TROPISM Plant growth in response to a stimulus (Something that causes a response; water light, gravity, touch)

What is

tropism?

There are many types of tropisms :

• Phototropism

• Geotropism

•Thigmotropism

• Hydrotropism

• Chemotropism

• Thermotropism

(“tropo” – ”turn”)

What is

gravitropism?

(“Geo” – Earth)

the growth of a plant in response to gravity.

Positive Geotropism growth of a plant towards the center of the earth with gravity. (roots growing down)

Negative Geotropism growth of a plant away from the center of the earth-opposing gravity (stems grow up)

Negative Geotropism

Positive Geotropism

Why is

gravitropism so

important?

•Pulls roots down to anchor a plant • Roots can get needed water and minerals if they stay in the soil

What is

phototropism? (“Photo” – light)

The growth response of a plant in response to light direction

Ex. Stems growing

toward the window

to get to the light

Why is

phototropism

so important?

Enables leaves to be in the best position possible to receive adequate light for photosynthesis

What is

thigmotropism?

(“Thigmo” – touch)

the growth of a plant in response to touch/contact.

Vines growing on a wall or fence

Tendrils on a sweet pea