by Barbara Walvoord
from Lathrop Lamp Post, March 30, 2017
A bruised branch we see in the woods these days is likely to be oozing sap. As we drive through our countryside, smoke rising from a shack along the road tells us the inhabitants are “sugaring.” Those of us who don’t do our own “sugaring” trek to the Hadley Sugar Shack for pancakes drowned in real maple syrup.
Behind this common New England scene lie some amazing physics. Sap flows because of carbon dioxide–yes, that gas we have too much of, causing climate change. But inside a tree, carbon dioxide is essential. A tree has a problem–it has to get nutrients and water to its branches and roots, especially in spring when it’s trying to nourish new shoots and buds. It can’t burn coal for electricity, as we do to move heat and water through our homes. Instead, a tree uses the properties of carbon dioxide, and the spring changes in temperature, to push around the life-giving sap.
Sap flows through a portion of the outer tree trunk called sapwood. Sapwood consists of actively growing cells that conduct water and nutrients (sap) from the roots to the branches of the tree. During the Continue reading The Physics of Sap