Plant Hormones Flashcards
(18 cards)
What is positive tropism
A plant grows towards a stimulus
What is negative tropism
A plant grows away from a stimulus
Phototropism involves
Light
Which plant organs undergo positive phototropism
Plant stem, leaves
Which plant organs undergo negative phototrpism
Plants roots
Auxins are hormones found in the meristem of plants, where are these found
- tips of roots and shoots
Stems and roots respond differently to high conc of auxins
- allows cells in the stem to grow more
- make cells in the roots grow less
What does geotropism involve
Gravity
Which plant organs undergo positive geotropism
- stem
Which plant organ undergoes negative geotropism
- roots
What are hormones
Chemical messangers
How to auxins cause stems to bend toward the sun
- There are more auxins found in the shaded part of the plant
- this allows the shaded part to grow more then the part of the plant exposed to the sun
- for the plant to stretch and grow towards light, the shaded part of the plant must be longer than the part exposed to light
- auxins allow this to happen
How do auxins make roots grow less
- auxins are still on the shaded side
- they allow that side of the roots to be shorter allowing the root to curve downwards and undergo positive geotropism
What happens is the tips of the plants aren’t expose to any light
- equal conc of auxin on both sides
What do gibberllin hormones do
initiate seed germination (growth)
- end seed dormancy
- promote flowering
- increase fruit size
Seed won’t start to grow until it has gibberellins
What is Ethene
- a hydrocarbon gas which speeds up the ripening in bananas and other fruits
How are auxins used
- as rooting powders to increase speed of growth
- for promoting growth in tissue culture
- as weed killers (too much auxins means too much growth that it can’t sustain itself)
What are selective weed killers
- contain lots of auxin
- caused the weeds to grow too quickly and die
