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.