Plant responses

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What is tropism?
Directional growth in response to stimuli.
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What are the main types of tropism?
Phototropism, geotropsim, and hydrotropism
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What do these three stand for (In order)
Light, gravity, and water
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What is abiotic stress?
anything non-living which is harmful to the plant
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Give two examples of abiotic stress?
Drought, and extreme cold
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What are plants chemical defences?
Producing toxic chemicals when they are eaten
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What are three examples of a plants chemical defences?
Tannins - Bitter chemicals, Alakoids - Bitter tastes and poisonous characteristics, and Releasing pheromones to attract insects
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What are plant hormones (3 things)
Produced in small quantities, are active at the site of production and the effects are different dependant upon concentration
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What are meristems?
Groups of immature cells that are capable of dividing and sepcialising
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Where are apical meristems found?
Found at the tips or apex of roots and shoots,results in longer roots and shoots
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Where are lateral meristems found?
Found in a cylinder near the outside of roots and shoots cause them to widen
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Where are lateral bud meristems found?
Found in buds and could give rise to side shoots
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What does the effect of auxin have on the cell walls?
It elongates it
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How does auxin do this?
By promoting the active transport of H+ ions into the cell wall, decreasing the PH, leading to expansins breaking the gylcosidic bonds in the cell wall, whilst the influx of H+ ions breaks down hydrogen bonds, making the cell wall less rigid
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What does the plants cell do as a result of this?
Its decreased PH and breakdown of cross linkages means that the cell takes up water by osmosis, it swells and becomes larger
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What is gibberellin?
Plant hormone involved in growth and development, including stem elongation, flowering, and seed germination
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What do gibberellins do?
Gibberellins switch on the genes that produce amylase and proteases which begin to break down the cotyledons or endosperm (food stores) of the seed. • The embryo produces ATP from these food stores so it can begin to grow and break through the seed
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What is an antagonist of gibberellin?
ABA (absisic acid)
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What does ABA do?
•Binds to receptors on plasma membrane of stomatal guard cells • ABA activates changes in ionic concentration of guard cells • This affects water potential and therefore turgor of the cells
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What is a piece of experimental evidence for giberellin?
Pea plants that do not have the GA gene are short
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How does leaf abscission occur?
The thin absisiccion layer is weakened by enzymes that hydrolyse polysaccharides, so the leaf falls off and the tree grows a protective layer containing suberin where it has fell off
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What is apical dominance?
central stem of the plant is dominant over (i.e., grows more strongly than) other side stems
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How does apical dominance occur?
Auxin is produced in the apical meristem, and the presence of it in the lateral buds (side shoots) inhibits growth
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What is the evidence for apical dominance?
If a growing shoot is tipped upside down, side shoots will grow off and this is because auxin cannot travel upwards against gravity
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What are some commercial uses of plant hormones?
Auxin - Rooting powder to encourage root growth. Cytokinins - Delay leaf senescence. Giberellin aids in fruit production
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Other cards in this set

Card 2

Front

What are the main types of tropism?

Back

Phototropism, geotropsim, and hydrotropism

Card 3

Front

What do these three stand for (In order)

Back

Preview of the front of card 3

Card 4

Front

What is abiotic stress?

Back

Preview of the front of card 4

Card 5

Front

Give two examples of abiotic stress?

Back

Preview of the front of card 5
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