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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