Plant Hormones Flashcards
Auxin
Plant hormone which controls growth near tips of shoots and roots
Responds to phototropism, gravitropism and geotropism
Why do shoots grow towards light?
More auxin accumulates on side in shade
Makes cells elongate faster on shaded side
So shoot bends towards light
Why do shoots grow away from gravity?
Gravity produces unequal distribution of auxin in tip with more on lower side
Lower side grows faster
So shoot bends upwards
Why do roots grow towards gravity?
Root growing sideways with have more auxin on lower side
But on a root, extra auxin inhibits growth
Cells on top elongate faster
So root bends downwards
What method to investigate plant growth responses?
Using cress seeds under lamp
Control variables of this experiment
Same number of seeds in each dish
Use seeds that have all come from same packet
Stable temperature
Same amount of water
Same light intensity
Use of auxins commercially
Killing weeds
Growing from cuttings with rooting powder
Growing cells in tissue culture
Gibberellin
Stimulates plant stems to grow
Commercial uses of gibberellins
Controlling dormancy
Inducing flowering
Growing larger fruit
Ethene
Stimulates ripening of fruits
Commercial uses of ethene
Speed up ripening of fruit
Fruit can be picked whilst unripe and transported with ethene gas