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What are auxin?
Auxins are plant hormones which control growth at the tips of roots and shoots
Auxin is produced in the tips and diffuses backwards to stimulate the cell elongation process
Auxin promotes growth in the shoot, but actually inhibits growth in the root
What does positively phototrophic mean?
When a shoot tip is exposed to light, it accumulates more auxin on the side that’s in the shade than the side thats in the light
This makes the cell grow faster on the shaded side, so the shoot bends towards the light
What does negatively geotropic mean?
When a shoot is growing sideways, gravity produces 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
What does positively geotropic mean?
A root growing sideways will also have more auxin on its lower side
But in a root the extra auxin inhibits growth. This means the cells on top elongate faster, and the root bends downwards
What does negatively phototrophic mean?
If a root stars being exposed to some light, more auxin accumulates on the more shaded side
The auxin inhibits cell elongation on the shaded side, so the root bends downwards, back info the ground
What is a clinostat?
A device which uses rotation to negate the effects of gravitational pull on plant growth and development
