Plasticity and light sensitivity of leaf hydraulic conductance to fast changes in irradiance in common hazel (Corylus avellana L.).

Forest understory species have to acclimatize to highly heterogeneous light conditions inside forest canopies in order to utilize available resources efficiently. Light sensitivity and response speed of hydraulic conductance (K) of common hazel (Corylus avellana L.) to fast changes in irradiance was studied in leaves from three different growth light conditions-sun-exposed, moderate shade, and deep shade. The K of sun-exposed leaves was approximately 3-fold higher when compared to deep-shade leaves, indicating a strong dependence of leaf hydraulic capacity on light conditions. The K of sun-exposed leaves increased by a factor of nearly four from minimal values recorded in darkness to maximal values in high light compared to deep-shade leaves. Reaction speed of K to reach maximum values in response to light was nearly five times higher for sun-exposed vs deep-shade leaves. Plasticity indices of K for sun-exposed and deep-shade leaves were 0.44 and 0.27, respectively. Higher light sensitivity enables a faster and more plastic response of K to variable light conditions in sun leaves and enhances the ability of plants to maximize resource utilization under more beneficial environmental conditions.