Ontogeny: One Plant, Many Leaf Shapes
Here’s something I never knew about plants until I started paying attention: a single species can have different leaf shapes over the life of the plant. In fact, some can have different leaf shapes on the plant at the same time. For example, the four leaves below are all on the same plant.
All these leaves are alive on the plant right now. The ones on the left are older, the ones on the right are newer, but they’re all active and working.
I picked up this plant at a SF Botanical Garden sale, labeled only as “Philodendron from conservatory.” I have no idea what species it is, or even if it’s a hybrid. There aren’t many trilobed Philodendron, but I haven’t found one with such narrow side lobes. Plus, I don’t know if it’s done evolving yet. Its ultimate leaf shape may yet be different.
What’s going on here is called “ontogeny,” which is about how an organism changes size and shape over time.
Philodendron like this come from jungles, where early life is damp and dim. A thick canopy of trees blocks most light from reaching the ground, so plants evolved to have a juvenile, vine-like state that climbs to the top of the canopy. (“Philodendron” means “tree lover” because of their tree-climbing.) As they get closer to the top and light increases, the plant transitions to its adult leaves and becomes more bush-like. Eventually leaves can change shape and color so much that you’d never guess it was the same plant.
Many common houseplants are jungle natives that spend their lifetimes stuck in a juvenile state because they’re kept indoors, which is a lot more like the jungle floor than the canopy. This Philodendron, no matter how tall he grows, will never reach the jungle canopy of his dreams, but he will reach a bright window and I can’t wait to see if his leaves continue to change.
UPDATE: 17 May 2012: I think I found the parent plant.