1. How do plants respond to their environment? Chapter 1 Lesson 4

2. Growth response A growth response of a plant toward or away from anything in its environment is called a tropism The work tropism comes from a Greek word that means “to turn”

3. The directional growth response of plants to light is called phototropism. The response of a plant to gravity is called gravitropism. – Growing toward the pull of gravity is called positive gravitropism – Growing away from the pull of gravity is called negative gravitropism

4. Other tropisms A plants growth response to touch is called thigmotropism. Hydrotropism is a plant’s growth to water. Plants also “track” the sun. This is called solar tracking. Facing the sun increases the amount of energy the plant can absorb.

5. Plant rhythms To survive, plants must adapt to the changing seasons. – Most plants grow when it’s warm and die or become inactive – dormant- when it is too cold. – To do this plants must respond to changes in temperature

6. Many plants also respond to changes in the length of the day. Long-day plants flower when there are more than a certain number of daylight hours. (despite the name, it actually depends on how the amount of darkness to determine when the plants bloom)

7. Short-day plants flower when there are fewer than a certain number of daylight hours. They need long periods of darkness in order to bloom.

8. Some plants germinate, flower, make seeds, and die within one growing season. These plants are called annual plants. Other plants return year after year. These plants are called perennial plants. *Images provided by Google and AltaVista