3 - Responses in plants Flashcards
What is a tropism?
The response of a plant to a directional stimulus
What is phototropism?
The growth of a plant in response to light
What is a positive tropism?
Growth towards the stimulus
What is a negative tropism?
Growth away from the stimulus
Are shoots positively or negatively phototrophic?
Shoots are positively phototrophic as they grow towards the light
Are roots positively or negatively phototrophic?
Roots are negatively phototrophic as they grow away from the light
What is gravitropism?
The growth of a plant in response to gravity
Are shoots positively or negatively gravitropic?
They are negatively gravitropic as they grow upwards.
Are roots positively or negatively gravitropic?
Roots are positively gravitropic as they grown downwards
What are growth factors?
Hormone like chemicals that speed up or slow down plant growth
Where are growth factors produced?
In growing regions of the plant, e.g.. shoot and root tips
What are auxins and where are they produced?
Auxins are a type of growth factor that are produces In the tips of shoots.
Where of auxins go and what do they do?
Auxin diffuse backwards to stimulate the cell just behind the tips to elongate - this is where cell walls become loose and stretchy so the cell gets longer.
What happened if the tip of a shot is removed?
No auxin will be available and shoots stop growing
What happens if there are high concentrations of auxin?
It inhibits growth in roots
What is IAA?
Indoleacetic acid
An important auxin that produced in the the tips of shoots and roots in flowering plants
What is the function of IAA in plants?
It moves around the plant to control tropisms, which results in different parts of the plant having different concentrations of IAA, meaning theres an uneven distribution of IAA so there is uneven growth
How does IAA move around the plant?
- Over short distances it moves via diffusion and active transport
- Over long distances it moves via the phloem
