By : ILLANI BINTI IBRAHIMSCIENCE TEACHER

MRSM TAWAU

Stimuli and responses in Plants

? TROPISMS

The response of plants to a stimulus in a particular direction

PHOTOTROPISM

GEOTROPISM

HYDROTROPISM

THIGMOTROPISM

-Growth movement shown by plants in response to LIGHT.

-Shoots grow towards light ->POSITIVE PHOTOTROPISM

-Roots grow away from light.->NEGATIVE PHOTOTROPISM

-Growth movement shown by plants in response to GRAVITY.

-Roots always grow downwards - in the direction of gravity

->POSITIVE GEOTROPISM-Shoots grow upwards away from gravity. -

>NEGATIVE GEOTROPISM

-Growth movement shown by plant in response to WATER.

-Roots grow towards water.->POSITIVE HYDROTROPISM-Shoots grow away from water. -> NEGATIVE HYDROTROPISM

-Response by plants to TOUCH or contact with solid structure

-Climbing plants - have weak stems and tendrils to support their own weight such as cucumber and morning glory

-Ensures that these plants can grow upwards - towards the sunlight.

? NASTIC MOVEMENT

-The direction of responses do not depend on the direction of the stimuli.

-Plants responses to external stimuli from any direction-Example :

Mimosa plant Venus fly

trap