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Asked by Minecraft to Alex, Ana, Clay, Keegan, Mark on 23 Apr 2016.
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Mark Ritchie answered on 23 Apr 2016:
I assume the question was, “Where does wood on trees come from?”
Trees make wood for several reasons. Wood is a complex mix of two of the toughest chemicals we know – cellulose and lignin. Not many critters like to eat it, so it is great for building trunks and branches to get leaves higher and higher so they aren’t shaded out by other trees. Wood also makes the whole tree difficult to eat. The toughness of wood makes it unlikely that the tree gets blown over in a storm.
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Alexander Taylor answered on 24 Apr 2016:
The wood on trees comes from thin air! Well, and water, with a little help from the sun. During photosynthesis, plants use energy from sunlight to make sugar out of carbon dioxide from the air (the same stuff you breathe out when you exhale) and water. These sugars can then be built up into all sorts of tough, woody chemicals like cellulose.
A tiny amount of the weight of wood comes from nutrients in the soil that the plants take up from its roots (with the help of microscopic bacteria and fungi!) But if you weighed a tree trunk, most of that weight was originally carbon dioxide in the air.
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Clay Robinson answered on 25 Apr 2016:
Plant cells and animal cells are different. One of those differences is that plant cells have “walls”; these walls have cellulose in them. Cellulose is a special kind of carbohydrate. If you look at the label on a box of cereal, carbohydrates are listed as dietary fiber, sugars, and other carbohydrates. The other carbohydrates are starches. We get most of the energy we need to live from the starches and sugars we get from the plants we eat, especially from rice, wheat, corn, and dried beans. But our bodies cannot digest the dietary fiber. This is the cellulose found in the cell walls of plants.
The cell walls in trees are much thicker than in the plants we eat and contain more cellulose. As the cells die and dry, they become very dry and hard. These dead, dried and very hard cells are the wood we find in trees.
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