Civil disobedience in trees

Generally we think of trees as passive, as silent giants at the mercy of our axes and chainsaws. I have reason to think differently, and here’s why.

I’m lucky enough to live by a big 2000 acre woods near a reservoir, and I’m in there walking all the time. There are many paths for walking, and some roads that are off limits. The rangers have post signs on trees on those roads. When I look at the signs (from the allowed trail, of course), I’ve noticed that some of the older signs are starting to get “eaten” by the trees. Really.

Think trees are powerless? / These trees eat signs! / Power is slow. Power takes time.

So, how would a scientist explain this? I suspect the first step is to imagine how a tree grows. Trees don’t just grow *up* they also grow *out*. Luckily, there are also many examples of cross sections of trees in the woods. Here are two examples.

A tree trunk is basically a transport mechanism for two things: the sugars made in the leaves during photosynthesis go down to the roots for storage (the phloem), and the water in the ground gets “sucked up” by the tree as a raw material for photosynthesis (the xylem). How does water flow up a tree? That’s a great question, and perhaps worthy of a another post. For a nice diagram and explanation see this website (http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_gateway/green_world/planttransportrev1.shtml).

The outer ring on the left tree is the xylem, the inner core is the phloem. However, the xylem is “dead”. How do “dead” cells eat signs? I’m not sure about this. I’ll have to wonder some more. In the meantime, more examples.

If you have ideas, feel free to share them with me!

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