We all know that plants move, just that the motion is pretty measured relative to their brethren over in the animal side. This slow-motion dance is often the result of plants sensitivity to the gradual cycles of sunlight, darkness, warmth and cold.
Plants that seek the sunlight will twist and turn to follow the sun in an activity called positive phototropism.
On the other hand (or leafy appendage) some climbing plants, like vines, exhibit a very cool and remarkable behavior. If they become disconnected from the tree or structure that supports them and fall to the ground, the portion on the ground will move off in the direction of something else to climb. The strategy it employs is to basically move away from the light and toward the shadows, because darker areas are likely to mean the trunk of a tree or other vertical surface.
These vine stems are now *negatively* phototropic, growing away from the sunlight and toward the shade. Once the vine resumes its vertical climb, it switches back to its more normal positive phototropic behavior. As it grows upward toward the sun, its leaves become larger and larger to collect the maximum amount of the sun’s energy.
We humans like to place such plants in hanging baskets and let the vines trail down in artistic and dramatic ways. However when you understand the way these plants evolved and survived, we are basically hanging them upside down in a way that restricts their normal growth patterns.
When we think about vines and their complex behavior, we might conclude that these plants are in some sense thinking things through as we might, comparing and contrasting a risk/reward model and then making the “right” choice. But the reality — while not ours — is no less complex, happening way down at the molecular level where genes and enzymes interplay. Such mechanisms have been developing over millions of years and are happening right now, out there beyond your window in the light and in the shadows.
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