The survey unveiled significant insights into the evolutionary relationships between wood nano-structure and cell wall composition, revealing distinct differences between angiosperms and gymnosperms.

Researchers from Cambridge University’s botanic garden have identified a novel type of wood that defies classification as either hardwood or softwood. This discovery emerged during an evolutionary survey examining the microscopic structures of wood from 33 tree species.

The study focused on understanding how wood ultra-structure has evolved among softwoods, such as pines, and hardwoods, such as oaks and birches. Notably, the Tulip tree, related to magnolias and capable of reaching heights over 30 metres (100 feet), exhibited a unique wood structure.

This may provide insights into the tree’s rapid growth and height, particularly given its evolutionary divergence from magnolias during periods of low atmospheric CO2 levels.

This discovery opens avenues for enhancing carbon capture and storage through the cultivation of fast-growing species like the Tulip tree, often found in ornamental gardens.

Important insights

The wood samples were meticulously collected from the botanic garden, reflecting the evolutionary history of gymnosperms and angiosperms. Researchers utilised the Sainsbury Laboratory’s low-temperature scanning electron microscope (cryo-SEM) to analyse the nano-scale architecture of the wood’s secondary cell walls in their hydrated state.

Dr. Raymond Wightman, the Microscopy Core Facility Manager at the Sainsbury Laboratory, noted that their analysis included iconic trees like the Coast Redwood and the Wollemi Pine, along with ancient species such as Amborella trichopoda.

The survey unveiled significant insights into the evolutionary relationships between wood nano-structure and cell wall composition, revealing distinct differences between angiosperms and gymnosperms.

Macro-fibril structures

The study found that the two remaining species of the Liriodendron genus – Tulip tree (Liriodendron tulipifera) and Chinese Tulip tree (Liriodendron chinense) – possess macro-fibrils that are larger than those of their hardwood relatives. While typical hardwood macro-fibrils are about 15 nano-metres in diameter and softwood macro-fibrils are around 25 nano-metres, the Tulip trees feature intermediate macro-fibrils measuring approximately 20 nano-metres.

Dr. Jan Łyczakowski, the lead author of the research published in New Phytologist, stated that this intermediate structure represents a significant deviation from the typical softwood and hardwood classifications.

He explained that the Tulip trees’ macro-fibrils likely contribute to their effectiveness in carbon storage, particularly as they evolved during a period of declining atmospheric CO2 levels.

The enlarged macro-fibril structure could facilitate greater carbon capture, making Tulip trees promising candidates for carbon sequestration initiatives. Some East Asian countries are already leveraging Liriodendron plantations for this purpose.

Despite the importance of wood structure in environmental adaptation, much remains unknown about its evolution.

This study has unveiled a previously unobserved wood ultra-structure and highlighted the diversity of wood types within gymnosperms, offering crucial insights for future carbon capture efforts to combat climate change.

The architecture of wood’s secondary cell walls, which serve as significant carbon reservoirs, underscores the need for further research in this area.

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