Evolutionary and functional traits of parenchyma in the hydraulic architecture plants
Plant Physiology
Final Report Abstract
This project aimed to better understand the structure-functional role of living cells (parenchyma) in wood, which is far from a biologically “dead” tissue. It was well known that conifers and flowering plants show clear differences in the amount of parenchyma, but exact quantification had never been explored on a global scale. By combining literature data with novel datasets, we were able to present a general framework to discuss the 29-fold variation in the amount and arrangement of parenchyma cells in wood. From an ecological point of view, we illustrated that temperature is the main determinant of parenchyma cells that have an axial orientation. The amount of parenchyma was also found to be strongly depended on the growth form, with climbing plants and succulents in tropical environments showing the highest amounts of parenchyma. Despite various similarities between the two main types of parenchyma (i.e., axial and ray parenchyma), our ecological and phylogenetic analyses show that both types can be uncoupled from each other and may have independent functions. Probably the most exciting discovery in this project is that parenchyma cells produce insoluble lipids that are secreted into the xylem sap that is typically transported under negative pressure. In fact, we hypothesise that these lipid surfactants are a requirement for water transport under negative pressure by coating hydrophobic surfaces and nanobubbles, thereby keeping the latter below the critical size at which bubbles would expand to cause failure of the transport system. Therefore, the unexpected finding of lipids in xylem sap may shed new light on the long-standing debate about how plants transport water under negative pressure. This finding has the potential for biomimetic applications and will be further explored in follow-up projects. Functionally, we were able to confirm that the amount of parenchyma in wood is correlated with the maximum storage capacity of non-structural carbohydrates of temperate trees. We also provided evidence that the amount of parenchyma is important for the storage of water that can be released during periods of drought stress, although this correlation is complicated by water stored in other cells types such as fibres. The importance in living cells for defence against various pathogens (e.g., fungi) was explored by revisiting a compartmentalisation model (CODIT), and by reconstructing three-dimensional patterns of how parenchyma cells are spatially arranged, interconnected, and associated with the hydraulic transport system. The PI contributed to a short documentary at a synchrotron facility in Paris, which is available online and used for educational purposes. This video illustrates the importance of basic research questions such as the resistance of water transporting cells in plants to hydraulic dysfunction and what we can learn by applying novel techniques such as X-ray computed tomography (microCT): http://www.synchrotronsoleil.fr/Presse/Videos/StressHydrique. A short note about this parenchyma project in relation to large-scale tree mortality was published on 9 August 2016 in the Südwest Presse: „Waldsterben in Zeiten des Klimawandels“.
Publications
- (2015) A global analysis of parenchyma tissue fractions in secondary xylem of seed plants. First International Xylem meeting, Bordeaux, France, 7-9 September 2015
Morris H, Plavcová L, Jansen S.
(See online at https://doi.org/10.1111/nph.13737) - (2015) The role of xylem parenchyma in the storage and utilization of non-structural carbohydrates. In: Functional and Ecological Xylem Anatomy, ed. U. Hacke, Springer-Verlag: 209-234
Plavcová L., Jansen S.
(See online at https://doi.org/10.1007/978-3-319-15783-2_8) - (2016) A global analysis of parenchyma tissue fractions in secondary xylem of seed plants. New Phytologist 209: 1553-1565
Morris H., Plavcová L., Cvecko P., Fichtler E., Gillingham M.A.F., Martínez-Cabrera H.I., McGlynn D.J., Wheeler E., Zheng J., Ziemińska K., Jansen S.
(See online at https://doi.org/10.1111/nph.13737) - (2016) Linking xylem water storage with anatomical parameters in five temperate tree species. Tree Physiology 36: 756-769
Jupa R., Plavcová L., Gloser V., Jansen S.
(See online at https://doi.org/10.1093/treephys/tpw020) - (2016) Secondary xylem parenchyma - from classical terminology to functional traits. International Association of Wood Anatomists Journal 37: 1-15
Morris H., Jansen S.
(See online at https://doi.org/10.1163/22941932-20160117) - (2016) The amount of parenchyma and living fibers affects storage of non-structural carbohydrates in young stems and roots of temperate trees. American Journal of Botany: 103: 603-612
Plavcová L., Hoch G., Morris H., Ghiasi S., Jansen S.
(See online at https://doi.org/10.3732/ajb.1500489) - (2016) The chemical identity of intervessel pit membranes in Acer challenges hydrogel control of xylem hydraulic conductivity. AoB Plants. 8: plw052
Klepsch M., Schmitt M., Knox P., Jansen S.
(See online at https://dx.doi.org/10.1093/aobpla/plw052) - (2016) The parenchyma of secondary xylem and its critical role in tree defense against fungal decay in relation to the CODIT model. Frontiers in Plant Science 7: article 1665
Morris H., Brodersen C., Schwarze F.M.W.R., Jansen S.
(See online at https://doi.org/10.3389/fpls.2016.01665) - (2016) The structure and multiple functions of vessel-associated cells in xylem. Annual meeting of the Botanical Society of America, Savannah, USA, July 30 - August 3, 2016
Morris H., Schiele S., Klepsch M., Schenk H.J., Jansen S.
- (2017). Xylem surfactants introduce a new element to the cohesion-tension theory. Plant Physiology 173: 1177-1196
Schenk H.J., Espino S., Romo D.M., Nima N., Do A.Y.T., Michaud J.M. Papahadjopoulos-Sternberg B., Yang J., Zuo Y.Y., Steppe K., Jansen S.
(See online at https://doi.org/10.1104/pp.16.01039)
