In a recent survey of the microscopic structure of wood from iconic trees and shrubs, researchers have made a groundbreaking discovery: a completely new type of wood. This finding has the potential to revolutionize carbon sequestration in plantation forests by introducing a fast-growing tree commonly found in ornamental gardens.
The study identified Tulip Trees, which can reach heights of over 100 feet and are related to magnolias, as possessing a unique type of wood that defies classification as either hardwood or softwood.
The researchers from Jagiellonian University and the University of Cambridge used a low-temperature scanning electron microscope (cryo-SEM) to capture the nanoscale architecture of secondary cell walls (wood) in their natural hydrated state.
In their study, they discovered that the two surviving species of the ancient Liriodendron genus, specifically the Tulip Tree (Liriodendron tulipifera) and Chinese Tulip Tree (Liriodendron Chinese), possess significantly larger microfibrils compared to their hardwood relatives. Macrofibrils are long fibers aligned in layers within the secondary cell wall.
Dr. Jan Łyczakowski from Jagiellonian University, the lead author of the research published in New Phytologist, noted, “We show Liriodendrons have an intermediate macrofibril structure that is significantly different from the structure of either softwood or hardwood. Liriodendrons diverged from Magnolia Trees around 30-50 million years ago, which coincided with a rapid reduction in atmospheric CO2. This might help explain why Tulip Trees are highly effective at carbon storage.”
The team speculates that the larger macrofibrils in this “midwood” or “accumulator-wood” may be responsible for the rapid growth of Tulip Trees.
“Both Tulip Tree species are known to be exceptionally efficient at locking in carbon, and their enlarged macrofibril structure could be an adaptation to help them more readily capture and store larger quantities of carbon when the availability of atmospheric carbon was being reduced,” Łyczakowski added. “Tulip Trees may end up being useful for carbon capture plantations. Some East Asian countries are already using Liriodendron plantations to efficiently lock in carbon, and we now think this might be related to its novel wood structure.”
Liriodendron tulipifera is native to northern America, while Liriodendron chinense is native to central and southern China and Vietnam. The discovery was part of a survey of 33 tree species from the Cambridge University Botanic Garden’s Living Collections, exploring wood ultrastructure evolution across softwoods and hardwoods.
“Despite its importance, we know little about how the structure of wood evolves and adapts to the external environment. We made some key new discoveries in this survey – an entirely novel form of wood ultrastructure never observed before and a family of gymnosperms with angiosperm-like hardwood instead of the typical gymnosperm softwood,” Łyczakowski said.
“The main building blocks of wood are the secondary cell walls, and it is the architecture of these cell walls that give wood its density and strength that we rely on for construction. Secondary cell walls are also the largest repository of carbon in the biosphere, which makes it even more important to understand their diversity to further our carbon capture programs to help mitigate climate change.”
“We analysed some of the world’s most iconic trees, like the giant sequoia and Wollemi pine, and so-called “living fossils” such as Amborella trichopoda, which is the sole surviving species of a family of plants that was the earliest still existing group to evolve separately from all other flowering plants,” said Dr Raymond Wightman, Microscopy Core Facility Manager at the Sainsbury Laboratory Cambridge University.
“Our survey data has given us new insights into the evolutionary relationships between wood nanostructure and the cell wall composition, which differs across the lineages of angiosperm and gymnosperm plants. Angiosperm cell walls possess characteristic narrower elementary units, called macrofibrils, compared to gymnosperms and this small macrofibril emerged after divergence from the Amborella trichopoda ancestor.”
Lyczakowski and Wightman’s analysis of the cell wall macrofibrils in Gnetum gnemon and Gnetum edule, both members of the Gnetophytes family, revealed a secondary cell wall ultrastructure resembling that of hardwood cell walls in angiosperms. This discovery demonstrates a remarkable case of convergent evolution, where Gnetophytes independently developed a hardwood-type structure typically associated with angiosperms. It’s truly fascinating how these plants have adapted and evolved. The research was conducted during the exceptionally warm summer of 2022 in the UK.
Journal reference:
- Jan J. Lyczakowski, Raymond Wightman. Convergent and adaptive evolution drove change of secondary cell wall ultrastructure in extant lineages of seed plants. New Phytologist, 2024; DOI: 10.1111/nph.19983