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Biology > M5 C16: Plant responses > Flashcards

M5 C16: Plant responses Flashcards

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1
Q

how can plants increase their chance of survival?

A

by responding to changes in the environment, abitoic stress and herbivory

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2
Q

what does abiotic stress mean?

A

a non living factor affecting an organism eg too much water, changes in light intensity or high temperatures

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3
Q

what does deciduous mean?

A

a tree that sheds its leaves annually.

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4
Q

why do deciduous trees lose their leaves?

A

the glucose needed to protect the plant from freezing is greater than the glucose produced in photosynthesis so the leaves are shed as the tree isn’t photosynthesizing
To conserve water and energy.
To prevent water in the leaves from freezing and rupturing them.
To allow wind to blow through the branches, reducing strain on the tree.

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5
Q

what does auxin do?

A

inhibits leaf loss. high in the summer
is produced by young leaves, when leaves is older it produces less
inhibits ethene

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6
Q

what does ethene do?

A

stimulates leaf loss, the older the leaf the more ethene it produces.

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7
Q

how does ethene stimulate leaf loss?

A

it causes the formation of abscission layer, by causing cells to expand and break. this stimulates production of enzyme cellulase which breaks down the cell wall.

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8
Q

how do some plants prevent freezing?

A

produce molecules that acts as an anti freeze by lowering the freezing point of cytoplasm eg sugars and polysaccharides

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9
Q

how does stomatal control act as a response to the environment?

A

open to cool plant down- water evaporates via transpiration
close to conserve water

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10
Q

what is ABA?

A

abscisic acid
is released when there is abiotic stress causing the closure
binds to receptors on guard cell membranes, causing ca2+ ions channels to open. k+ leaves the cell raising water potential causing water to leave the cell

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11
Q

what are some physical defences to herbivory?

A

cellulose cell wall- barrier, lignin in walls is also indigestible#
waxy cuticle- prevents water from collecting with pathogens need
guard cells- close stomata
callose- acts as a temporary wall when it becomes damaged

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12
Q

what are some chemical defenses to herbivory?

A

tannins- are toxic to microorganisms are bad tatsing
alkaloids- found in growing tips, tatse bitter
terpenoids- antibacterial properties and antifungal

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13
Q

what are pheromones?

A

are chemicals when released affect behaviour of others of same species

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14
Q

what are an example of pheromones?

A

maple trees release these when under attack so other maple trees absorb these and know to make more callose to protect themselves

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15
Q

what are volatile organic compounds?

A

organisms sends out signal to other organism such as an insect

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16
Q

what is an example of VOC’s?

A

when cabbages are attacked by caterpillars they produce a VOC which attracts a type of parasitic wasp that lays eggs inside the caterpillars eating them alive to stop them feeding off the cabbages

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17
Q

what is another physical defense?

A

folding in response to touch which dislodges insects and is thought to scare of larger organisms

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18
Q

what does tropism mean?

A

directional growth towards an external stimuli

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19
Q

what is a nastic response?

A

non directional response to an external stimuli

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20
Q

what is positive phototropism?

A

when shoots grow towards the light

21
Q

what is negative geotropism?

A

when shoots grow away from gravity

22
Q

what is positive what is positive geotropism?

A

when roots grow towards gravity

23
Q

how does phototropism work?

A

chemicals in the shaded side cause the plant to grow and bend towards the light

24
Q

what is chemotropism?

A

pollen tubes grow down the style towards the ovary where fertilisation happens

25
Q

what is thigmotropism?

A

where shoots wind around other plants or solid structures to gain support

26
Q

how do hormones work in plant responses?

A

they are produced by cells in a variety of tissues. they then reach the target cells and bind to receptors on the membrane

27
Q

what can hormones affect?

A

cell division, elongation, differentiation

28
Q

what does auxin do?

A

​Made in the tip of growing shoots and roots​
Unequally distributed in response to light or gravity​

29
Q

where will auxin be produced if the light source is directly above?

A

auxins produced at the tip are spread out evenly in the shoot so the entire shoot grows at the same rate, so the shoot grows straight up.

30
Q

where will the shoot grow if light is only present on one side?

A

There are more auxins on the shaded side of the shoot ​
The shaded side grows faster ( by cell elongation) making the bright side bend towards the light. ​

31
Q

what did boysen-jensen find in relation to phototropism?

A

sheet of mica on shaded side- no chemicals through do no bend
sheet of mica on light side- bend as chemicals in shaded side
gelatin through tip- curvature response as chem can go through

32
Q

what did darwin find in relation to phototropism?

A

cells in the tip cause phototropism, the plant to react to light

33
Q

what did went find in relation to phototropism?

A

chemicals diffuse from tips to agar which cause the plant to bend showing chemicals from the tip cause the plant to bend

34
Q

what effect does auxin have on roots?

A

auxin prevents the shoots from growing, it is produced at the bottom of the root due to gravity so the other side will grow and bend downwards

35
Q

what is apical and lateral budding?

A

The growth of the apical bud is dominant over the lateral bud

36
Q

how do auxins contribute to apical dominance?

A

If the shoot tip (apex) is cut, the plant grows from the lateral buds.​
Auxins from the apical bud prevent lateral buds from growing. ​
When the shoot is cut, auxin levels drop and the buds grow.

37
Q

what is the evidence to support apical dominance?

A

when a shoot is cut and a auxin paste is placed on it this stops lateral budding however when the shoot is covered with no paste the lateral buds do grow

38
Q

what are the other 2 hormones involved in plant growth?

A

abscisic acid: high auxin keeps abscisic high. When auxin is removed, abscisic levels drop and buds start to grow.​
Cytokinins: high levels of auxin cause cytokinins to move to the shoot apex. When apex is removed, cytokinin spreads evenly around the plant and causes bud growth.​

39
Q

what chemical is involved in ripening?

A

ethene helps ripen climacteric plants which continue to ripen after being harvested. ethene increases respiration. fruit is harvested before its ripe it is then exposed to ethene to ripen

40
Q

what are the advantages of transporting unripe fruit?

A

more hard so less easily damaged, less waste

41
Q

what chemicals are used in rooting powders?

A

auxin on cuts shoots stimulates root growth. this makes it easier to grow new plants from plant cutting. this can cause lots of new plants to grow from a few cells

42
Q

what chemicals are used in weed killers?

A

synthetic auxins act as a very effective weedkiller, they are applied to the weeds which increases the growth of them until they are unable to sustain the growth and then die

43
Q

what are the advantages of using weed killers?

A

they re cheap to produce, low toxicity, selective to certain plants

44
Q

what are other plant hormones used for?

A

auxins- production of seedless fruit
ethene- fruit dropping
cytokins- prevent aging
gibberelins- delay ripening

45
Q

what are gibberellins used for?

A

initiating seed germination, ending seed dormancy, promoting flowering and increasing fruit size

46
Q

how do gibberellins stimulate seed germination?

A

When the seed absorbs water, the embryo releases gibberellins which stimulates the production of amylase which breaks down starch into glucose ready for respiration.

47
Q

how do gibberellins stimulate growth?

A

Stimulates the stems of plants to grow by cell elongation so that they grow very tall.

48
Q

how is the relationship between auxin and gibberellins synergistic?

A

They can work together to make plants very tall

49
Q

how is the relationship between auxin and gibberellins antagonistic?

A

They can work against one another:​
Gibberellins promotes side shoots​
Auxin inhibits side shoots

Biology (15 decks)

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