Apogeotropism refers to the upward growth of a plant in response to gravity, especially when the plant is in a horizontal position. Some synonyms for apogeotropism include negative geotropism, anti-gravitropism, and upward gravitropism. These terms describe the same phenomenon, where a plant grows in a direction that is opposite to the gravitational pull. Other synonyms for apogeotropism may include hyponasty, which refers to the upward bending of a plant stem due to increased growth on the lower surface of the stem. In contrast, epinasty describes an abnormal downward bending of a plant stem due to increased growth on the upper side of the stem.