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Biological Systems > Chapter 28 Plants in the Environment > Flashcards

Chapter 28 Plants in the Environment Flashcards

1
Q

What pathogens affect plants?

A

fungi, bacteria, protists and viruses

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2
Q

What are the possible responses to pathogens from platns

A

Constitutive (always present)

Induced (produced in reaction presence of a pathogen)

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3
Q

What constitutive defences do plants have?

A

leaves and stems have cutin, suberin and waxes
Cells walls are barrer to pathogens

Some plants make chemicals that inhibit pathogens

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4
Q

What are elicitors?

A

molecules made by pathogens to trigger plant responses

  • peptides from bactera
  • fungal cell wall fragments
  • derived from plant cell walls broken down by pathogens
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5
Q

What is general immunity triggered by

A

elicitors called pathogen associated molecular patterns (PAMPS_

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6
Q

What are PAMPs usually?

A

molecules produced by enire classes of pathogens - such as flagellin or chitin in gungal cell walls

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7
Q

What is specific immunity triggered by?

A

specific elicitors called effectors

- Effectors bind to R receptors to trigger response

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8
Q

What are the responses that elicitors and receptors bonding might trigger

A
  • formation of NO and reactive oxygen species - toxic to some pathogens
  • Polymer deposition - lignin can block plasmodesmata to limit the ability of pathogens to spread
  • Hormone signalling
  • Change in gene expression - upregulation of pathogenesis-related genes and genes encoding antimicrobial phytoalexins
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9
Q

What are Pathogenesis related proteins

A

Some are enzymes that break down pathogen cell walls

Others are alarm signals to cells that have not been attacked yet

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10
Q

What is Gene-for-gene resistance

A

When plant has genes that code for receptor that recognises elicitor that is coded by the Avr gene in pathogens

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11
Q

What are avirulence genes?

A

Avr genes are pathogen genes that encode for elictors

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12
Q

What are Resistance genes

A

R genes encode for receptors specific to one or a few elicitors

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13
Q

What happens if plants do not have a receptor for an elicitor?

A

Pathogen is not recognized and pant is susceptibe to invasion

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14
Q

What is a major goal of plant breeders regarding immunity?

A

To identify R and Avr genes and breed new R genes into crops to incrase pathogen resistance

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15
Q

What is the hypersensitive response in plants?

A

When cells around infection undergo apoptosis to prevent spread of pathogen - some produce phytoalexins that trigger surrounding cells to produce lignin to seal of plasmodesmata

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16
Q

What is systemic acquired immunity?

A

general increase in resistance of an entire plant to a range of pathogens
- Effect may last a growing season

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17
Q

What initiates systemic acquired immunity?

A

salicylic acid - which is produced in general and specific immunity
Is a signal to turn on other responses

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18
Q

How is Salicylic acid transported

A

In plant - to trigger production of PR proteins

Methyl salicylate is volatile and travels througgh the air. Can trigger production of PR proteins in neighbouring plants

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19
Q

How does systemic acquired resistance against RNA work?

A

Plants enzymes convert single stranded virus RNA into double stranded RNA and chop it into small interfering RNAs (siRNAs)

  • siRNAs help degrade vial mRNAs - blocking replication
  • siRNAs spread by plasmodesmata - providing systemic resistance
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20
Q

What is the most common herbivore?

A

Insects

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21
Q

What constitutive defences do plants have against herbivores?

A

Physical features - trichomes, thorns, spines, thick cell walls, tree bark

Some have insoluble salt crystals that damage insect cells?

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22
Q

What is the role of calcium oxalate in protecting plants from herbivores?

A

Insoluble salt crystal that damages insect tissues

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23
Q

What chemical defences to plants have against herbivores?

A

Secondary metabolites (not used for basic cell metabolism) that have a variety of actions

24
Q

What is Canavanine

A

Secondary metabolite - amino acid similar to arginine

  • Incorporated into insects proteins where arganine should be and changes tertiary structure
  • leads to abnormalities that kill insect
25
How does nicotine kill insects?
by inhibiting nervous system function | - Low nicotine plants suffer more damage from herbivores
26
What are the two signalling pathways that alert plants to damage from herbivores?
Membrane signalling - electric potential changes occur in damage area - signal travels over most of plant in 10 minutes Chemical signalling - chemicals in insect saliva combine with fatty acids to form elicitors
27
What enables membrane signalling in plants to travel quickly
continuity of symplast
28
What hormone can be released in response to damage from herbivores
Jasmonic acid (jasmonate)
29
What does Jasmonate do?
triggers many defences including synthesis of protease inhibitors Inhibitors interfere with digestion of proteins in insect gut and shunt growth - Also attracts insects that prey on herbivores
30
Why don't defensive chemicals harm plants?
Compartmentalization Toxin precursors stored separately to enzymes Plant proteins do not react with toxins
31
Explain how compartmentalization protects plants from defensive chemicals
Chemicals stored in vacuoles, dissolved in latex or dissolved in waxes on the epidermal surface
32
Explain how Toxin precursurs are stored in different plces to protect plants from defensive chemicals
Toxin precursers an enzymes stored separately - come in contact when cell is ruptured
33
How have beetles gotten around Milkweed's stored defences?
Milkweeds store defensive chemicals in laticifers | One bug cut a few leaf veins then feed downstream to the leak
34
What are potential environmental stresses a plant will face?
``` Drought Submersion Heat Cold Salt Heavy metals in soil ```
35
How do have some plants adapted to dry conditions?
``` Drought avoiders Leaf adaptations Root adaptations Water storing structures Solute accumulation ```
36
What are drought avoiders?
Plants that carry out their lifecycle durign brief periods after rains e.g. desert annuals
37
Xerophytes are adapted to dry environment - what leaf adaptations do they have/
Thick cuticiles and many trichomes to retard water loss Trichomes that diffract and diffuse sunlight to decrease risk of damage by high light intensity - Some have sunken stomata (protect from drying air currents) - Some accumulate solutes to lower water potential
38
How have cacti adapted to their environment?
spines instead of leaves - reflect solar radiation, dissipate heat and deter herbivores
39
How are succulents adapted to dry environments?
Have fleshy water storing leaves or stems | - Have fewer stomata and variant form of photosynthesis
40
How do roots adapt to dry environments?
cacti have shallow fibrous root systems that intercept water at soil surface Tamarugo tree has deep taproot to reach groundwater
41
How do plants in wet environments adapt?
Shallow root systems (O2 more likely to be near surface) | Mangroves have pneumatophores: root extensions that grow p out of water that have lenticels (openings) to let air in
42
What are aerenchyma?
large air spaes in leaf and stem parenchyma and petioles of submerged aquatic plants - Store O2 produced by photosynthesis - Imparts buoyancy - decreases number of cells, reduces metabolism
43
Why is drought dangerous to plants?
Reduces membrane integrity - forces that orient lipid bilayer are reduced - protein 3D structure can change - Growth is reduced
44
What is the first induced Responses to drought?
In roots abscisic acid is produced - moves to shoot and causes closure of stomata and initiates gene transcription for other responses
45
What is the role of Late embryogenesis abundant (LEA) proteins in plant response to drought
upregulated due to change in gene transcription | - binds to other proteins to stabilize them and prevent clumping ith drying
46
What is the danger of temperature extremes to plant?
High temp - destabilizes membranes and denatures proteins (especially enzymes of photosynthesis) Low - causes loss of membrane fluidity and permeability Freezin - causes ice crystals to form, damaging membranes
47
How have plants adapted to hot environments/
similar to xerophytes - hair and spines dissipate heat and leaf forms that intercept less sunlight Heat shock response - heat shock response made in response to abscisic acid
48
What is cold hardening?
acclimation by exposure to cooler temperatures over many days - Increase in unsaturated fatty acids to maintain cell membrane fluidity - Proteins similar to LEA protect against chilling injury
49
What do ice crystals do to cells?
can puncture organelle and cell membranes | Draw water from cell and dehydrate them
50
What are freeze tolerant plants?
plants with antifreeze proteins that slow the growth of ice crystals
51
Why are saline environments hazardus to plants?
Saline environment have negative water potential - water diffuses out of the cell Also sodium ions can be toxic as they inhibit enzymes and protein synthesis
52
What are Halpohytes?
plants adapted to saline environments - Take up Na and Cl into roots and transpor them to central vacuoles of leaf cells - Makes water potential negative
53
How do halophytes get rid of salt?
Salt glands that excrete salt | - is washed or blown away
54
What are hyperaccumulators?
platns tolerant to heavy metals that are toxic to otehr plants - They store large quantities of metals
55
What are the adaptations of hyperaccumulators?
- Increased ion transport into the roots - increased rate of translocation of ions to the leaves - Accumulation of ions in vacuoles in the shoot - Resistance to the ion's toxicity
56
What is phytoremediation?
form of bioremediation using plants to clean up pollution in soils - Hyperaccumulaters are planted and then harvested and disposed of to remove contaminatns

Biological Systems (20 decks)

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