Bark Takes A Little Light Relief

Without its sturdy trunk, a tree would cease to exist. Though it may take on a variety of forms, a trunk serves a crucial role in holding up the leaves and connecting them to the roots. Despite this, trees possess a peculiar secret hidden within their trunks.

Upon peeling back the outer bark, green tissues can be found lining the wood’s surface. These cells contain chloroplasts, the energy-producing organelles involved in photosynthesis. Although hidden from sight, these green cells utilize light to convert carbon dioxide and water into sugar, much like leaves in heavily shaded areas, albeit less efficiently.

Initially, this phenomenon may seem absurd. How could light possibly reach the chloroplasts confined beneath the bark? Recent measurements have revealed that this is remarkably simple. Light creeps through cracks in the bark, regardless of whether it is creased or smooth. Bark in certain trees tears itself apart potentially to allow light in, perhaps explaining why the inside of a sycamore’s bark reveals a mosaic of multicoloured tissues. Additionally, the bark is pitted with minuscule pores, allowing gases and small chunks of light to pass through.

Remarkably, when the bark is drenched in water, even more light enters, causing certain tree trunks to alter colour. More astonishingly, light can penetrate deep into the wood in some tree trunks. Although it may appear lifeless, wood is actually infused with a living network of veins that sprout and divide to create new wood cells, broadening and raising twigs and branches.

Some of these living cells also conduct photosynthesis, yet scientists struggle to comprehend how light reaches so far inside the trunk. Trunks apparently strive to photosynthesize, but the why remains a mystery. One theory is that doing so aerates the wood. Like animals, all plants require oxygen to respire. They inhale oxygen to extract energy from food and exhale waste carbon dioxide. However, the bark can suffocate the wood inside, making it akin to breathing with a bag over one’s head. The green tissues might infuse the deep wood veins with fresh oxygen and absorb carbon dioxide waste.

Even a tree’s branches and twigs function in photosynthesis. All of this covert photosynthesis adds up to much more tree activity than initially perceived. Extra photosynthesis could result in a major energy boost for the tree in early spring, especially in trees that bloom before their leaves emerge. It could prove beneficial in repairing wounds and repelling pests. It reveals that trees function as more efficient power generators than previously assumed. Previously, roughly half of the carbon fixed through photosynthesis was believed to be lost via the tree’s respiration. Presently, it appears that trees have the opportunity to soak up another batch of carbon dioxide, decreasing waste. From a broader standpoint, this signifies that a significant amount of carbon dioxide is being locked away in forests, safely removed from harm’s way in this era of climate change.


  • davidwong

    David Wong is a 29-year-old educator and blogger who focuses on helping students learn in creative and interesting ways. He has a background in teaching and has been blogging since 2006. David's work has been featured on a variety of websites, including Lifehack, Dumb Little Man, and The Huffington Post.