Plant hormones (paper 2) TOPIC 5 Flashcards
what do plants need to grow well
- carbon dioxide
- sunlight
- water
- mineral ions
does the way a seed lands on the soil impact the growth
no
which way do roots grown
they grow down into the soil, anchoring the seedling and keeping it stable
why do roots grow down
because they are sensitive to gravity
what are plant growth responses called
tropsims
what are tropisms
tge responses if plant shoots and roots to light and gravity
what is phototropism
growth and responses to light
what is gravitropism/geotropism
growth reponses to gravity
what are the useful plant hormones
- auxin
- gibberellins
- ethene
what does unequal distributions of auxin cause
make one side of a shoot or root grow longer than the other, causing it to bend
what does auxin do
controls the direction of growth of root tips and shoot tips in response to different stimuli including light and gravity
where is auxin made
at the tips of stems and roots, diffusing along the shoot or roots
what will happen to auxin if light is coming in from one side
it will move to the opposite side of the shoot causing the cell to elongate on the one side and bend
what is the effect of high levels of auxin
it makes the shoot cells grow more but inhibit growth of root cells
does auxin move away or towards light
away
what effect does auxin have in the roots
the sides with less auxin will elongate faster
what effect does auxin have in the shoots
the sides with more auxin elongate faster
how do light and gravity interfer with the transport of auxin
they make it unevenly distributed
what is positive phototropism
when the stem tip grows towards light to get maximum light for photosynthesis
what is negative phototropism
when the root top grows away from light for less chance of drying out
what is positive gravitropism
when the root tip grows towards gravity for more chance of finding moisture
what is negative gravistropism
when the stem tip grows away from gravity for more chance of finding light
what else are plant growth hormones used in
- agriculture
- horticulture
how else is auxin used
- weed killer
- rooting powders
- growth in tissue culture
how is auxin used in weed killer
very high doses can cause plants to grow too quickly and die
how is auxin used as rooting powders
they encourage meristem in cuttings to grow new roots
explain how ethene is used in the food industry
to control ripening of fruit during storage and transport
- unripe fruit can be picked and transported
- the fruit can be ripened with ethene at its destination
what can gibberellins be used to do
- end seed dormancy
- promote flowering
- increase fruit size
what do gibberellins do in the plant
initiate seed germination
what does ethene do in the plant
controls cell division and ripening of fruits
