Ellen Phiddian
Cosmos science journalist
UK and Polish scientists have identified a new microscopic wood structure which fits into neither the hardwood nor softwood category.
The wood, which belongs to trees in the Liriodendron genus, could be a particularly powerful absorber of carbon dioxide.
The study is published in New Phytologist.
There are 2 living Liriodendron species: the tulip tree (Liriodendron tulipifera), native to North America, and Chinese tulip tree (Liriodendron chinense), native to southern China and Vietnam. Other types of tulip tree, like the African tulip tree, are from unrelated families.
“We show Liriodendrons have an intermediate macrofibril structure that is significantly different from the structure of either softwood or hardwood,” says lead author Dr Jan Łyczakowski, a researcher at Jagiellonian University, Poland.
“Liriodendrons diverged from magnolia trees about 30–50 million years ago, coinciding with a rapid reduction in atmospheric CO2. This might help explain why tulip trees are highly effective at carbon storage.”
The researchers used a scanning electron microscope to examine wood in 33 different tree species, all from the Cambridge University Botanic Garden’s living collection.
“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,” says study co-author Dr Raymond Wightman, microscopy core facility manager at Cambridge.
“Despite its importance, we know little about how the structure of wood evolves and adapts to the external environment,” says Łyczakowski.
“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 researchers looked at the “ultrastructure” of wood: the way its material components are arranged at a microscopic level. They investigated a structure inside the wood called the secondary cell wall, and a collection of long fibres called the microfibril, which is 10–40 nanometres thick.
“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,” explains Łyczakowski.
“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 programmes to help mitigate climate change.”
The tulip trees’ wood differed from both the ultrastructures of hardwood and softwood. Their wood had much larger macrofibrils than hardwood.
“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,” says Łyczakowski.
“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.”
