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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
Q

How does nicotine kill insects?

A

by inhibiting nervous system function

- Low nicotine plants suffer more damage from herbivores

26
Q

What are the two signalling pathways that alert plants to damage from herbivores?

A

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
Q

What enables membrane signalling in plants to travel quickly

A

continuity of symplast

28
Q

What hormone can be released in response to damage from herbivores

A

Jasmonic acid (jasmonate)

29
Q

What does Jasmonate do?

A

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
Q

Why don’t defensive chemicals harm plants?

A

Compartmentalization
Toxin precursors stored separately to enzymes
Plant proteins do not react with toxins

31
Q

Explain how compartmentalization protects plants from defensive chemicals

A

Chemicals stored in vacuoles, dissolved in latex or dissolved in waxes on the epidermal surface

32
Q

Explain how Toxin precursurs are stored in different plces to protect plants from defensive chemicals

A

Toxin precursers an enzymes stored separately - come in contact when cell is ruptured

33
Q

How have beetles gotten around Milkweed’s stored defences?

A

Milkweeds store defensive chemicals in laticifers

One bug cut a few leaf veins then feed downstream to the leak

34
Q

What are potential environmental stresses a plant will face?

A 
Drought
Submersion
Heat
Cold
Salt
Heavy metals in soil
35
Q

How do have some plants adapted to dry conditions?

A 
Drought avoiders
Leaf adaptations
Root adaptations
Water storing structures
Solute accumulation
36
Q

What are drought avoiders?

A

Plants that carry out their lifecycle durign brief periods after rains
e.g. desert annuals

37
Q

Xerophytes are adapted to dry environment - what leaf adaptations do they have/

A

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
Q

How have cacti adapted to their environment?

A

spines instead of leaves - reflect solar radiation, dissipate heat and deter herbivores

39
Q

How are succulents adapted to dry environments?

A

Have fleshy water storing leaves or stems

- Have fewer stomata and variant form of photosynthesis

40
Q

How do roots adapt to dry environments?

A

cacti have shallow fibrous root systems that intercept water at soil surface

Tamarugo tree has deep taproot to reach groundwater

41
Q

How do plants in wet environments adapt?

A

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
Q

What are aerenchyma?

A

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
Q

Why is drought dangerous to plants?

A

Reduces membrane integrity - forces that orient lipid bilayer are reduced

  • protein 3D structure can change
  • Growth is reduced
44
Q

What is the first induced Responses to drought?

A

In roots abscisic acid is produced - moves to shoot and causes closure of stomata and initiates gene transcription for other responses

45
Q

What is the role of Late embryogenesis abundant (LEA) proteins in plant response to drought

A

upregulated due to change in gene transcription

- binds to other proteins to stabilize them and prevent clumping ith drying

46
Q

What is the danger of temperature extremes to plant?

A

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
Q

How have plants adapted to hot environments/

A

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
Q

What is cold hardening?

A

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
Q

What do ice crystals do to cells?

A

can puncture organelle and cell membranes

Draw water from cell and dehydrate them

50
Q

What are freeze tolerant plants?

A

plants with antifreeze proteins that slow the growth of ice crystals

51
Q

Why are saline environments hazardus to plants?

A

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
Q

What are Halpohytes?

A

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
Q

How do halophytes get rid of salt?

A

Salt glands that excrete salt

- is washed or blown away

54
Q

What are hyperaccumulators?

A

platns tolerant to heavy metals that are toxic to otehr plants
- They store large quantities of metals

55
Q

What are the adaptations of hyperaccumulators?

A
  • 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
Q

What is phytoremediation?

A

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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