2.80) Geotropism

Geo= gravity; Tropism =growth; Geotropism =plant's growth and response to the gravity

• If a root/stem grows toward the gravity (downward), then it is a positive geotropism. If it grows against the gravity (upward), it is the negative geotropism. 
• For example, on a seed there is the embryotic shoot which grows upward (negative) and embryotic root which grows downward (positive).
• One experiment is that we rotate the seed by 90degree so that both embryotic shoot and root are parallel to the ground.
• The embryotic shoot would continue to grow upward, and in the same time the embryotic root would continue to grow downward.  This proved that for different structure the plant would produce different but specific response to the environment (in this case, the gravity).