| A | B |
|---|
| hormone | chemical signal that is produced in one part of an organism and affects cell activity in another part |
| gibberellin | plant hormone that stimulates cell growth |
| ethylene | plant hormone that is produced in fruits and causes them to ripen |
| cytokinin | plant hormone that stimulates the final stage of cell division, cytokinesis; also involved in the growth of side branches |
| auxin | plant hormone that stimulates the lengthening of cells in the growing tip |
| tropism | movement or growth of a plant in response to an environmental stimulus |
| phototropism | growth of a plant toward a light source |
| thigmotropism | turning or bending of a plant in response to contact with an object |
| gravitropism | growth of plants in response to gravity; plant stems grow upward, against gravity, and roots grow toward the gravitational pull |
| photoperiodism | response of an organism to changes in the length of the day |
