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A Tree and Its Trunk


Understanding the trunk of a tree is key to understanding how a tree works, and a primary reason why trees are so useful.  The trunk is the part of a tree that connects the leafy crown with its roots.  Roots absorb water and nutrients from the soil, which are then transported up the tree trunk in cells that act much like pipes.  This allows the leaves to obtain water and nutrients that are necessary for the manufacture of food from light energy (photosynthesis).   Food made in the leaves is then transported down to the roots and to other parts of the tree for growth.   The "pipes" in the trunk are known as vascular tissue.  It is this vascular tissue which we exploit to make paper and other forest products.
Wood is primarily made of xylem (tracheids in conifers, vessel elements in hardwoods) that behave very much like a bundle of straws. Try crushing a bundle of straws from the side. Next try crushing the same bundle of straws from the ends!

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