I love the young bark of bigleaf maples. The green and white stripes on the surface are broken and cracked creating a beautiful pattern that reminds me of the skin of a watermelon.
The young stems of trees can be green and it is usually in the beginning of growth. From my observation, this can last for years before the bark thickens and starts to turn gray or brown in most trees. The stem pictured here is a sprout growing from the base of a big leaf maple, and I estimated it to be around seven years old or more. According to the Oregon Wood Innovation Center of Oregon State University, a bigleaf maple can reach 300 years of age, so I count this as still beginning growth.
Chlorophyll is the green pigment, present in all green plants that is responsible for the absorption of light to provide energy for photosynthesis. So I imagine that the stem of this tree can photosynthesize. I wonder if photosynthesis in young stems occurs just as much in the winter when the stems aren’t mostly covered in the shade of the canopy of leaves as in the summer.
Stomata are small pores on leaves that play a central role in photosynthesis by allowing carbon dioxide to enter the leaf and oxygen to exit the leaf. So my next thought was how does the exchange of gases occur in the stem if it is photosynthesizing?
The Royal Horticultural Society had this to say on their website: “Leaves and soft, green stems have living cells in contact with the air, and they can absorb oxygen for respiration directly through their surface. However, the bark of woody stems is impervious to gases, so to get oxygen to the active tissue beneath, it is perforated by pores called lenticels.”
In the photo above, I think the woody little bumps are lenticels. When reading about lenticels, the articles were about them absorbing oxygen and releasing carbon dioxide and water vapor during respiration. I haven’t found any articles involving lenticels and photosynthesis yet. As a side note, I thought that it was interesting that apples, potatoes, and avocados have lenticels too.
I am still researching photosynthesis in the green bark of trees, but I thought I would share some of what I have learned so far to get you interested in reading about it too.
Resources
Bigleaf Maple (Acer Macrophyllum) | Oregon Wood Innovation Center. https://owic.oregonstate.edu/bigleaf-maple-acer-macrophyllum#:~:text=Size%2C%20Longevity%2C%20and%20Form&text=Bigleaf%20maple%20is%20moderately%20long,after%2050%20to%2070%20years. Accessed 20 Feb. 2024.
How Plants Breathe / RHS Gardening. https://www.rhs.org.uk/advice/understanding-plants/how-plants-breathe. Accessed 20 Feb. 2024.
Check this out. Out in the south meadow, some bigleaf maples are growing out in the full sun and the young bark on the stems is red. Can these photosynthesize too? Why are they red?