28. Plant Response Flashcards
Stimulus def.
Any change in the environment which causes an organism to react/grow
Response def.
Is the reaction to the stimulus
eg. growth
Tropism def.
The change in growth of a plant in response to an outside stimulus.
Positive tropism
Growth is towards the stimulus
eg. shoot in response to gravity
Negative tropism
Growth is away from the stimulus
eg. root in response to gravity
Tropism types
Geotropism-gravity Phototropism-light Thigmotropism-touch Chemotropism-chemicals Hydrotropism-water
Phototropism def.
Negative/positive in shoots/roots
Growth response to light
Negative: Roots grow away from light
Positive: Shoots grow towards light
Geotropism def.
Positive/negative
Def: Growth response to gravity
Neg: Shoots
Pos: Roots
Thigmotropism def.
example
Growth response to touch/contact
Vines wrap around objects which help support the plant
Chemotropism def.
example
Growth response to chemicals
eg. Pollen tubes grow down carpel in response to chemicals released by ovule
- Roots towards fertilisers in the soil
Hydrotropism def.
example
Growth response to water
eg. roots grow towards water
Advantage of tropisms
Allows plants to have the best conditions for growing.
eg. growth towards light so more light, more photosynthesis
What are internal factors affecting growth n a plant
Growth regulators
either growth inhibitors or promoters
Plant growth regulator def.
produced
transported by
Def: A chemical that controls the growth in a plant
Produced: Meristems regions-tips of roots and shoots
Transported by the phloem
Growth promoter def.
Increase rate of growth
eg. auxins such as IAA