If a plant stem falls and continues growing it is thought that the stem bends upward when auxins are pulled to the bottom side of the stem by gravity. The bottom side then grows faster than the top side which causes it to bend upward. As the stem becomes upright again the auxins even out and the stem then grows straight. Most general botany books have information which may be clearer than my account. General botany books may be found in most libraries.
Plants grow against the pull of gravity.
I am not a plant type, but check the word geotropism. It is the effect of gravity on plants. Most plants have a negative reaction to gravity, that is they grow opposite the pull of gravity in order to get up above the soil. Yes, but it depends on which part of the plant you are asking about. Argonne National Laboratory, Division of Educational Programs, Harold Myron, Ph.D., Division Director.