Plants - B1a Flashcards
What is auxin?
Is a plant hormone that controls growth near the tips of roots and shoots in plants.
What does auxin respond to?
Light, (phototropism)
Gravity (gravitropism or geotropism)
Moisture
What is the effect of extra auxin?
Promotes growth in the shoots but inhibits growth in the roots.
How does auxin work?
It is produced in the tips and moves backwards to simulate cell elongation. If the tip is removed,no auxin is available so the plant stops growing.
Explain what happens with auxin in shoots in response to LIGHT
When the shoot tip is exposed to light, more auxin accumulates on the shaded side. This makes the cell elongate faster on the shaded side and bend towards the light.
Explain what happens with auxin in shoots in response to GRAVITY
When a shoot is growing sideways gravity produces an unequal distribution of auxin in the tip, so more auxin is on the lower side. This causes it to grow faster and bend upwards.
Explain what happens with auxin in roots in response to GRAVITY
A root growing sideways will have more auxin on the lower side. But in a root extra auxin inhibits growth. So the top of the cell will elongate faster and the root bends downwards.
Explain what happens with auxin in roots in response to MOISTURE
Uneven amounts of moisture either side of the root produces more auxin on the side with the most moisture. This inhibits growth on that side causing the root to bend in that direction, towards moisture.
How are plant hormones used in agriculture?
Some plant hormones make weed killers to kill only the weeds in gardens that farmers don’t want. They disrupt their normal growth pattern, kill them but don’t harm crops.
Plant cuttings have root powder added to them which contains plant hormones. This helps them to produce roots quickly and grow as a healthy plant and farmers can produce clones easily.
