Tropism
Tropism is the directional growth or movement of a plant in response to an external
stimulus. This movement can be positive (towards the stimulus) or negative (away from the
stimulus). Since plants cannot move from place to place, they rely on tropisms to adapt to
their environment by growing in favorable directions
Types of Tropisms
1. Phototropism (Response to Light)
Positive Phototropism: Shoots and leaves grow towards light, maximizing photosynthesis.
Negative Phototropism: Roots grow away from light.
Mechanism: The plant hormone auxin accumulates on the shaded side of the plant, causing
cells there to elongate more and the plant to bend towards the light.
2. Gravitropism (Geotropism) (Response to Gravity)
Positive Gravitropism: Roots grow downward, anchoring the plant and seeking water and
nutrients.
Negative Gravitropism: Shoots grow upward, reaching for light.
Mechanism: Auxin distribution is influenced by gravity, promoting differential growth that
directs roots downward and shoots upward.
3. Hydrotropism (Response to Water)
Positive Hydrotropism: Roots grow towards moisture, ensuring the plant accesses necessary
water.
Negative Hydrotropism: Less common; roots grow away from moisture.Google
Sites+2BYJU'S+2Wikipedia+2
4. Thigmotropism (Response to Touch)
Positive Thigmotropism: Seen in climbing plants like vines; tendrils wrap around structures
for suppo
Negative Thigmotropism: Rare; parts of the plant grow away from touch stimuli.
5. Chemotropism (Response to Chemicals)
Positive Chemotropism: Pollen tubes grow towards ovules during fertilization.
Negative Chemotropism: Growth away from harmful chemicals.
6. Thermotropism (Response to Temperature)
Tropism is the directional growth or movement of a plant in response to an external
stimulus. This movement can be positive (towards the stimulus) or negative (away from the
stimulus). Since plants cannot move from place to place, they rely on tropisms to adapt to
their environment by growing in favorable directions
Types of Tropisms
1. Phototropism (Response to Light)
Positive Phototropism: Shoots and leaves grow towards light, maximizing photosynthesis.
Negative Phototropism: Roots grow away from light.
Mechanism: The plant hormone auxin accumulates on the shaded side of the plant, causing
cells there to elongate more and the plant to bend towards the light.
2. Gravitropism (Geotropism) (Response to Gravity)
Positive Gravitropism: Roots grow downward, anchoring the plant and seeking water and
nutrients.
Negative Gravitropism: Shoots grow upward, reaching for light.
Mechanism: Auxin distribution is influenced by gravity, promoting differential growth that
directs roots downward and shoots upward.
3. Hydrotropism (Response to Water)
Positive Hydrotropism: Roots grow towards moisture, ensuring the plant accesses necessary
water.
Negative Hydrotropism: Less common; roots grow away from moisture.Google
Sites+2BYJU'S+2Wikipedia+2
4. Thigmotropism (Response to Touch)
Positive Thigmotropism: Seen in climbing plants like vines; tendrils wrap around structures
for suppo
Negative Thigmotropism: Rare; parts of the plant grow away from touch stimuli.
5. Chemotropism (Response to Chemicals)
Positive Chemotropism: Pollen tubes grow towards ovules during fertilization.
Negative Chemotropism: Growth away from harmful chemicals.
6. Thermotropism (Response to Temperature)
