When researching “why leaves fall off [deciduous] trees,” I found answers to several other Qs, e.g. “how does a ? know when to start shedding ???” and “what causes ?? to fall off ???” (Answers are generally “changes in day length” and “trees grow a special layer called abscission cells at the base of stems, causing leaves to break off easily, sometimes with help of special enzymes to ‘cut’ the layer.”) These didn’t really answer *why*, though. Why ditch perfectly good leaves that you worked all year to grow? What’s the strategy here?
It largely has to do with minimizing operating expenses (stay with me.) If you think of a tree as a factory powered only by solar panels, you can imagine that it could get expensive to keep the factory up and running during the winter. With such short days, you might be operating at a loss. It’s essentially “cheaper” for the factory/tree to hoard power to live on over the winter, ditch the solar panels, and manufacture them again when the days get longer.
The other issue that this strategy avoids is frost damage.❄️ If you turn on your factory in the middle of winter because it’s a beautiful sunny day, only to have your brand new solar panels ruined by a hailstorm that night, you may anger a few shareholders. ? Leaves are super susceptible to frost damage. (Also, unlike electric solar cells, photosynthesis doesn’t get more efficient at colder temperatures. )
Evergreen trees ? have a different strategy altogether. Their needles are less susceptible to frost damage due to their shape (the trade off is that they’re less efficient at photosynthesis due to a smaller surface area.) They also have a waxy coating to help protect them (and to help prevent water from escaping, a big deal when it’s drier in the winter.) This allows them to simply power their factories down in winter rather than pulling out the bulldozer. They still shed leaves, but they shed year round rather than “blowing their coat” all at once like a deciduous tree or a Husky.
Is your dog a “year round shedder,” or do they blow coat with the seasons like a deciduous tree? ?♂
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