Plant Adaptation: Reaction to

StimuliDaisy Mae A. Valeroso

Plant Cell

Plants grow slowly !

PLANT RESPONSES

Stimulus – Response

Process

Stimulus- change in

the environment

that causes a plant

to react

Response- plant’s

reaction to a

stimulus

Makahiya Plant

Tropisms- Responses of

plants to stimuli

- Could be negative

or positive

Positive Tropism – when a plant moves toward

the stimulus

Negative Tropism – when a plant moves away

from the stimulus

Phototropism Geotropism

Hydrotropism

Plant Tropisms

(Responses to stimuli)

Geotropism

(gravity)roots

Phototropism

(light)

Hydrotropism

(water)

Hydrotropism

(water)

Phototropism

(light)

Geotropism

(gravity)

Stems and leaves

Stems and leaves

roots

Stems and leaves

roots

Positive

Negative

Phototropism

NegativePositive

Geotropism

Positive Negative

Hydrotropism

Positive Negative

Situation

There are grasses growing in a

horizontally cut truck tire. They have

positive phototropism and negative

geotropism on its leaves and negative

phototropism and positive geotropism

on its roots.

Directions: Write TRUE if the underlined word is correct and if

it is false, write the correct word to make the sentence correct.

______ 1. Roots move toward the source of water but away

from the direction of light. Roots have positive

geotropism and negative phototropism.

______ 2. The leaves of a plant placed near a window would

eventually face the direction of light. Leaves have

positive phototropism.

______ 3. The roots need water to survive, therefore, roots

have positive hydrotropism.

______ 4. See weeds have positive hydrotropism.

______ 5. The roots of the orchids move downward but

away from the sunlight. Its flowers always face

toward the sun. Therefore, its roots have negative

geotropism, negative phototropism and its

flowers have positive phototropism.

Assignment

Observe a hanging plant.

Identify its positive and negative

tropisms and explain the reason in 2

to 4 sentences. Write it on a sheet of

paper.