Stimuli and Responses- Responses in Plants and Animals Flashcards
What do plants do once they sense the direction of light?
They grow towards the light to maximise light absorption for photosynthesis
What do plants do once they sense gravity?
Their roots and shoots grow in the right direction
Why do climbing plants have a sense of touch?
So they can find things to climb up and reach the sunlight
What is a tropism?
The response of a plant to a directional stimulus
How do plants respond to stimuli?
By regulating their growth
What is a positive tropism?
Growth towards the stimulus
What is a negative tropism?
Growth away from the stimulus
What is phototropism?
The growth of a plant in response to light
What are shoots in regards to phototropism?
They are positively phototropic and grow towards light
What are roots in regards to phototropism?
They are negatively phototropic and grow away from light
What is gravitropism?
The growth of a plant in response to gravity
What are shoots in regards to gravitropism?
Negatively gravitropic and grow upwards
What are roots in regards to gravitropism?
Positively gravitropic and grow downwards
How do plants respond to directional stimuli?
Using specific growth factors
What are growth factors?
Hormone-like chemicals that speed up or slow down plant growth
Where are growth factors produced and where do they move to?
They are produced in the growing regions of the plant and move to where they’re needed in the other parts of the plant
What are auxins?
Growth factors that stimulate the growth of shoots by cell elongation
What happens if there are high concentrations of auxins?
They inhibit growth in roots
What is indoleacetic acid (IAA)?
An important auxin that’s produced in the tips of shoots in flowering plants
Why is IAA moved around the plant?
To control tropisms
How is IAA moved around the plant?
By diffusion and active transport over short distances, and via the phloem over long distances
What are tactic responses (taxes)?
The organisms move towards or away from a directional stimulus
What are kinetic responses (kineses)?
The organisms’ movement is affected by a non-directional stimulus
