1. Plant Responses

3. Tropism A plant’s growth response toward or away from a stimulus. Positive if it grows TOWARDS the stimulus. Negative if it grows AWAY from the stimulus. These can be in response to LIGHT, TOUCH OR GRAVITY.

4. Light Light =PHOTO Phototropism is when a plant grows toward the light. This is positive.

5. Gravity Plants’ roots grow down while the stems and leaves grow up. Gravity comes from the center of Earth. GRAVITROPISM So ROOTS-show positive gravitropism So STEMS (shoots) and leaves show negative gravitropism A plant laying on its side will have the stems grow up toward the sun and the roots grow downward

6. Touch Thigmotropism– growth in response to touch Vines, green beans have tendrils that will coil around a wire, fence or another tree.

7. touch

8. gravity

9. light

11. Hormones Plants have hormones that cause them to respond to these stimuli. They also control other activities such as germination, formation of flowers, shedding of leaves, etc.

12. Seasons Photoperiodism-a response to a seasonal change based on the amount of light and darkness each day. Short day—means they like long nights so they bloom in the fall and winter. Ex-poinsettia Long day mean they like short nights so they bloom in the spring and summer. Ex.-clover Some must have a certain number of hours of darkness— critical night length Others are not sensitive to periods of light and dark and are called day –neutral plants.

13. Dormancy Inactive period Deciduous—lose leaves all at one time to survive freezing temperatures and lack of liquid water. – The chlorophyll actually breaks down to reveal the hidden colors of red and yellow. Evergreen- can keep leaves all year b/c leaves are needle shaped and help snow fall off of them and conserve water loss.

14. Life span Annual-plants live one year Biennials-plants complete a 2 year life cycle Perennials-plants that live for many years