October 13, 2014

Pick up your table’s journals.Write “Forces in Plants” in the table

of contents.Forces in Plants page 20

Introduction

When someone touches you, you turn and look.When you hear a loud noise, you may jump.

These are known as STIMULUS and RESPONSE.Something happens and causes another thing to

respond.

TROPISMS

• In plants, a response to a stimulus is called a TROPISM.

Forces cause the plant to respond.There are several different tropisms that you will need to know:

Back up to page 18

• Geotropism (Gravitropism) – a plant’s response to the force of gravity

Roots grow down – stems grow up(positive) (negative)

Phototropism – A plant’s response to light – grows toward the

light

Thigmotropism – a plant’s response to touch

Turgor pressure – force of water pushing against cell walls in plants

Gravitropism (geotropism)

Phototropism

Thigmotropism

Hydrotropism

Turgor Pressure

• Force of water pushing against cell walls in plants.