topic 6 responses in plants and animals Flashcards
what is a tropism?
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
how do shoots respond to light?
positively phototropic- grow towards light
how do roots respond to light?
negatively phototropic- grow away from light
what is gravitropism?
growth of a plant in response to gravity
how do shoots respond to gravity?
negatively gravitropic- grow upwards
how do roots respond to gravity?
positively gravitropic- grow downwards
what is a growth factor?
hormone like chemical that speeds up/slows down plant growth
where are growth factors produced?
in the growing regions of the plant, move to where they are needed in other parts of the plant
what is auxin?
growth factor that stimulates the growth of shoots by cell elongation
what happens if the concentration of auxin is high?
can inhibit growth in roots
what is indoleacetic acid? (IAA)
auxin that is produced in the tips of shoots in flowering plants
how is indoleacetic acid moved around the plant?
by diffusion and active transport over short distances
via the phloem over long distances
what does uneven distribution of indoleacetic acid mean?
that there is uneven growth in the plant
what happens in phototropism? (IAA)
IAA moves to the shaded parts of shoots and roots, so there is uneven growth
what happens to IAA in the shoot during phototropism?
IAA concentration increases on the shaded side, cells elongate and the shoot bends towards the light
what happens to the IAA in the root during phototropism?
IAA concentration increases on the shaded side- growth is inhibited so the root bends away from the light
what happens to IAA during geotropism?
IAA moves to the underside of shoots and roots, so there is uneven growth
what happens to IAA concentration in the shoot during gravitropism?
IAA concentration increases on the lower side- cells elongate so the shoot grows upwards
what happens to the IAA concentration in the root during gravitropism?
IAA concentration increases on the lower side- growth is inhibited so the root grows downwards
what is a tactic response?
organisms move towards or away from a directional stimulus eg) light
what is a kinetic response?
organisms movement is affected by a non directional stimulus, eg humidity
what is a positive taxis?
when an organism moves towards a stimulus
what is a negative taxis?
when an organism moves away from a stimulus
