Thursday, April 28, 2011

X is for xylem

47  245/365  a new place to creep


why was it that for years I knew that trees got water from their root?

And then I knew that the water traveled by tubes called xylem, and that these tubes made up what we call wood and are responsible for the annual rings.

But why did I never ask... How does the water travel up the xylem?

short answer: it is pulled by the air outside the leaves

longer answer

4 comments:

  1. Oh goodie. My husband and I are excited about this one. He teaches 4th grade, and he loves biology. We've been talking a lot about this topic the last year, because last year was his first year to tap our maple trees for sap to boil down to syrup. (So so yummy.) I really love learning from you, and him, and knowing that the air, and the exchange of carbon dioxide and oxygen that the leaves do with it, are what pull the liquid up through the tree, defying gravity. It's so wonderful.

    My husband's next question: How do the trees do it in the spring, before leaves?

    ReplyDelete
  2. Can I make a guess here? First off before the leaves emerge there is little need for weather, also though those buds are tightly closed, I would hazard a bet that they are not air tight.

    That sure is a lot of liquid that flows down the phloem in the spring, maybe the moisture is drawn up by the movement of water going down. How cool would that be.

    too bad you live so far away, I am thinking it would be a hoot to have yuse (local plural of you)over for dinner.

    ReplyDelete
  3. That would be so cool. And we would bring a bottle of Michigan maple syrup.

    It's amazing that as soon as he pounds a spile into the tree, it starts to drip!

    ReplyDelete
  4. OK, I was way wrong, the sap is flowing up, I thought it was nutrients headed to the roots, but it is nutrients stored in the roots headed up. sending an e-mail with more info.

    ReplyDelete

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