Plant Hormones / Req Practical 8 Flashcards
Effect of gravity on seedlings
Shoots grow up against gravity, in the roots auxins accumulate on the lower side of the root encouraging growth downwards
Use clinostate, a device that continually rotates, this cancels out the effect of gravity, the shoots continue growing the way they were originally growing
As control set up a normal experiment without clinostate so the gravity force is still present, place 3 seedlings in a pot and leave for the same time u left the other leaves (1week).
Shoots grow up (positive phototropism/ negative gravitropism)
Roots grow down (negative phototropism / positive gravitropism)
Effect of light on seedlings (direction of light)
Add 10 seedlings to 3 separate cotton wool pads, place 1 in box with cut out on left, one with cutout on right, one with cutout on top. Leave for 1week and measure how the seedlings curve (they curve towards light source as they’re positively phototropic.
Controls:
Seedling type / Amount of water
Independent : direction of light
Dependant : mean curve of seedlings towards light source
Effect of light on seedlings (intensity)
Add 10 seedlings to 3 separate cotton wool pads, place 1 in bright light, one in reduced light, one in the dark. Leave for 1week and measure how much the seedlings grow by (mean).
They grew the fastest in the dark as they grow rapidly in order to grow out of the ground
Controls:
Seedling type / Amount of water
Independent : light intensity
Dependant : mean height of seedlings
Why do plants produce hormones?
Coordinate + control growth / responses to light (phototropism) / gravity (gravitropism)
Auxins
Cause growth in roots and shoots
Weed killers / rooting powder / promoting growth in tissue culture
Gibberellins
Initiating seed germination
Promotes flowering / end seed dormancy / increase fruit size
Ethene
Control cell division + cell ripening
Fruit industry = control ripening of fruit during transportation / storage
