Bark Photosynthesis

The research in plant physiology and anatomy of woody plants has focused mainly on the wood of stems, primary roots, and leaves, while the bark has received far less attention until now. Small pores in the outer bark, called lenticels, allow continuous gas exchange between the atmosphere and the underlying living tissues of the bark and wood. Immediately beneath the dead outer bark lies a green sleeve of living cells that surrounds the stem and contains abundant chloroplasts. The main function of this green sleeve is thought to be related to the refixation of respiratory carbon dioxide, but it may also serve other functions vital to the tree`s survival, such as supplying oxygen, maintaining water transport, defending against pathogens, and protecting against mechanical injuries. As trunks age, rhytidome formation reduces the light penetration through the outer bark, making the inner bark incapable of photosynthesis. This represents a trade-off between the protective function of the outer bark and the physiological function of the underlying living tissues. The main objective is to investigate the multi-functionality of the living green layers of the bark in terms of: carbon balance, plant hydraulics, gas exchange, light transmission, and biomechanical functions. The project aims to establish a new research discipline called "phytodermatology" that incorporates functional, structural, and physiological approaches to the study of bark in order to fill gaps in our current knowledge.