Plant Responses and Adaptations

1. Plant Responses and Adaptations

2. Hormones • Just like animals, plants rely on hormones to control growth and development, and responses to environmental stimuli • Recall that hormones are chemical messengers that signal changes in an organism

3. The hormone Auxin • Is a plant hormone that causes both phototropism and gravitropism • This hormone also control when new branch appears

4. Phototropism • Is the tendency for a plant to grow toward a light source • Auxins stimulate cell elongation and are found in high concentration on shady side of plant stems and are produced at the apical meristem http://www.answers.com/topic/phototropism

5. Gravitropism • Is the response of a plant to the force of gravity • It causes roots to grow downward and stems upward, no matter the plant/seed orientation

6. Cytokinins Hormones • Cause dormant seeds to sprout and stimulate the growth of new branches • Auxins inhibit new branching until plant is ready, but cytokinins actually cause the growth

7. Gibberellins • Produce dramatic increases in size of a plant, particularly in the stems and fruit • Also causes early and rapid growth of a plant

8. Ethylene • Stimulates fruits to ripen (plants all naturally release this slowly due to auxin responses) • Artificially used in commercial settings to ripen fruit that was picked un-ripened 

9. Plant Responses • Tropisms—are all responses to external stimuli • 1. Gravitropism • 2. Phototropism • 3.Thigmotropism • The response of a plant to touch • https://www.youtube.com/watch?v=BLTcVNyOhUc

10. Photoperiodism • This is the response that plants have to periods of light and darkness • Short-day plants—flower when the days are short • Long-day plants—flower when the days are longer

11. Dormancy • Is the period of time in which an organisms growth and activity dramatically decreases or stops • As cold weather approaches, deciduous plants turn off photosynthesis and transport important nutrients that are in the leaves to the roots • This is why plant leaves turn yellow/red in the fall

13. Plant Adapations

14. Aquatic plants • Water environments are typically really low in oxygen • Typically have tissues with large air filled spaces through which oxygen can diffuse

15. Desert Plants • Plants that live in the desert are called Xerophytes • Plants adaptations in the desert include extensive roots, reduced leaves, and thick stems that store water

16. Nutrition Specialists • These are plants that have specialized features for obtaining nutrients • Both • Carnivorous—eat other organisms for survival ie. the venus fly trap 2. Parasites—don’t run photosynthesis, harvest another plants nutrients .iemistle toe

17. Epiphytes • These are plants that grow directly on the bodies of other plants, they aren’t tied to soil • Most get their water from rain capture

18. Chemical Defenses • Many plants defend themselves against insects and other herbivores by manufacturing compounds that have harmful effects on these animals

19. Physical Defenses • Plants also defend themselves by building structures on their bodies the prevents herbivores from eating them