y11 test1 Flashcards
What are plants sensitive too?
light
gravity
temperature
water
physical touch
What is a tropism
A directed growth response
What is positive phototropism
towards light
What is positive geotropism
towards gravity
What is positive hydrotropism
towards water
What is positive thigmotropism
towards touch
Where is auxin produced
At the base of the tip of the plant
What happens when light is shone directly above a plant?
Because the light is coming from straight above, there is even distribution of auxin on both sides of the shoot, causing equal growth and elongation on both sides, so the plant grows upwards
Explain positive phototropism
Auxin is produced at the base of the tip. As light is shining from the side, more auxin diffuses down the shaded side of the shoot. Therefore, there is uneven distribution of auxin on both sides of the shoot, which causes unequal growth and elongation of cells on the shaded side of the shoot. Therefore, the plant grows towards the shoot
What is auxin
a plant hormone. it causes cell division and elongation in the shoots. it inhibits cell division and elongation in the roots
(required practical- investigate the effect of light on the growth of newly germinated chess seeds) what equipment is used?
petri dish
filter paper
measuring cyclinder
cress seeds
tweezers
scissors
cardboard box
(required practical- investigate the effect of light on the growth of newly germinated chess seeds) what are the control variables?
number of seeds
type of seeds
temperature
light intensity
time to grow
amount of water
(co2 concentration)
(humidity)
(required practical- investigate the effect of light on the growth of newly germinated chess seeds) what would you expect as the results?
full light- grows upwards
partial light- positive phototropism
darkness- upwards very quickly then dies (reaching for the light)
Explain positive geotropism in the roots
auxin is made at the base of the tip
when a root lays sideways, gravity causes unequal distribution of auxin, which accumulates on the lower side
In the roots, auxin inhibits growth and elongation
the upper surface of the root grows faster than the lower surface, so the root grows downwards
Explain negative geotropism
auxin is made at the base of the tip
when a shoot lays sideways, gravity causes unequal distribution of auxin which accumulates in the lower surface
in the shoots, auxin promotes growth and elongation
the lower surface of the shoot grows fast, so the shoot bends upwards away from gravity
