Responses Flashcards
(23 cards)
What is tropism?
The response of a plant to a directional stimulus
How do plants respond to a stimulus?
By regulating their growth
What is a positive tropism?
Growth towards a stimulus
What is a negative tropism?
Growth away from a stimulus
What is phototropism?
Growth of a plant in response to light
How do shoots respond to phototropism?
Positively phototrophic and grow towards light
How do roots respond to phototropism?
Negatively phototrophic and grow away from light
What is gravitropism?
Growth of a plant in response to gravity
How do shoots respond to gravitropism?
Negatively gravitropic and grows upwards
How do roots respond to gravitropism?
Positively gravitropic and grow downwards
How do plants respond to a directional stimulus?
By using specific growth factors
What are growth factors?
Hormone like chemicals that speed up or slow down growth
How do growth factors work?
Produce in the growing regions of a plant and move to where they are needed
What do auxins do?
Stimulate the growth of shoots called cell elongation (cells become lose and stretchy so cells get longer)
What do high concentrations of auxins do?
Inhibit growth in roots
What is indoleacetic acid (IAA)?
An important auxin that’s made in the tips of shoots in flowering plants
How and why is IAA moved around the plant?
IAA is moved around the plant to control tropisms. It moves by diffusion and active transport over short distances and via the phloem over long distances. This results in different parts of the plant having different concentrations of IAA
What does uneven distribution of IAA result in?
Uneven plant growth
Where does IAA move to due to phototropism?
IAA moves to the more shaded parts of shoots and roots
Where does IAA move to due to gravitropism?
IAA moves to the underside of shoots and roots
Why do simple mobile organisms have simple responses?
To keep them in favourable environments
What is a tactic response (taxes)?
Organisms move towards or away from a directional stimulus (e.g. light)
What is a kinetic response (kinesis)?
Organisms movement is affected by a non directional stimulus (e.g. humidity)
