Plant responses Flashcards
why do plants respond to light?
To maximise light absorption for photosynthesis
Why do plants respond to gravity?
So their roots and shoots grow in the right direction
How do climbing plants respond to changes in environment?
they have a sense of touch
- So they can find things to climb and move towards the sun light.
How do plants respond to herbivores?
By releasing toxic chemicals in response to being eaten
what are some examples of chemicals plants release in response to being eaten by herbivores?
Alkaloids- bitter taste, noxious smells, poisonous characteristics that deter or kill herbivores.
Tannins- bitter taste
- tannins can even bind to the proteins in the gut of the herbivore who ate the plant, making the plant hard to digest. Deter herbivores from eating.
What are pheromones that plants release?
Pheromones are signalling chemicals which produce a response in other organisms.
E.G: alarm pheromones are released into the air in response to herbivore grazing, This can cause nearby plants to detect these chemicals and start making chemical defences like tannins.
Why is plants folding a good way to respond to being touched?
Signal spreads throughout the leaf causing it to fold up. A leaf of the “mimosa pudica” plant does this.
This folding protects the plant as it helps to knock off small insects eating the plant or deter animals from eating the plant.
What is abiotic stress to a plant?
Anything that is harmful but NON living- like a drought or earthquake.
How do carrots respond to extreme cold?
Carrots produce anti freeze proteins, these proteins bind to ice crystals and lower the temperature at which the water freezes
What is a tropism?
The response of a plant to a directional stimulus.
positive tropism- grows towards stimulus
negative tropism- grows away from stimulus.
what is phototropism?
Growth of a plant in response to light
shoots are positively phototropic as they grow towards light
roots are negatively phototropic as they grow away from light
What is geotropism?
The growth of a plant in response to gravity
Roots are positively geotropic and grow downwards
Shoots are negatively geotropic and grow upwards.
What is thigmotropism?
Plant growth in response to object
What is thermotropism?
Plant growth in response to temperature.
What is hydrotropism?
Plant growth in response to water.
- Roots are positively hydrotropic
What are growth hormones in plants?
chemicals that speed up or slow down plant growth.
Where are growing hormones produced in a plant?
They are produced in the tips of shoots and leaves.
Which hormone promotes stem elongation auxins or gibberelins?
Gibberellins
what does the hormone gibberellin do?
They stimulate:
seed germination,
stem elongation
side shoot formation and flowering
What does the hormone auxin do?
Stimulates cell elongation ( growth of shoots)
cell elongation- is where the cell walls become loose and stretchy so the cells get longer.
What plant hormone in high concentration can inhibit growth in the roots?
Auxins
Is IAA auxin or gibberelin?
Auxin
(Indoleacetic acid)
It controls tropisms
and moves by diffusion and active transport over short distances
and moves via the phloem for long distances
What does uneven distribution of IAA mean
uneven growth of plant.
For phototropism how does IAA move?
Moves to the shaded parts of the shoots and roots, so there is uneven growth
shoots: IAA moves to the tip of the shoot, cells elongate and the shoot bends towards the light
Roots: IAA moves to the roots, growth is inhibited and root bends away from the light
For geotropism how does IAA move?
Moves to the underside of shoots and roots, so there is uneven growth.
shoots: IAA moves towards the underside of the shoot tip, cells elongate, so the shoot grows upwards.
roots: IAA moves towards the roots, growth is inhibited so the root grows downwards.
