Plant responses

?
  • Created by: ElishaG
  • Created on: 07-01-18 21:37
How do plants react to a change in their environment ?
1)Dropping leaves in autumn. 2)Seeds germinating in spring.3)Roots growing towards moisture.4)Shoots growing towards sunlight.5)Stomata closing under water stress.
1 of 54
Explain why plants need to be able to respond to their environment.
1)To cope with changing conditions.2)Avoid abiotic stress.3)To maximise photosynthesis.4)Avoid herbivory.5)To ensure germination in suitable conditions.6)Pollination
2 of 54
What is herbivory?
The eating of plants by herbivores.
3 of 54
What is a physical response to herbivory?
Folding in response to touch.
4 of 54
Describe folding in response to touch.
Most move slowly-can only see on time lapse.Mimosa pedica moves at a visible speed.If leaves are touched,they fold and collapse to dislodge insects-recover after 10-12 mins.
5 of 54
What are chemical responses to herbivory?
1)Tannins.2)Alkaloids.3)Terpenoids.4)Pheremones.
6 of 54
Describe tannins.
Bitter taste- puts animals off eating.Toxic to insects-bind to digestive enzymes and inactivate them.Tea and red wine are rich in tannins.
7 of 54
Describe alkaloids.
Bitter- act as drugs affecting metabolism, may poison them. Include nicotine, caffeine,morphine and cocaine.Caffiene toxic to insects and fungi. Caffeine in coffee bush spreads through soil and prevent germination
8 of 54
Describe terpenoids.
Act as toxins to insects and fungi. pyrethrin is produced by chrysanthemums and act as neurotoxin. Act as insect repellents, e.g. Citronella.
9 of 54
Describe Pheremones.
Chemical made by organism which affects Social behaviour of other membranes of same species. Help the to defend themselves.
10 of 54
What is tropism?
A directional growth response of a plant in which direction of response is determined by direction of external stimulus. Positive tropism= towards stimulus. Negative tropism= away from stimulus.
11 of 54
What is phototropism?
Stimulus= light. Advantage= ensures photosynthesis regions get access to as much light as possible.
12 of 54
What is geotrophism?
Stimulus= gravity. Advantage= shoots show negative geotrophism and roots show positive geotrophism.
13 of 54
What is hydrotropism?
Stimulus= moisture. Advantages= increases access of roots to water.
14 of 54
What is thigmotropism?
Stimulus= touch. Advantages= allows climbing plants to detect and curl around support.
15 of 54
What is chemotrophism?
Stimulus=chemicals. Advantages= depends on chemical
16 of 54
What are nastic responses?
A non-directional growth response of a plant.
17 of 54
Name a plant growth regulator?
Auxin.
18 of 54
Where is auxin produced?
Apical meristem at shoot tip and root tip. Move from cell to cell by diffusion and active transport. Transported around plant with xylem ans phloem by mass flow.
19 of 54
What are actions of auxin?
Cell elongation. Apical dominance.
20 of 54
Describe the mechanism of auxin.
Promotes the active transport of H+. Lowers PH. Optimum conditions for enzymes expansins. Expansins break bonds in cellulose.Walls less rigid. Walls can expand. Auxin loosens cellulose fibres in wall allowing to bend towards light.
21 of 54
Which side of a plant would cells elongate the fastest?
Shaded
22 of 54
Where would the highest concentration of auxins be?
Shaded apical shoot.
23 of 54
What is an advantage of higher concentration of auxin here?
Promotes cells to elongate and expand here which causes the bend towards the light.
24 of 54
What did Darwin and Darwins auxin experiments tell us?
Indicates tip responds to light as there is no response when tip is removed or covered. But is a response with intact tip.
25 of 54
What did Boysen-Jensons experiments show?
Indicated signal produced in tip and diffuses down stem as when tip is cut and replaced with gelatine block response seen. Mica block- no response.
26 of 54
What is geotrophism?
A plant response to gravity.
27 of 54
Why is it advantageous for roots to grow towards gravity?
Shoots show negative geotrophism, roots show positive. Advantageous for roots to grow towards gravity as they're responsible for absorption of H2O and minerals in soil.
28 of 54
What is apical dominance?
Inhibition of lateral shoot growth by auxins.
29 of 54
What is the effect if apical dominance on a plant?
Plant grows tall and thin with no lateral shoots.
30 of 54
What is apical dominance inhibited by?
Absence of auxins.
31 of 54
Describe what happens when apical bud is present
Apex and apical meristem intact so auxins present.Plant tall and thin. Lateral shoots not developed.
32 of 54
Describe what happens when apical bud is removed.
Apex and apical meristem removed so auxins absent. Plant short and bushy, lateral shoots developed.
33 of 54
What is gibberellin?
Role in cell elongation. Stimulates cell division and elongation by switching on certain genes.
34 of 54
Where is gibberellin produced?
Internode sections.
35 of 54
Describe the actions of gibberellins
Seed germination and stem elongation
36 of 54
Describe seed germination for gibberellin.
Water enters seeds by osmosis. Mobilises gibberellins. Gibberellins promote production and activity of amylase. Causes breakdown of starch into maltose and then glucose which can then be used in respiration to produce ATP.
37 of 54
Describe stem elongation for gibberellin.
Causes active transport of H+ ions into tissues. Decreases PH providing optimum conditions for expansin enzymes. Expansins loosen the cellulose cell wall making it less rigid and allowing cell expansion. Also cause growth by mitosis.
38 of 54
Summarise auxin.
Causes stem elongation. Create accidic environment by causing the active transport of H+ ions promoting activity of expansin enzymes.Causes cell elongation. No cell division. Loosen cell walls.Causes cell growth behind shoot.
39 of 54
Summarise Gibberellins.
Causes stem elongation. Create accidic environment by causing active transport of H+ into tissues- promotes activity of expansin enzymes. Causes cell elongation. Causes cell division.loosen cell walls. Causes cell growth in internodes.
40 of 54
What is the advantage of stomata usually being open during day and closed at night.
Open during day to allow gas exchange. Close during night to conserve water when there's no light for photosynthesis.
41 of 54
What plant hormone has role in closure of stomata?
ABA (Abscisic acid).
42 of 54
Describe stomatal closure.
1)ABA binds to receptors on cell surface membrane of guard cells.2)A complex series of events occurs, which occurs in opening of Ca2+ channels causing Ca2+ to enter. PH increases.K+, NO3- and Cl- to leave cell. The wp increases, w out by osmosis.
43 of 54
Stomatal closure continued.
The cells lose turgor which closes stomata.
44 of 54
What is leaf abscisison?
Leaf fall, occurs in autumn/winter in response to Lower temperatures and shorter days. Photosynthesis limited so leaf fall reduces water loss via transpiration.
45 of 54
What is leaf abscission inhibited by?
Cytokinins and auxins.
46 of 54
What is the mechanism of leaf abscission?
Acts on cells in abscisison zone. Reducing sensitivity to ethene.
47 of 54
Describe the cytokinins in leaf abscission.
Prevent senescence by ensuring leaf acts as a sink in translocation. Ensures adequate supply of nutrients. Cytokinin production decreases during autumn/winter.
48 of 54
Describe the senescence in leaf abscisison.
Leaf ageing/dying.
49 of 54
Describe the auxins in leaf abscisison.
Presence of auxins inhibits production of ethene. The decrease in cytokinin production causes a decrease in auxin production. With no auxin to inhibit it, ethene production increases
50 of 54
Describe ethene in leaf abscisison.
Promotes the production and activity of cellulose enzymes, these breakdown the cellulose cell walls of cells in abscisison zone without this support cells die and leaf breaks off.
51 of 54
Describe seed germination.
1)Seed absorbs water.2)Seed is activated and begins to produce gibberellins.3)Turn into stimulate production of enzymes that break down food stores.The embryo plant uses food stores to produce ATP for building materials so it can grow.
52 of 54
Seed germination continued.
And break through the seed coat. 5) evidence suggests that gibberellins swtichon genes that code for amylase and proteases.
53 of 54
What are the top 4 commercial uses for plant growth regulators?
1)Rooting powders.2)Tissue culture. 3)Fruit ripening. 4)Herbicide.
54 of 54

Other cards in this set

Card 2

Front

Explain why plants need to be able to respond to their environment.

Back

1)To cope with changing conditions.2)Avoid abiotic stress.3)To maximise photosynthesis.4)Avoid herbivory.5)To ensure germination in suitable conditions.6)Pollination

Card 3

Front

What is herbivory?

Back

Preview of the front of card 3

Card 4

Front

What is a physical response to herbivory?

Back

Preview of the front of card 4

Card 5

Front

Describe folding in response to touch.

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Cellular processes resources »