1. Plant Tropisms

2. What are we talking about? Tropism - directional growth of a plant, or part of a plant, in response to an external stimulus

3. Stimulus Stimuli – an action or condition that causes a response Stimuli can be either internal or external

4. Types of Stimuli External stimuli- come from factors found in the environment. Examples- temperature, presence of water or nutrients, light etc Internal stimuli- come from factors within an organism Examples- germs, dehydration, lack of nutrients, etc.

5. Stimulus

6. Response An organisms reaction to change.

7. Response

8. What are we talking about? Stimulus – an action or condition that causes a response Response – an action or condition that is a reaction to a stimulus  Negative response – when the growth of a plant is away from the stimulus  Positive response – when the growth of the plant is towards the stimulus

9. Example Stimulus = Lack of water. Is this internal or external? Is this internal or external? Response = wilting Is it positive or negative? Examples

10. Homeostasis Homeo- same Stasis- state of balance The purpose of response to stimuli in organisms is to maintain homeostasis, a balance within it’s internal systems.

11. What are we talking about? Tropism - directional growth of a plant, or part of a plant, in response to an external stimulus Usually named for the stimulus involved

12. Types of Tropism Today we are going to be studying the types tropisms: Geotropism Thigmotropism Phototropism Thermotropism Heliotropism Hydrotropism

13. Hydrotropism Stimulus: Water Response: A plant’s roots grow towards the source of water IIIIs this a positive or negative response?

14. Thermotropism Stimulus: Temperature Response: a plant grows in the direction of/away from a source of heat or cold EEEExample: In the first picture, this tree has a positive response to the cold. EEEExample: A plant called a Rhododendron curls its leaves away when it experiences cold weather.

15. Geotropism/Gravitropism Stimulus: Gravity Reaction: PPPPositive – the roots grow downward, with gravity NNNNegative – the stalk grows upward, against gravity

16. Thigmotropism Stimulus: Touch Response – the leaves (or part of the plant that is touched) move or coil away from the touch, or trigger some other action  Example: The Venus Fly Trap is a plant that shows thigmotropism. It closes when a bug or some other object touches it.

17. Phototropism Stimulus: Light Response – the plant grows in the direction of a unidirectional light (it only comes from one direction)  What type of response is this?

18. Heliotropism Stimulus: Sunlight Response – a plant grows or turns to face the direction of the sun  Example: Young Sunflowers face the sun all day long. As the sun goes across the sky, the sunflower turns so that it is always facing it.  Is a Sunflower growing towards the sun an example of Phototropism or Heliotropism?

19. Working Together Plant tropisms work together to maintain homeostasis within the plant  Heliotropism  +Geotropism  -Geotropism  Hydrotropism

20. References Pictures:   http://virtualastronaut.tietronix.com/textonly/act25/images/hydrotropism. gif http://virtualastronaut.tietronix.com/textonly/act25/images/hydrotropism. gif   http://k53.pbase.com/u48/roving_rube/large/30489110.a.c.birch.jpg http://k53.pbase.com/u48/roving_rube/large/30489110.a.c.birch.jpg   http://www2.brevard.edu/jefrick/rhod.htm http://www2.brevard.edu/jefrick/rhod.htm   http://www.xtec.cat/~mherna23/summer03/amspot/picture/gravitropism. gif http://www.xtec.cat/~mherna23/summer03/amspot/picture/gravitropism. gif   http://img1.photographersdirect.com/img/17231/wm/pd1198793.jpg http://img1.photographersdirect.com/img/17231/wm/pd1198793.jpg   http://wpcontent.answers.com/wikipedia/commons/9/9d/Dionaea_musci pula_closing_trap_animation.gif http://wpcontent.answers.com/wikipedia/commons/9/9d/Dionaea_musci pula_closing_trap_animation.gif   http://img1.photographersdirect.com/img/17231/wm/pd1198796.jpg http://img1.photographersdirect.com/img/17231/wm/pd1198796.jpg   http://farm2.static.flickr.com/1423/1402179998_4e1712d584.jpg http://farm2.static.flickr.com/1423/1402179998_4e1712d584.jpg Information:   http://www.hasc.qld.edu.au/csnotes06/biowedGG/Notes%20for%20San dra/Plant%20Tropisms.doc http://www.hasc.qld.edu.au/csnotes06/biowedGG/Notes%20for%20San dra/Plant%20Tropisms.doc   www.wikipedia.org www.wikipedia.org