22 October 2014

X...

...is for Xylem...


...the tubes in a tree which transport water from the roots to the leaves.  The water travels by two methods, transpirational pull through negative pressure that pulls the water from the roots and soil or by root pressure, water traveling by osmosis (a difference in pressure) into the root from the soil  creating a positive pressure that forces liquid up the xylem.  As the water evaporates from the leaves more is drawn up through the tree to replace it.  These tubes only live for one year, new xylem are grown each year from the cambium, a layer of tissue between the inner bark (phloem) and the xylem.  As the tree grows the inner rings of xylem become the heartwood, the outer rings the sapwood.  

The dead xylem is visible as the rings of a tree when it is cut down.

Joining in with the Alphabet Photography Project

8 comments:

  1. Wow - great X and fab shot. Who knew I'd learn something like this through a photography project? :)

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  2. Ah good, something to help maintain my credibility with daughter studying A level biology!

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  3. I had forgotten they were called that. Brings back memories of labelling them on diagrams in Biology class. Great X. #AlphabetPhoto

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  4. I learned another new word today! Thank you ;) #alphabetphoto.

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  5. I'm sure I've said this before, but I'm always amazed by the stuff I learn from your posts! Great stuff xxx

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  6. What a brilliant X, and I learnt something new :) #alphabetphoto

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  7. I've learnt something new here today.

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