Plant Tropisms

The movement or growth of a plant in response to a

stimulus…

ENVIRONMENT

The environment of an organism is made up of all of the factors that affect it. A habitat is a zone with a certain range of factors, such as a savannah.

An organism has adaptations that help it survive in its habitat. The better adapted it is, the more chance it has of successful reproduction – survival of the fittest.

Plant Responses (Tropisms)

Tropism is growth in response to an external stimulus (Stimulus is a factor that elicits a response).

Positive tropism: Plant growth toward a stimulus (Ex. water, sunlight)

Negative tropism: Plant growth away from a stimulus (Ex. spilled gas, toxins, too much sun or not enough)

So, plants can move to respond to the environment.

The stimuli for growth may be:

Light Temperature

Water Chemicals

Gravity Touch

Some of these ways are:

Phototropism Geotropism Hydrotropism Thigmotropism

Phototropism

Phototropism is a change in the growth of a plant in response to light.

The stalk displays positive phototropism growing towards the light.

Why?Maximize amount of sun for photosynthesis to make their food.

Positive Phototropism

Plant

Illustrate phototropism on your paper. Label your illustration as you would any scientific drawing. (See rules on your paper!)

This stalk displayspositive phototropismgrowing towards the light.

Time Lapse of Plants Following Light

https://www.youtube.com/watch?v=wjZ1UYwrO8A

Corn Dance

After 3 days of growth in darkness, the pot of corn seedlings in this movie were exposed to light from a single light bulb placed in the center of the pot just above the seedling. The plants were then imaged at 10 min intervals for about 18 hours. For the first 14 hours the seedlings appear to be dancing to the light as they maintain phototropic curvature. Since geotropism is simultaneously affecting the seedlings, the curvature that develops is a compromise between the opposing light and gravity responses. After 14 hours, the point light source was turned off and diffuse room lighting was turned on, at which point geotropism becomes the dominant stimulus and the seedlings quickly return to a vertical orientation. Frame playback is at 12 frames per sec.

https://www.youtube.com/watch?v=RZDwoteRuqA

Geotropism (Gravitropism)

Geotropism is a change

in the growth of a plant

in response to gravity.

The stalk displays a negative geotropism growing away from

gravity.

The roots display a positive geotropism growing towards gravity.

Negative

Positive

Write the definitions and illustrate them. Label your illustration as you would any scientific drawing.

NegativeGeotropism

Illustrate geototropism on your paper. Label your illustration as you would any scientific drawing. (See rules on your paper!)

This stalk displaysNEGATIVEphototropismgrowing away fromthe gravity.

PositiveGeotropism

Illustrate geototropism on your paper. Label your illustration as you would any scientific drawing. (See rules on your paper!)

The roots displayPOSITIVEphototropismgrowing towardsgravity.

Gravitropism

http://www.youtube.com/watch?v=8SkKuwbmR5Y&feature=related&safety_mode=true&persist_safety_mode=1

Why?Allows plants to grow properly and get nutrients and sunlight

Geotropism(Gravitropism)

https://www.youtube.com/watch?v=mYZXax8V_L0

Phototropism and Geotropism Time Lapse Montage

https://www.youtube.com/watch?v=F3Oj2er-91s

Hydrotropism

Hydrotropism is a change in the growth of a plant in response to water.

The roots display a positive hydrotropism growing towards water.

Positive

Water

Write the definition and illustrate it. Label your illustration as you wouldany scientific drawing.

Hydrotropism

Why? Roots search for

and grow toward water, because it is needed for photosynthesis and to support cell structure.

Positive

Water

Write the definition and illustrate it. Label your illustration as you wouldany scientific drawing.

Thigmotropism

Thigmotropism is a movement in which an organism moves or grows in response to touch or contact stimuli.

Thigmotropism

usually occurs when

plants grow around a

surface, such as a wall,

pot, or trellis.

illustrate thigmotropism. Label your illustration as you wouldany scientific drawing.

https://www.youtube.com/watch?v=m2xKjA69jNM

Thigmotropism

Why? to support leaves

as they grow higher to reach the sun to make more food (photosynthesis).

Label your illustration as you would any scientific drawing.

NASTIC RESPONSES are fast, reversible movements and are non-directional. The movement can be caused by changes in turgor pressure or changes in growth.

http://www.youtube.com/watch?v=O7eQKSf0LmY

Hungry Venus flytraps snap shut on a host of unfortunate flies. But, despite its name, flies aren’t the flytrap's only meal. As long as its prey is roughly the right size and touches two of its hairs within twenty seconds, the plant will dine on any insect or spider that comes its way. Glands in the lobes then secrete enzymes that break the dinner down into a digestible soup. Ten days later, the trap pops open to reveal nothing but a dried out husk.

Venus Flytraps: Jaws of Death - BBC One

Mimosa Pudica – The Sensitive plant

https://www.youtube.com/watch?v=BLTcVNyOhUc

Plants in Action

We tend to think of plants as being essentially stationary incapable of movement other than that generated by the wind. But all plants do move as they grow and respond to aspects of their environment.

https://www.youtube.com/watch?v=zmxY6aD7ltM