Global researchers have discovered a new type of wood—neither hardwood nor softwood—with major implications for the future of carbon forestry. Wood Central understands that the discovery opens new opportunities to improve carbon sequestration plantation forests by planting fast-growing trees commonly seen in ornamental gardens.
As reported by US-based Phys.Org, it found that Tulip Trees, which are related to magnolias and can grow well over 100 feet tall, have a unique type of wood that does not fit into the hardwood or softwood categories.
Scientists from Jagiellonian University in Poland and the University of Cambridge in the United Kingdom used a low-temperature scanning electron microscope (or cryo-SEM) to image the nanoscale architecture of secondary cell walls (or wood) in their native hydrated state.
It found that two surviving species of the ancient Liriodendron genus, the Tulip Tree (Liriodendron tulipifera) and Chinese Tulip Tree (Liriodendron chinense), both have larger microfibrils than their hardwood relatives.
According to lead author Jan Łyczakowski from Jagiellonian University, “Liriodendrons have an intermediate microfibril structure significantly different from the structure of either softwood or hardwood,” adding that “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.”
Dr Łyczakowski said the larger microfibrils within this “midwood” or “accumulator-wood” are behind the Tulip Trees’ rapid growth: “Tulip Tree species are known to be exceptionally efficient at locking in carbon, and their enlarged microfibril structure could be an adaptation to help them more readily capture and store larger quantities of carbon,” than hardwood and softwoods.
“Tulip Trees may end up being useful for carbon capture plantations. Some East Asian countries are already using Liriodendron plantations to lock in carbon efficiently, and we now think this might be related to its novel wood structure,” Dr Łyczakowski said, adding that Liriodendron tulipifera is native to northern America and Liriodendron chinense is a native species of central and southern China and Vietnam.
The discovery was made as part of a survey of 33 tree species from the Cambridge University Botanic Garden’s Living Collections, exploring how wood ultrastructure evolved across softwoods (including pines and conifers) and hardwoods (including oak, ash, birch, and eucalypts).
“Despite its importance, we know little about how wood’s structure evolves and adapts to the external environment,” Dr Łyczakowski said: “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.”
“The main building blocks of wood are the secondary cell walls, and it is the architecture of these cell walls that gives wood its density and strength, which 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.”
Wood ultrastructure.
Wood ultrastructure refers to the detailed microscopic architecture of wood, encompassing the arrangement and organisation of its material components. This survey of timber using a cryo-scanning electron microscope focused on:
- The secondary cell wall is composed of cellulose plus other complex sugars and is impregnated with lignin to make the whole structure rigid. These components comprise the microfibril, forming long, aligned fibres arranged in distinct layers within the secondary cell wall.
- The microfibril: This is currently the smallest structure we can measure using the cryoSEM. It is 10–40 nanometers thick and comprises cellulose microfibrils (3–4 nanometers) and other components.
Wood Central understands that studying the wood ultrastructure is crucial for various applications, including wood processing, material science, and understanding trees’ ecological and evolutionary aspects. Understanding the biology behind tree growth and wood deposition is also valuable information when calculating carbon capture.
The Living Collections of the Cambridge University Botanic Garden.
Wood samples were collected from trees in the Cambridge University Botanic Garden, curated by Margeaux Apple, the Garden’s Collections Coordinator.
According to Dr Raymond Wightman, the Microscopy Core Facility Manager at Cambridge University Sainsbury Laboratory: “We analysed some of the world’s most iconic trees like the giant sequoia, 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.”
“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 microfibrils, compared to gymnosperms, and this small microfibril emerged after divergence from the Amborella trichopoda ancestor,” Dr Wightman said.
Dr Lyczakowski and Dr Wightman then analysed the cell wall microfibrils of two gymnosperm plants in the Gnetophytes family—Gnetum gnemon and Gnetum edule—and confirmed both have a secondary cell wall ultrastructure synonymous with the hardwood cell wall structures of angiosperms.
The survey was undertaken in 2022 while the UK was experiencing its fourth-hottest summer ever recorded: “We think this could be the largest survey of woody plants ever done using a cryo-electron microscope,” according to Dr Wightman.
“It was only possible to do such a large survey of fresh hydrated wood because the Sainsbury Lab is located on the grounds of the Cambridge University Botanic Garden. We collected all the samples during the summer of 2022—collecting in the early morning, freezing them in ultra-cold slush nitrogen, and imaging them through to midnight.”
“This research illustrates botanic gardens’ continued value and impact in contributing to modern-day research. This study would not have been possible without such a diverse selection of plants represented through evolutionary time, all growing together in the same place in the Cambridge University Botanic Garden’s Collections.”
Please Note: The National Science Centre Poland and The Gatsby Charitable Foundation funded this research.
Reference: Lyczakowski, J L and Wightman, R. “Convergent and adaptive evolution drove the change of secondary cell wall ultrastructure in extant lineages of seed plants.” July 2024, New Phytologist. DOI: 10.1111/nph.19983
