Plant Responses

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Why do plants need to respond to their environment?
Avoid abiotic stress and predation to survive long enough to reproduce.
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Define Tropism
Directional growth response in which direction of response is determined by direction of stimulus
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What is the role of auxins?
Promote cell elongation, inhibit side shoot growth/ leaf fall
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What is the role of Cytokinins?
Promote cell division
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What is the role of Gibberellins?
Promote seed germination and growth of stems
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What is the role of Abscisic acid?
Inhibit seed germination/ growth and stomatal closure if plant is stressed by low water availibility
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What is the role of Ethene?
Promotes fruit ripening
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What causes Phototropisms?
Shoots bend towards light source.Shaded side elongates faster. Auxins cause cell elongation and are broken down by enzymes. If illumination only from one side, auxins move down from tip to shaded side, not evenly, so elongation occurs
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Outline the role of hormones in leaf loss in deciduous plants
Cytokinin levels drop, source of nutrients dwindles. Auxin levels fall. Absciission zone now more sensitive to ethene and ethene produced> Enzyme cellulase then produced digesting walls of abscission zone
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What is Apical Dominance?
When apical bud at tip of shoot inhibits the growth of lateral buds further down the shoot
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How are Auxins used commercially?
1) Taking cuttings- Rooting powder. Dip end of cutting promotes growth. 2)Herbicides- Growth promoted to point where plant can't sustain and dies
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How are Gibberellins used commercially?
Delay ripening in fruit- left unpicked for longer and sold longer. Elongation of apples with cytokinins. Grapes can grow as less compact as stem grows
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How are Cytokinins used commercially?
Prevent lettuce yellowing- delay senescence. Used in tissue culture for mass production
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How is Ethene used commercially?
Speed up ripening, Promote fruit drop, prevent cucumber pollination (bitter), Promote lateral growth for flowering stems
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Card 2

Front

Define Tropism

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Directional growth response in which direction of response is determined by direction of stimulus

Card 3

Front

What is the role of auxins?

Back

Preview of the front of card 3

Card 4

Front

What is the role of Cytokinins?

Back

Preview of the front of card 4

Card 5

Front

What is the role of Gibberellins?

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