How does a seed know which direction is up and which down so the plant always grows to the surface but not the roots?

Question

How does a seed know which direction is up and which down so the plant always grows to the surface but not the roots?

In: Biology

Answer 1

They’ve germinated seeds in space, sans gravity, they use light to orient their growth.

https://www.nasa.gov/content/growing-plants-in-space