Plant Defenses

Question 1

Factors that threaten plants

Answer 1

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

Question 2

What is the first line of defense in plants

Answer 2

dermal tissue system

Question 3

Epidermal cells

Answer 3

Dermal tissue system

secrete wax to protect plant surfaces from water loss and attack

Question 4

cutin

Answer 4

dermal tissue system

above-ground parts also covered with cutin

Question 5

Suberin

Answer 5

dermal tissue system

Found in cell walls of subterranean plant organs

Question 6

Other parts of the dermal tissue system

Answer 6

silica inclusions, trichomes, bark, and even thorns

Question 7

what allows microbial entry

Answer 7

mechanical wounds

Question 8

Parasitic nematodes

Answer 8

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

Question 9

what can increase the risk of frost damage

Answer 9

having bacteria on the leaf

Question 10

How do fungi invade

Answer 10

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

Question 11

Phases of fungal invasion

Answer 11

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

Question 12

Why are beetles dangerous

Answer 12

they transport fungi in their mouthparts

Question 13

Blue stain fungi

Answer 13

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

Question 14

Beneficial fungi and bacteria

Answer 14

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

Question 15

Plant growth-promoting rhizobia (PGR)

Answer 15

Bacteria provide substances that support plant growth

Can also limit the growth of pathogenic soil bacteria

Question 16

Defensins

Answer 16

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

Question 17

Secondary metabolites

Answer 17

Alkaloids and Tannins

Question 18

How can animals avoid the toxic effects of secondary metabolites

Answer 18

by eating a varied diet

Question 19

What is the effect of secondary metabolites

Answer 19

Metabolic pathways needed to sustain life are modified

Question 20

Types of secondary metabolites

Answer 20

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

Question 21

Types of alkaloids

Answer 21

Quinine, Morphine

Question 22

Two ways in which plants protect themselves from toxins

Answer 22

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

Question 23

Allelopathic Plants

Answer 23

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

Question 24

How did socrates die

Answer 24

after drinking a hemlock extract containing nerve-paralyzing alkaloid

Question 25

How did Georgi Markov die

Answer 25

assassinated by KBG officers using ricin | A pinhead-sized metal sphere was injected from an umbrella tip into his thigh

Question 26

Ricin

Answer 26

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

Question 27

Benefits of secondary metabolites to human health

Answer 27

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

Question 28

Phytoestrogens of soy plants

Answer 28

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

Question 29

Taxol of Pacific Yew trees

Answer 29

fights cancers, especially breast cancer

Question 30

Quinine of Cinchona trees

Answer 30

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

Question 31

Acacia trees and ants

Answer 31

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

Question 32

Parasitoid wasps, caterpillars, and leaves

Answer 32

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

Question 33

Systemic response to invaders

Answer 33

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

Question 34

Wound response

Answer 34

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

Question 35

Signaling pathway of wound response involves

Answer 35

jasmonic acid salicylic acid Mechanical damage

Question 36

Wound response signaling

Answer 36

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

Question 37

H.H. Flor's gene-for-gene hypothesis

Answer 37

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

Question 38

Hypersensitive Response

Answer 38

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

Question 39

Rapid cell death

Answer 39

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

Question 40

Phytoalexins

Answer 40

antimicrobial chemical defense agents

Question 41

Systemic Acquired Resistance (SAR)

Answer 41

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