How do trees decide when and where their branches grow?
In: Biology
The trunk as it grows up taller and wider will grow some new places where branches might go. The trunk decides how often to make new branches by following a bit of math that tells it to make branches only as often as necessary to create armfuls of leaves that will cover the sky without covering each other. The trunk knows that branches it has grown are still alive because the leaves at the ends make a…well let’s call it a smell. As the Sun shines on the leaves and they grow they make a smell that the trunk can smell and that way it knows the branch is alive and won’t try to grow another branch at that spot. If the trunk doesn’t smell any leaves coming from a branch, it may start to try growing new branches in that spot. When a tree is cut down and only the trunk is left it won’t smell any leaves at all coming from above and it will try to grow branches all over the place to start anew. We call these “suckers” coming from the old stump and if they are left long enough then one of them will grow bigger and make many leaves and the smell of those leaves will come down to the stump and it will stop growing the other suckers and focus only on growing that one successful sucker and that’s how a tree may recover from being cut down.
So, in very short, leaves make a sort of smell that tells the trunk that it doesn’t need to grow another branch in that spot. The trunk will create new branches above old branches as it grows taller according to some basic math that helps it to spread branches out so they don’t overlap and cover each other from the Sun.
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