Chew on This!

By Boak Wiesner

The first snow of the year fell on me as I made my way around “rhododendron corner.” From hot sun beating down just two days ago, now comes the first snow showers of the year. The rapidity of transitions of the moment-by-moment weather these days astounds me.

Trees still have plenty of foliage on them; the wet conditions of late have allowed trees to absorb plenty of water.  (If you look closely, the small white streaks show falling snowflakes.)

057Water and dissolved nutrients are absorbed from the ground into the roots, taking a couple of routes, either through cells, or around them through the cell walls, on the way to the center of the root where the xylem is. Xylem looks like a big, round collection of thousands of skinny straws; it’s the bulk of the trunk of the tree. As water evaporates out of the leaves, it pulls water behind it along because it’s so sticky to itself. Usually only the outer layers of xylem are engaged in transporting waters.

094Once in the leaves, some of the water is ripped apart by chlorophyll, thus beginning the process of photosynthesis. The sugars produced then flow back down the trunk in the phloem, which is just a thin layer of cells on the inside of the bark. When animals eat bark, it’s this layer and another thin one called the cortex they are after; they leave the xylem alone. At the end of the branches, the relative amount of bark to wood is the greatest, so deer and other animals nibble them off for food. This is the food group called browse.

Summer’s bounty is now available for animals to eat as they prepare for the coming, er, present winter. Trees use some of their energy to reproduce, of course, developing flowers to get their eggs fertilized through pollination. Then they wrap those babies in fruits in an attempt to get those seeds dispersed. Nuts and fruits, when they’re eaten as food, are referred to as mast: hard mast and soft mast.

061

083Sometimes the sheer aptness of names for things impresses me. Take Red Oak. Some of the summer’s sugars are transformed into the red pigment anthocyanin, which trees use to protect their photosynthetic “apparatus” and to help them reabsorb nutrients out of their leaves before they fall off. When this happens, very little if any water moves through the trees.

067Another apt name is Rhododendron: “red tree”. As the fall progresses, more of the leaves will turn this brilliant red.

079Boak Wiesner is a Minnesota Naturalist volunteer.

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