Chapter 25 Plant Responses and Adaptations.

Set Up Foldable

• Fold Long and Skinny (hotdog)

• Fold short and fat 2 times (hamburger)

• Open so looks like below, crease is on top

What is a tropism?

Tropism ~ a response of a plant to an environmental

stimulus.

Tropism

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

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

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

What is phototropism?

Phototropism ~ a tendency of plants to grow toward a

source of light.

Phototropism• Phototropism is a

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

• The stalk displays positive phototropism growing towards the light.

What is gravitropism?

Gravitropism ~ a tendency of a plant to grow in a direction

in response to the force of gravity.

What is thigmotropism?

Thigmotropism ~ the response of plants to touch.

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.

Hydrotropism • Hydrotropism is a

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

• The roots display a positive hydrotropism growing towards water.

Turgor Pressure

• http://www.kscience.co.uk/animations/turgor.htm• Click on link above for example

The cell’s vacuole does not have any water in it.

The cell is flaccid.The vacuole does not have a lot of water in it.

The vacuole and cell wall push against each other.The vacuole is now full of water.