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LIFE 103 > Plant Defenses > Flashcards

Plant Defenses Flashcards

1
Q

Factors that threaten plants

A

weather, fire, viruses, bacteria, fungi, animals, and other plants

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2
Q

What is the first line of defense in plants

A

dermal tissue system

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3
Q

Epidermal cells

A

Dermal tissue system

secrete wax to protect plant surfaces from water loss and attack

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4
Q

cutin

A

dermal tissue system

above-ground parts also covered with cutin

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5
Q

Suberin

A

dermal tissue system

Found in cell walls of subterranean plant organs

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6
Q

Other parts of the dermal tissue system

A

silica inclusions, trichomes, bark, and even thorns

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7
Q

what allows microbial entry

A

mechanical wounds

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8
Q

Parasitic nematodes

A

use their sharp mouth parts to get through the plant cell walls
Some form tumors on roots

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9
Q

what can increase the risk of frost damage

A

having bacteria on the leaf

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10
Q

How do fungi invade

A

seek out the weak spot in the dermal system, or stomata, to enter the plant

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11
Q

Phases of fungal invasion

A
  1. Windblown spore lands on leaves
  2. Spore germinates and forms adhesion pad
  3. Hyphae grow through the cell walls and press against cell membrane
  4. Hyphae differentiate into haustoria
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12
Q

Why are beetles dangerous

A

they transport fungi in their mouthparts

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13
Q

Blue stain fungi

A 
various species of fungi
Not closely related to eachother
Fungus in sapwood stops pitch flow - blocking tree from repelling beetles
Cuts water and nutrient flow
Fungus serves as food for larvae
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14
Q

Beneficial fungi and bacteria

A

Mycorrhizal fungi
Nitrogen-fixing bacteria like Rhizobium
Plant growth-promoting rhizobia (PGR

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15
Q

Plant growth-promoting rhizobia (PGR)

A

Bacteria provide substances that support plant growth

Can also limit the growth of pathogenic soil bacteria

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16
Q

Defensins

A

Chemical Defense
found in plants and animals
small, cysteine-rich peptides with antimicrobial properties
In some cases defenses limit protein synthesis

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17
Q

Secondary metabolites

A

Alkaloids and Tannins

18
Q

How can animals avoid the toxic effects of secondary metabolites

A

by eating a varied diet

19
Q

What is the effect of secondary metabolites

A

Metabolic pathways needed to sustain life are modified

20
Q

Types of secondary metabolites

A

Manihotoxin (cyanogenic glycoside), Genistein (phytoestrogen), Pacilitaxel (taxol, terpenoid)

21
Q

Types of alkaloids

A

Quinine, Morphine

22
Q

Two ways in which plants protect themselves from toxins

A
  1. Sequester a toxin in a membrane-bound structure
  2. Produce a compound that is not toxic until it is metabolized by attack animal
    - Cyanogenic glycosides break down into cyanide when ingested
23
Q

Allelopathic Plants

A

Secrete chemicals to block seed germination or inhibit growth of nearby plants
This strategy minimizes competition for resources
Very little vegetation grows under a black walnut tree

24
Q

How did socrates die

A

after drinking a hemlock extract containing nerve-paralyzing alkaloid

25
Q

How did Georgi Markov die

A

assassinated by KBG officers using ricin

A pinhead-sized metal sphere was injected from an umbrella tip into his thigh

26
Q

Ricin

A

Alkaloid produced by castor-bean plant (Ricinus communism)
6 times more lethal than cyanide and 2 times as cobra venom
A single seed can kill a small child
Functions as a ribosome-binding protein that inhibits translation

27
Q

Benefits of secondary metabolites to human health

A

Phytoestrogens of soy plants
Taxol of Pacific Yew Trees
Quinine of Cinchona trees

28
Q

Phytoestrogens of soy plants

A

appear to lower the rate of prostate cancer in Asian males
Questions have been raised about their effects on unborn babies
Babies consuming soy-based formula

29
Q

Taxol of Pacific Yew trees

A

fights cancers, especially breast cancer

30
Q

Quinine of Cinchona trees

A

effective against malaria, which is caused by four species of Plasmodium
Blocks DNA replication
Also leads to build-up of toxic hemes that poison the parasite

31
Q

Acacia trees and ants

A

small armies of ants protect Acacia trees from harmful herbivores
Plants provide ants with food and shelter

32
Q

Parasitoid wasps, caterpillars, and leaves

A

as caterpillar chews away, a wound response in the plant leads to release of a volatile compound
Female parasitoid wasp is attracted
Lays fertilized eggs in caterpillar
Eggs hatch and larvae kill caterpillar

33
Q

Systemic response to invaders

A

Static plant responses to threats have an energetic downslide
-are maintained in the presence or absence of threat
Energy resources would be conserved if the plant response was inducible
Defenses launched only when needed

34
Q

Wound response

A

Occurs when a leaf is chewed or injured
-one outcome leads to rapid production of proteinase inhibitors throughout the plant
Bind to digestive enzymes in the gut of the herbivore

35
Q

Signaling pathway of wound response involves

A

jasmonic acid
salicylic acid
Mechanical damage

36
Q

Wound response signaling

A
  1. Wounded leaves produce an 18-amino acid peptide called systemic
  2. Systemin moves throughout the plant in the phloem
  3. Cells with receptors produce jasmonic acid
  4. Jasmonic acid turns on genes for proteinase inhibitor
37
Q

H.H. Flor’s gene-for-gene hypothesis

A

Plants have a plant resistance gene (R); pathogens have an virulence gene (ave)
It is the recognition of the gene products that is critical
If binding occurs, plant can mount defenses that keep pathogen avirulent
If no binding occurs, the plant succumbs to disease

38
Q

Hypersensitive Response

A

Recognition of the pathogen by the R gene product leads to hypersensitive response
Leads to a very rapid cell death around the site of attack
Also to longer term, whole plant resistance

39
Q

Rapid cell death

A

due to hypersensitive response
Seals off the wounded tissue to prevent the pathogen or pest from moving into rest of the plant
Hydrogen peroxide and nitric oxide produced
-May signal cascade of chemical events resulting in localized host cell death

40
Q

Phytoalexins

A

antimicrobial chemical defense agents

41
Q

Systemic Acquired Resistance (SAR)

A

Systemic response by plants
Several pathways lead to broad-ranging resistance that lasts for a period of days
Long-distance inducer is likely salicylic acid
At the cellular level, jasmonic acid is involved in SAR signaling
SAR allows the plant to respond more quickly to a second attack

LIFE 103 (28 decks)

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