It just seems like there’s so much wasted real estate with all that trunk space, even in the canopy, there’s light shining through. (palm tree’s are what first got me thinking on the topic).
In: Biology
Something I think the others are missing is why trees have trunks *at all*. Animals compete with each other for food, right? Well, plants do, too. In their case, the food is sunlight. There are different strategies to get sunlight. If a plant grows *out* with big, broad leaves it will catch a lot of sun. However, if another plant grows *up* it can grow over the broad plant and then grow out, in which case the tall plant is catching sunlight and casting shade over the short, broad plant.
Trees have evolved to grow tall, towering over lower plants so that the trees have access to sunlight without worrying about other plants growing over them and shading them. It also puts the soft, tasty leaves high above potential predators so few things can eat the leaves. But that means they have to have tough, strong trunks to hold up the weight of the rest of the tree. But that also leaves them with a particular vulnerability, which is a big open trunk full of nutritious sap that tons of animals would love to get a hold of.
So trees evolved a countermeasure, which is bark. Bark is thick and tough and essentially inedible. It isn’t living tissue and there’s no nutritional value in it. It’s armor to keep things from burrowing into the tree trunk. An insect trying to get to the sap has to first waste precious time and energy burrowing deep through the bark. Woodpeckers have needed to evolve some pretty astounding adaptations to smash their way through bark. When trees first evolved to produce lignin and bark, there was nothing that could chew through it at all.
All that bark gets in the way of photosynthesis. Chloroplasts won’t do anything buried under the bark, and putting them outside the bark would defeat the purpose of having bark at all, since it would put living tissues where predators could get to it.
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