Yusuph Olawale Abiola investigated the effects of climate change on plants' stress tolerance in his doctoral thesis

The thesis was supervised by Professor Ülo Niinemets of the Estonian University of Life Sciences, and the opponent was Professor Francesco Loreto (University of Naples Federico II, Italy).

Climate change affects plant growth and metabolism

The main drivers of climate change, including rising temperatures and reduced water availability, decrease photosynthesis and crop yield potential in agricultural plants. Although increasing atmospheric carbon dioxide (CO₂) concentrations accelerate global warming, they also directly affect plant metabolism. Elevated CO₂ levels can stimulate photosynthesis only when sufficient nutrients are available. However, accelerated plant growth often limits the availability of nitrogen and phosphorus, which may ultimately lead to a decline in photosynthetic performance.

The doctoral thesis examined the effects of elevated CO₂ concentration and heat stress on leaf structure, photosynthesis, and volatile organic compound (VOC) emissions in plants at different developmental stages. Particular attention was paid to how plant responses vary among species and with leaf age.

Plant species respond differently to changing conditions

The results revealed strong species-specific responses. For example, elevated CO₂ concentration increased leaf area and dry mass in avocado (Persea americana), whereas these traits decreased in soursop (Annona muricata). Nutrient concentrations and photosynthetic capacity also responded differently among species.

The findings confirmed that plant responses to changing environmental conditions depend largely on species-specific growth strategies, leaf structural characteristics, and resource allocation patterns. Consequently, the impacts of climate change cannot be predicted uniformly across all plant species.

Heat stress impairs photosynthesis

Heat stress is one of the most rapidly increasing abiotic stress factors, affecting processes ranging from photosynthesis to hormonal regulation. The results of the thesis showed that heat stress reduced photosynthesis primarily through non-stomatal mechanisms by damaging the biochemical processes underlying photosynthesis.

The study also investigated emissions of volatile organic compounds, which constitute an important component of plant stress responses. Heat stress increased the emission of compounds associated with cell membrane damage and the activation of plant defence mechanisms. In addition, the research demonstrated that prior exposure to moderate stress, known as priming, improved heat tolerance and accelerated post-stress recovery in oregano (Origanum vulgare).

The doctoral thesis demonstrates that plant responses to elevated CO₂ concentrations and heat stress depend both on species-specific characteristics and on leaf developmental stage. The results contribute to a better understanding of plant adaptation to future climatic conditions and support efforts to predict changes in agricultural systems and natural ecosystems.

The doctoral thesis is available in the Estonian University of Life Sciences digital repository, EMÜ DSpacelink opens in new page.