How Does a Plant Know Which Direction to Grow?

Imagine you're in the dark and someone taps your shoulder, you turn toward them. Plants do something similar, but they use special sensors to feel light and gravity. When a seed sprouts, it can tell which way is up by feeling gravity, and when it's growing, it turns toward the sunlight like a little sun-chaser. These sensors are called photoreceptors for light and statoliths for gravity.

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Examples

  1. A sunflower turns its head toward the sun just like you turn your face toward a friend calling out to you.
  2. If you plant a seed upside down, it still grows up because it knows gravity is pulling it down.
  3. A vine creeps along a wall and bends around corners as if it's following a path.

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