for our environment, biodiversity, and economy. Advanced phenotyping methods are needed to support the selection of plants with adaptive potential to changing environments.
What are the key findings or observations of your doctoral research?
The phenotyping methods used in this work, chlorophyll fluorescence induction and spectral reflectance, can both be used to support the selection of plants with desired properties. The results show how environmental factors and tree origin influence diurnal and within-tree variability of chlorophyll fluorescence and variation of foliar spectral traits, enabling improved assessment of plant physiological responses and performance.
A time-adjusted JIP test method is proposed as an alternative approach for evaluating rapid chlorophyll fluorescence transient kinetics, particularly under varying light conditions during the day. Differences between Northern and Southern birch origins were only shown under low light in the morning and in the evening. Regarding day-to-day variation, tree origin differences were shown to be relatively stable but may be influenced by physiological alterations in preparation for future changes in environmental conditions.
The two compared non-imaging spectral reflectance acquisition methods proved effective for detecting differences among Scots pine seedlings from three populations. Although one of the methods was more sensitive to ambient illumination, it incorporated seedling crown structural information and achieved higher classification accuracy for tree origins with machine learning algorithms.
Hyperspectral imaging of drought-exposed European aspen saplings showed uninformative variability in spectral reflectance caused by differences in plant growth and architecture during the experiment. This and other potential challenges in using hyperspectral imaging in phenotyping experiments were addressed. By recording spectral information in the visible and near-infrared range, the approach was effective in characterizing optical leaf traits associated with drought and recovery responses in European aspen accessions.
How can the results of your doctoral research be utilised in practice?
The results of this thesis can improve the implementation of optical phenotyping methods used in the assessment of tree responses under varying environmental and stress conditions, for example, in tree nurseries. These phenotyping methods are rapid, non-invasive, and quantitative, and can be used for the selection of elite individuals and to evaluate their response to increasing drought spells, pathogen and insect invasions that will impact timber yield, forest health, and productivity.
What are the key research methods and materials used in your doctoral research?
In this study, rapid chlorophyll fluorescence induction and spectral reflectance with point measurements and imaging were used to assess trait differences of seedlings and cloned saplings of three forest tree species. Finnish silver birch, Czech European aspen and Scots pine origins were used in studies focusing on methodological aspects and intraspecific variation.
This research was conducted utilizing the instrumentation and facilities of the National Plant Phenotyping Infrastructure (NaPPI) at the 91 and University of Helsinki, as well as Czech University of Life Sciences, Prague, and was part of the Academy of Finland flagship programme Photonics Research and Innovation (PREIN).
The doctoral dissertation of Olusegun Olaitan Akinyemi, MSc, entitled Phenotyping intraspecific trait variation of forest trees by chlorophyll fluorescence and spectral reflectance will be examined at the Faculty of Science, Forestry and Technology, Joensuu Campus. The opponent will be Professor Albert Porcar-Castell, University of Helsinki, and the custos will be Research manager Markku Keinänen, 91. Language of the public defence is English.
For further information, please contact:
Olusegun Olaitan Akinyemi, olusegak@uef.fi
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