Chapter 41: Plant Responses

Tropism: a plants growth response to an external stimulus (coming from one direction) eg. sunlight, gravity.

Plants growth response to an external stimulus (coming from one direction) eg. sunlight, gravity.

• Sunlight
• Gravity

• Phototropism: a growth response of a stem towards light
• So plant can receive maximum amount of light for photosynthesis.

Phototropism

Plant can receive maximum light for photosynthesis.

Phototropism

• Geotropism: a growth of response of a plant to gravity.
• Allows roots to get the water and nutrients it needs from soil and raises leaves up into light for photosynthesis.

• Geotropism
• Allows roots to get the water and nutrients it needs from soil and raises the leaves up into the light for photosynthesis.

Allows roots to get water and nutrients from soil and raises leaves up into light for photosynthesis.

Geotropism, response to gravity

• Thigmotropism: a growth response of a plant to contact.
• Eg vines wrap around objects to help support the plant.

Thigmotropism

Vines wrap around objects to help support the plant.

• Hydrotropism: a growth response of roots to water.
• Roots will grow towards water.

Hydrotropism

Water (hydrotropism)

• Chemotropism: a growth response of a plant to chemicals.
• Eg pollen tubes growing down the carpel in response to chemicals released by the ovule

• Chemotropism
• Eg pollen tubes growing down the carpel in response to chemicals released by the ovule. Ya

Pollen tubes growing down the carpel in response to chemicals released by the ovule.

Pollen tubes grow down the carpel

In response to the chemicals produced by the ovule

Pollen tubes grow down the carpel in response to chemicals released by the ovule.

Grow down carpel in response