What factor makes plant and animal to grow against the gravity?
Different parts of plants grow with or against gravity. For example, the shoots of a plant tend to grow against gravity, toward the light. But the roots of the same plant grow with gravity toward the center of the earth. This is a system called GRAVITROPISM or geotropism in all plants and fungus. We have a similar system that helps us walk, so do most all animals. Charles Darwin was one of the first to scientifically document that roots show positive gravitropism and stems show negative gravitropism. That is, roots grow in the direction of gravitational pull (i.e., downward) and stems grow in the opposite direction (i.e., upwards). This behaviour can be easily demonstrated with a potted plant.
