3 days ago I put a seed in a wet soil and today when I wake up I saw a 4 or 5 cm vegetable. It leads me to the following question(s) : How did it know to grow "upward", that is where there is light. Is it because the seed can "feel" the light? Or because the seed can feel the gravitational acceleration direction? If it is the former then what would happen if I have a vertical jar without bottom, full of soil and I put 2 light bulb, one at the top, one at the bottom? In what direction would the vegetable grow? Another related question : If instead of a vertical jar I have a horizontal one and I put a light bulb at the left and another one at the right of the jar, in what direction would the vegetable grow? (Assuming that it is perfectly at the center of the soil, so that the seed receive an equal amount of light on each side). I could also ask the same question if I have a spherical soil without any jar and light coming from all directions. If it is the latter what would happen in case I put the seed in a vertical jar with no bottom, in what direction would grow the vegetable? Last question : is it the same for any seed/vegetable/tree? Thanks a lot!