coordination and response in plants Flashcards
(20 cards)
what is it called when a plant responds to light
phototrophism
how does the root respond to light
usually no response
-> however, if there is its called negative phototrophism
how do the shoot/stem/leaves respond to light
grow towards it
-> positive phototrophism
what is it called when a plant responds to gravity
geotrophism
how does the root respond to gravity
grows towards it
-> positive geotrophism
how do the shoot/stem/leaves respond to gravity
grow away from it
-> negative geotrophism
plants response to light if it is uniformed:
- auxin distributes evenly on each side of the shoot
- mitosis is stimulated evenly on each side
- cell elongation is the same
- plants grow upwards towards light
- more photosynthesis
place response to light if it is not uniformed (unidirectional):
- auxin accumulates on dark side (side not facing light)
- more mitosis/cell elongation on the dark side
- cells on dark side grow faster
- plant bends towards light
- more photosynthesis
clinostat practical:
- clinostat rotates
- means direction of gravity constantly changing
- means auxin doesn’t accumulate on one side
- means growth is even on both sides of root
- root grows straight out
control practical for clinostat:
- plasticine support stops clinostat rotating
- roots affected by gravity
- auxin accumulates on lower side of root, inhibiting growth
- roots bend down
what is auxin
a chemical/hormone that plants respond to
auxin:
- plants do not have a nervous system, so tropisms are caused by plant hormones
- the hormone responsible for the bending of shoots towards the light is called auxin
- the response to stimuli in the plants are controlled by chemical hormones
where is auxin made and how does it get to the area needed
made at the tip of the shoot and roots, it then diffuses down the stem to the region of growth
what does auxin change about the cells
changes their elasticity
what does auxin control and how
controls the growth of cells (called elongation) in the plants by increasing the growth in shoots of plants,and decreasing growth in the roots of plants
what does auxin stimulate in the growing region
mitosis
as well as causing individual cells to elongate
what do more elastic cells do
absorb more water and grow longer, causing bending in the stem or root
what does auxin do in roots (geotrophism)
INHIBITS growth
plants response to gravity:
- radicle (root) needs to grow down for water/minerals/anchorage
- plumule (shoot) needs to grow up towards sun for light for photosynthesis
- auxin accumulates on lower side of root and shoot
- auxin accumulates on lower side of roots, it inhibits growth on lower side of shoot (less mitosis)
- top side of shoot can still divide via mitosis and grow -> causes root to grow downwards into soil
- auxin accumulates on lower side of shoot -> more mitosis on lower side -> more cell growth
- causes shoot to bend upwards as lower side is growing faster
what does auxin do in shoot (geotropism)
STIMULATES growth
cress practical:
plants need to germinate:
- water -> soften testa causing it to split
-> activates enzymes -> seeds store starch - amylase and maltose break it down into glucose -> ungerminated seeds don’t store glucose
- oxygen -> respiration
- warmth -> optimum temp for enzymes
results of experiments:
1. covered with box and water
- would germinate
- would be tall and spindly -> growing upwards in search of light
- light and water
- control experiment - would germinate
- grow normally - dry
- wouldn’t germinate
- testa wouldn’t split -> enzymes not activated - box with hole on one side - some light and water
- would germinate
- bend towards light -> auxin accumulated on dark side - water in fridge
- wouldn’t germinate
- no warmth -> enzymes don’t have enough kinetic energy
