You are looking at the underside of a Douglas fir tree needle. Can you believe the detail?
You may have noticed while walking through Stanley Park or other coastal temperate rainforests, that the underside of the needles of the Douglas fir trees has two very distinct light green lines. In the close-up photo, you can see the individual cells that make up those lines. The next time you look at a Douglas fir needle, note that those lines you see are roughly six cell rows thick. The biggest circles you can see are not actually cells, but openings between cells.
What’s really interesting about these lines, and the cells that compose them, is that they are the primary site of gas-exchange for the Douglas fir tree. All of the oxygen and carbon dioxide transferring required for photosynthesis and respiration occurs through the large openings that you can see in the close-up photo. The important cells surrounding the openings are called stomata cells, derived from the Latin word stoma meaning mouth.
So what is this? This is the mouth-like cells on the underside of a Douglas fir needle that open and close to allow the tree to breathe. Cool right?