adaptations and hormones Flashcards
Describe the root system of a plant in the desert
Widespread, deep root system
Why do plants in the desert have longer roots?
To collect water from over a larger area
Why do plants in the desert have smaller leaves or spines?
Minimising surface area, reducing the number of stomata and therefore water loss. Spines might also protect from predators
Why do plants in the desert have thicker, waxy cuticles?
To reduce water loos by evaporation.
Why are there usually more stomata on the bottom of a leaf than on the top?
to reduce water loss by transpiration. The underside of a leaf is shaded from the sun and usually cooler.
How can you measure how many stomata are on a leaf?
make a layer of clear nail polish on the leaf and peel off onto a microscope slide. Use a microscope to count the number of stomata in a part of the leave. Work out the area you have sampled and the total area of the leaf. Then area of leaf / sampled area x number of stomata. Take repeat readings.
What is a phototropism
When a plant grows in response to light
What is the difference between a positive tropism and a negative tropism?
A positive tropism means the plant is growing towards a stimulus (e.g. light) whereas a negative tropism means the plant is growing away from the stimulus.
What is gravitropism?
A plant grows in response to gravity
Which part of the plant has a positive phototropism?
stem
Which part of the plant has a negative phototropism?
roots
What effect does auxin have on stems?
cells grow more
What effect does auxin have on roots?
cells grow less
How does auxin cause positive phototropism in shoots?
the sunlight breaks down auxin on the side of the shoot facing the sun. On the shaded side, the auxin causes the cells to elongate. The unequal growth on both sides of the shoot causes the shoot to bend towards the light.
Which part of a plant has a negative gravitropism?
Stems- they grow away from gravity
Which part of the plant has a positive gravitropism?
Roots- they grow towards gravity
How does auxin cause positive gravitropism in roots?
Gravity means the auxin gathers in the part of the root facing downward. Auxin slows the growth of these cells meaning the root curve downwards
What are some uses of auxins in agriculture?
Weed killers and rooting powders
What is the function of gibberellins?
causing seed germination and stimulating cell elongation
What are some uses of gibberellins in agriculture?
causing seeds to germinate at the correct time, making plants grow taller, making plants flower at a certain time and increasing fruit size. Giberellins are also used to produce seedless fruit.
What is the function of ethene in plants?
Causing fruit to ripen
What is a use for ethene in agriculture?
Causing fruit to ripen at a certain time, meaning it is fresh in shops
