Tropism refers to the growth response of plants towards or away from an external stimulus and comes from the Greek word meaning "to turn". There are several types of tropism defined in the document, including phototropism (movement towards/away from light), geotropism (movement towards/away from gravity), thigmotropism (movement towards/away from touch), and hydrotropism (movement towards/away from water). Each of these tropic responses are important for plants to obtain resources like light, water, and minerals needed for photosynthesis, growth, and survival.

2. Tropism
 a growth response which a plant makes
with respect to a directional stimulus.
 plant movement towards or away from a
stimulus.
 came from the Greek word “tropos” which
means to turn.

3. Tropism
Positive Tropism
 towards the
stimulus
Negative Tropism
 away from
stimulus
Types of Tropism:
1) Phototropism
2) Geotropism
3) Thigmotropism
4) Hydrotropism

4. Phototropism
 movement towards or
away from light
tropos = to turn
photo = light
Importance:
 Increases the probability of stems and leaves
intercepting light for photosynthesis
 Roots obtain water and dissolved minerals that
they need.

5. Phototropism

6. Geotropism
 movement towards or
away from the earth
tropos = to turn
geo = earth
Importance:
 Roots will be more likely to encounter water and
minerals,
 Stems and leaves will be better able to intercept
light for photosynthesis.

7. Geotropism

8. Thigmotropism
 movement towards or
away from touch
tropos = to turn
thigma = touch
Importance:
 Thigmotropism by tendrils allows plants to
“climb” objects and thereby increases their chances
of intercepting light for photosynthesis.

9. Thigmotropism
Positive Thigmotropism

10. Thigmotropism
Negative Thigmotropism

11. Hydrotropism
 movement towards or
away from water
tropos = to turn
hyrdro = water
Importance:
 This ability to bend and grow the root towards a
moisture gradient is essential because plants need
water to grow.

12. Hydrotropism