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Biology > PLANT RESPONSES > Flashcards

PLANT RESPONSES Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what do plant need to respond to?

A

abiotic factors
herbivore

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2
Q

how do plant respond to herbivores?

A

physical and chemical defences and touch responses

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3
Q

list chemical defences and what do they do

A

alkaloids - their toxicity leads to animal death so enables plants to survive and reproduce

pheromones- release of this alerts nearby plants to produce more callose or toxins to harden leaves and make difficult for animals to feed from them, increased survival

tannins - toxic to herbivores

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4
Q

what is meant with tropism?

A

organism response in a particular direction as a response to stimulus

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5
Q

positive tropic response?

A

toward stimulus

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6
Q

negative tropic response?

A

away from stimulus

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7
Q

types of tropisms and what are they?

A

phototropism - directional response to sunlight (positive for shoots negative for roots)

geotropism - directional response to gravity (positive for roots and negative for shoots)

chemotropism -a movement of organs in growth due to a chemical stimulus

thigmotropism - when a plant responds to a movement or touch from another stimulus

hydrotropism - the movement or growth of a plant towards water.

aerotropism - a behavioural response in a plant that results in it growing towards the presence of air.

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8
Q

what is a nastic movement?

A

is a reponse not affected by direction of stimulus

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9
Q

what are the plant growth regulators/factors?

A

enable plants to respond to stimuli

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10
Q

list the plant growth regulators

A

auxins
gibberellins
abscisic acid ABA
cytokinins
ethene

AGACE

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11
Q

explain what AUXIN does

A

promotes cell elongation in shoots allowing APICAL DOMINANCE

inhibits lateral buds growth

inhibits leaf fall

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12
Q

explain what GIBBERELLINS does

A

stimulate seed germination, flowering and stem growth

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13
Q

explain what ABSCISIC ACID (ABA) does

A

inhibits seed germination /growth

causes stomatal closure during stressful periods

inhibits lateral bud growth,so support apical dominance

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14
Q

explain what CYTOKININS does

A

stimulate cell division and differentiation
delay leaf senescence
promote cell expansion
overcomes apical dominance by promoting lateral buds growth

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15
Q

explain what ETHENE does

A

stimulates flowering and fruit ripening

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16
Q

factors that increase effect of growth

A

SYNERGIC

17
Q

factors that decrease effect of growth

A

ANTAGONISTIC

18
Q

what does apical meristems allow?

A

lenghtening

19
Q

what does lateral meristems allow?

A

widening

20
Q

by what does the plant growth rate depend?

A

concentration of growth factor
tissue being acted on
developmental stage
plant species

21
Q

explain the role of ethene and auxin in leaf loss

A

ethene- stimulates breakdown of cell wall in abscission layer, so leaf drop off

auxin - concentration of auxin decreases as the leaf ages

so as auxin level decreases, ethene level increases
disintegration of the abscission layer causes leaf to fall

22
Q

explain the role of ABSCISIC ACID (ABA) in stomatal closure

A

ABA binds to receptor on guard cells membrane, causing Ca2+ channels to open allowing Ca2+ influx , this causes K+ channels to opne and K+ to leave the guard cells

water potential inside the cell increases, water moves out, cell becomes flaccid and closes stomata

ABA reduces transpiration

23
Q

explain the role of GIBBERELLINS in seed germination

A

in right conditions, H2O absorption , germination occurs, embryo is stimulated, gibberellin is produced, gibberellin diffuses into the aleurone layer, this stimulates amylase synthesis , which hydrolyses starch into maltose,maltose is then rearranged into glucose and tranported to the embryo, which is used for respirarion, dormancy broken.

24
Q

what are the 2 other growth factors involved in apical dominance and lateral bud growth inhibition?

A

ABA and CYTOKININS
ABA - may inhibit lateral bud growth as increased concentration of auxin may keep increased concentration of ABA, so when apex is cut off, ABA concentration drops so lateral bud growth is promoted

CYTOKININS - promotes lateral bud growth
high levels of auxin in the shoot makes the apex a cytokinins sink produced in the roots, so when the shoot is cut off auxin and ABA level drop, allowing cytokinins to spread evenly around the plant, causing lateral bud growth

25
Q

what is the commercial use of auxin?

A

promotes flowering

root growth powder - encourages root growth

promotes seedless fruit growth

herbicide as too much shoot growthmakes the stem incapable of supporting itsel, dying

26
Q

what is the commercial use of cytokinins

A

prevent yellowing of lettuce leaves after being picked
help mass-produce plants
promotes bud shoot growth of small pieces of plants , to then being grown separately

27
Q

what is commercial use of gibberellins

A

delay senescense in citrus fruits,so can be left unpicked for longer so available for longer in shops

cytokinins+gibberelling allows apple shape elongation

allows grape stalk elongation so grape are less compacted so grow bigger

allows sugar cane stem elongation so more sugar can be stored

28
Q

what are the commercial uses of ethene

A

speed up fruit ripenng in apples, tomatoes and citrus fruit
fruit drop in cotton, cherry and walnut
female sex expression in cucumbers, so reduce chances of self-pollination

29
Q

what does IAA do and what is it?

A

type of auxin - stimulate cell elongation and division

Biology (18 decks)

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