Is root bark different from stem bark in the Cerrado plant community?

What is it about?

Bark is the first thing we notice when we admire a tree, covering both stems and roots. However, bark serves more than just a decorative purpose: the outer bark protects the tree from environmental conditions such as sunlight, storms, and even fire, while the inner bark carries the sugars produced by photosynthesis throughout the plant. This raises an intriguing question: Is the bark uniform throughout the plant, from the roots to the stems? To answer this question, we studied the bark cells of the roots and stems of 15 species in the Brazilian savanna, a landscape where the stems are often exposed to fire while the roots remain protected. We found that the stem has a thicker outer bark with more protective traits in the cells, which increase fire resistance and defend against pathogens. On the other hand, the root has slightly more storage cells in the inner bark, which may help the plant survive and regrow after a fire. Therefore, the root bark is different from the stem bark, and these differences are essential for the plant to survive the fire. Furthermore, far beyond the fire, the bark has structures that facilitate gas exchange, named lenticels, that we hardly find in the stem, suggesting an alternative way of gas exchange in the stems. It highlights that there is still much to learn about bark.

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