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Biology module 5 > Plant Responses/hormones > Flashcards

Plant Responses/hormones Flashcards

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1
Q

What is it called when shoots bend towards light?

A

Positively phototropic

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2
Q

Why do plant shoots grow towards light?

A

To maximise photosynthesis

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3
Q

What do plants do to avoid competition?

A

Grow taller - outcompete other plants for light.

Deeper roots - absorb water and minerals where there is less competition.

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4
Q

What is allelopathy?

A

Interspecific effect when a plant releases chemicals that are leached into the soil to prevent the germination of seeds of other plants.

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5
Q

What is abiotic stress?

A

Anything non-living that can cause harm to a plant

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6
Q

How do tannins protect a plant?

A

In leaves - bitter tasting to stop animals eating it.

Toxic to insects - binds to digestive enzymes in saliva and inactivates them

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7
Q

How do alkaloids protect plants?

A

Very bitter tasting to stop animals eating it.

May act as drugs that affect the metabolism of animals - maybe poisoning them.

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8
Q

How do pheromones protect plants?

A

A chemical that is made by an organism which affects the social behaviour of other members of the same species.

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9
Q

What is a nastic response?

A

Fast, reversible movement and are non-directional

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10
Q

What is the name of a response to light?

A

Phototropism

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11
Q

What is the name of a response to water?

A

Hydrotropism

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12
Q

What is the name of a response to gravity?

A

Gravi/geo tropism

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13
Q

What is the name of a response to chemicals?

A

Chemitropism

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14
Q

What is the name of a response to touch?

A

Thigmo nasty

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15
Q

What is the name of a response to temperature?

A

Thermo tropism/nasty

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16
Q

What are tropisms?

A

Growth responses that act in a direction relative to a stimulus.

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17
Q

What is the basic mechanism for sudden leaf movement in Mimosa pudica?

A

Rapid loss of turgor pressure from the cells at the bases of the leaves and leaflets.

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18
Q

Why do roots want to grow downwards into soil?

A

Get to water and minerals for photosynthesis.

Anchorage in soil

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19
Q

What are hormones (in terms of plants)?

A

Chemical messengers that can be transported away from their site of manufacture to act in other parts of the plant (target cells)

20
Q

What are plant growth regulators?

A

Hormones that stay in the cells that make them and work there. (Not made by endocrine glands)

21
Q

How do hormones move in plants?

A

Active transport, diffusion or mass flow via phloem in sap or xylem vessels

22
Q

What is it called when hormones amplify each others effects?

A

Synergism

23
Q

What is it called when hormones cancel out each others effects?

A

Antagonism

24
Q

Where is auxin produced?

A

At the tip of the shoot and causes it to grow

25
Q

How does auxin produce cell elongation?

A

Auxin synthesised in meristem cells and diffuses away from tip.
Auxin binds to receptor sites which activates hydrogen ion pumps in cell surface membranes.
Low pH of cell walls keeps them flexible allowing the cells to expand as they absorb water.
Auxins destroyed by enzymes, cell walls become more rigid so no more cell elongation in possible.

26
Q

Which part of the plant cell provides mechanical strength?

A

Cellulose cell wall

27
Q

What does water increase the size of in cell elongation?

A

The large permanent vacuole

28
Q

What is the definition of tropism?

A

Plants response to a directional stimulus. Plants respond to the stimulus by regulating their growth.

29
Q

What is the definition of herbivory?

A

When plants are eaten by animals

30
Q

What is the definition of growth hormones?

A

Chemicals that slow down or speed up plant growth

31
Q

What is the definition of gibberellins?

A

Growth hormone produced in young leaves and in seeds. Stimulates seed germination, stem elongation, side shoot formation and flowering.

32
Q

What is the definition of auxin?

A

Stimulates the growth of shoots by cell elongation and inhibits growth of roots at high concentrations.

33
Q

What is the definition of Idoleacetic acid?

A

A type of auxin. Stimulates cell elongation of shoots and inhibits cell growth in roots

34
Q

How are seeds germinated?

A

Water is absorbed by the seed which stimulates gibberellins / GA.
Activates amylase in seed which breaks down starch to glucose. Glucose is then used in respiration to release energy which is then used to grow.

35
Q

How do you test for starch?

A

Iodine in solution goes from brown to blue/black

36
Q

How do you test for maltose?

A

Benedict’s solution.

Goes brick red (reducing sugar)

37
Q

What is the mechanism for stomatal closure?

A

Leaf cells produce abscisic acid (ABA) under abiotic stress.
ABA binds to receptors on the plasma membrane of stomatal guard cells.
Ions move out of the cell so water potential out of the cell drops.
Therefore, water moves out of the cell by osmosis, causing the stomata to close.

38
Q

What is senescence?

A

Ageing of deciduous leaves

39
Q

What is abscission?

A

Shedding of deciduous leaves

40
Q

Why do deciduous plants lose their leaves in autumn?

A

In temperate climates (not too extreme), they lose their leaves in autumn to reduce transpiration in winter when water can freeze in the soil.

41
Q

What happens to leaves during senescence?

A

They change colour as the chlorophyll breaks down

42
Q

What prevents leaf senescence?

A

Cytokinins, they maintain nutrient supply in leaves

43
Q

What happens before the leaves fall off?

A

A protective layer is formed to prevent the entry of pathogens.
Abscission layer is formed that will eventually break down to make the leaf fall off

44
Q

What happens to the abscission layer to make a leaf fall off?

A

the chemicals holding cells together are broken down. The petiole (leaf stalk) will break off at this point.

45
Q

What is apical dominance?

A

When the apical bud growing at the tip of a shoot produces auxin that inhibits the growth of lateral buds further down the shoot.
When the tip of the apical bud is cut, the lateral buds develop and side branches grow. The plant becomes bushy.

Biology module 5 (7 decks)

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