Plant Hormones + RP Flashcards
Auxin
Plant hormone- controls growth near tips of shoots and roots
Growth in response to light (phototropism) and gravity (gravitropism/geotropism)
Moves backwards to stimulate cell elongation
If a tip is removed, no auxin, no growth
Auxin promotes shoot growth, inhibits in root
Shoots compared to light
When a shoot tip is exposed to light, more auxin in the shady section
Cells grow faster on shaded side, curve towards light
Shoots to gravity
When it grows sideways, gravity causes more auxin lower
Lower grows faster, bends shoot upwards
Root growing sideways has more low
In a root it inhibits growth, top elongates faster, bends downwards
RP
Ten cress seeds in 3 labelled Petri dishes
Shine lights, one above, one from each side
Leave for a week in the same conditions
See the response to light (grows towards)
Killing weeds.
Weeds are broad-leaves unlike grass
Selective weed killers developed with auxins to only affect broad leaves
Disrupt growth and kills them, wanted untouched
Rooting powder/ tissue culture
Cutting has a part cut off added to rooting powder with auxins, develops roots rapidly, making new parts from a small section
Tissue culture- take a few cells and add auxin to divide them and form roots and shoots
Gibberellin
Stimulates seed germination, stem growth, Flowering
Uses of gibberellin
Dormancy- seeds need certain conditions to germinate. Treated with gibberellin to alter conditions and make them germinate all year
Flowering- same as dormancy and makes bigger flowers
Larger fruit- makes seedless grow as large as seeded
Ethene
Gas produced by aging parts- influences growth by controlling cell division, also stimulates enzymes to ripen the fruit
Ethene uses
Speeds up ripening on plant or when transporting
Can be picked when unripe (firmer, harder to damage) and added on the way to the supermarket to ripen
Can be delayed until stored to add chemicals to block ethene’s effect or reduce it. Can also add chemicals which react with ethene
