Research Fellow, Department of Botany, Institute of Ecology and Earth Sciences, University of Tartu, Estonia

Biograph
Dr. Eele Õunapuu-Pikas was granted a PhD degree in the field of plant ecology and ecophysiology at the University of Tartu, Estonia, in 2014. Her doctoral thesis addressed the ecophysiological consequences of spatial and temporal variability of leaf hydraulic conductance in woody plants. Currently, she is working as a research fellow at the Department of Botany, Institute of Ecology and Earth Sciences, University of Tartu. Her major is Plant Science and Climate Change with specific emphasis on plant ecophysiology and water relations. She belongs to a research group investigating forest ecosystem acclimation to increasing atmospheric humidity and interacting environmental drivers. In addition, she has expertise in other fields of plant ecology, for example experimental work with vesicular-arbuscular mycorrhiza and using the method of fluctuating asymmetry in assessment of tree vitality in relation to environmental stress factors.

Speech Title: Plasticity and light sensitivity of leaf hydraulic conductance: a study in common hazel

Abstract: Forest understorey species must acclimatize to highly heterogeneous light conditions inside forest canopies to efficiently utilize available resources. Light is one of the primary environmental drivers controlling hydraulic properties of plants. The efficiency of water transfer through leaf tissues is quantified by leaf hydraulic conductance (KL). As KL is strongly correlated with maximum stomatal conductance and photosynthetic capacity, it has a profound effect on gas exchange and biomass production and ultimately on plant performance and fitness. We studied light sensitivity and response speed of KL of common hazel (Corylus avellana L.) to fast changes in irradiance in leaves from three different growth light conditions – sun-exposed, moderate shade and deep shade. KL of sun-exposed leaves was approximately 3-fold higher compared to deep-shade leaves, indicating a strong dependence of leaf hydraulic capacity on light conditions. KL of sun leaves increased nearly by a factor of 4 more from minimal values recorded in darkness to maximal values in high light compared to deep-shade leaves. Reaction speed of KL to reach maximal values in response to turning on light was nearly five times higher for sun-exposed vs deep-shade leaves. Plasticity index of KL for sun-exposed and deep-shade leaves was 0.44 and 0.27, respectively. Our results provide evidence for high light sensitivity and hydraulic plasticity in C. avellana varying between leaf types. Higher light sensitivity enables a faster and more plastic response of KL to variable light conditions in sun leaves and enhances plant ability to maximize resource utilization under more beneficial environmental conditions and ultimately supports higher competitive ability and survival in contrasting environments. Yet, information about the plasticity of leaf hydraulic traits is still scarce compared to the plasticity of morphological, anatomical and several other physiological traits. Further testing of hydraulic plasticity of leaves with respect to diverse environmental factors is needed with a wider range of species differing in their ecology to make generalized conclusions.