Woody Stem / Woody Root
Image and Text Source - TREES, ASSOCIATES, and SHIGO (2 CD set).
This sample is from a Honey Locust Tree. Gleditsia triacanthos.
Some anatomy differences.
1. Woody stem has a green cortex, the woody root has a cortex that is not green.
2. Woody stem stores a moderate amount of starch in living cells. Woody roots store a large amount of starch in living cells. This sample was stained with I²KI. The stain turns starch grains purple. You can see more purple to black in the woody root.
3. The woody stem has a pith. The woody root does not have a pith.
4. The woody root has a moderate amount of lignin. The woody stem has a much greater amount of lignin. If you were to cut a woody stem with a hand saw and then a woody root, you would see that the woody stem would be much harder to cut due to a greater amount of the cementing substance called lignin.
5. In this sample you can see that the vessels in the woody root are larger and more diffuse making the woody root more difficult to differentiate between the growth increments compared to the stem.
The list goes on.
Woody roots are organs that:
1. Anchor the tree.
2. Transport free water and substances dissolved in it.
3. Store energy reserves and hold water.
4. Make substances essential for the life of the tree.
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