Responses in Plants

Created by

Elizabeth Woolliscroft

Cards (10)

How to plants increase their chances of survival by responding to changes in their enviroment?
they sense the direction of the light and grow towards it to maximise light absorbtion
they can sense gravity, so their roos and shoots grow in the right direction
climbing plants have a sense of touch, so they can find things to climb and reach the sunlight
What are Auxins? 
plant growth hormones which control growth at the tips of shoots and roots.
how do auxins move through plants? 
in solution (dissolved in water)
Where is auxin produced? where does it go and why? 
in the tips
it diffuses backwards to simulate the cell elongation process which occurs in the cells just behind the tips
where does auxin promote and inhibit growth? 
promotes growth in the shoots
inhibits growth in the roots
which trophisms are auxins involved in? 
phototropism (growth responses to light)
geotropism (growth responses to gravity)
Shoots are Postively Phototrophic 
(grows towards light)
when a shoot tip is exposed to light it accumulates more auxin on the side that's in the shade than the side that's in the light
this makes the cells grow (elongate) faster on the shaded side, so the shoot bends toward sthe light
Shoots are Negatively Geotrophic 
(grow away from gravity)
when a shoot is growing sideways, gravity oroduces an unequal distribution of auxin in the tip, with more auxin on the lower side
this causes the lower side to grow faster bending, the shoot upwards
Roots are positively geotrophic  
(grow towards gravity)
a root growing sideways will also have more auxins on it lower side
but in a root the extra auxin inhibits growth, this means the cells on top elongate faster and the root bends downwards
Roots are negatively Phototophic 
if a root starts being exposed to some light, more auxin accumulates on the more shaded side
the auxin inhibits cell elongation on the shanded side so the root bend backwards into the ground.