Chapter 40- Plant Defenses

Biology 106 with Miller/dodson at Saint Louis University

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By: Megan Elstun
Created: 2012-04-26
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2 types of stress

1. abiotic stress- caused by non-living factors (wind, temp)

2. biotic stress- caused by living factors (viruses, fungi, animals)

How do plants defend themselves against frost damage?

-ability to grow from axillary buds

-phenological traits are regulated by environmental cues

-phenology: naturally recurring events in organisms

-phenological traits:

-leaf flush (when leaves appear)

-flowering time

-fruit maturity

Climate and phenological traits

-evidence for warming climate comes from phenological traits

-timing of events is becoming earlier each year as climate warms

Biotic stress

threats caused by living organisms

-can tap into nutrient resources of plants or use their DNA-replicating mechanisms to self-replicate

-some kill plant cells immediately, leading to necrosis

Biotic stress: non-native species

-non-native species are the 2nd leading cause of extinction

-can out-compete native plant species

-have lack of predators in new environement

How do plants defend themselves against pests? (Physically)

physical barrier: dermal tissue system

-1st line of defense in all plants

-epidermal cells throughout the plant secrete wax to protect plant surfaces from water loss and attack

-above-ground parts are also covered with cutin

-silica inclusions, trichomes, bark, and thorns can offer protection

-suberin is found in cell walls of subterranean plant organs

How to plants defend themselves against pests? (Chemically)

-many plants produce toxins that kill herbivores, make them ill, or repel them with strong odors

-some are unique to plants

-some are found in plants and animals

-small cysteine-rich peptides with antimicrobial properties

-reveals ancient origin of innate immunity

-are secondary metabolites

Secondary metabolites

-metabolic pathways needed to sustain life are modified

-alkaloids:

-tannins

Secondary metabolites: Manihotoxin

-source: Cassava

-effect on humans: metabolized to release lethal cyanide

Secondary metabolites: Genistein

-source: soybean

-effect on humans: estrogen mimic

Secondary metabolites: Taxol

-source: Pacific yew

-effect on humans: anticancer drug

Secondary metabolites: Quinine

-source: Quinine bark

-effect on humans: antimalarial drug

Secondary metabolites: morphine

-source: Opium poppy

-effect on humans: narcotic pain killer

Allelopathic plants

-can poison other plants

-secrete chemicals into soil to block seed germination or inhibit growth of nearby plants

-minimizes competition for resources

-black walnut tree

How do plants protect themselves from their own toxins?

1. sequester a toxin in a membrane-bound structure

2. produce a compound that is not toxic until it is metabolized by attacking animal

Systemic/Induced defenses

-kick on once the plant has been attacked

-allows plant to conserve energy when it's not under attack

Systemin

-wound-response hormone produced by herbivore-damaged cells

1. cells damaged by insect attack produce systemin

2. systemin binds to receptors on membranes of undamaged cells

3. initiates synthesis of jasmonic acid in undamaged cells

4. jasmonic acid activates proteinase inhibitors that deter further attack by insects

Parasitoid wasps, caterpillars, and leaves

1. caterpillar eats leaf, a wound response in plant leads to release of a volatile compound

2. female parasitoid wasp is attracted

3. wasp lays fertilized eggs in caterpillar

4. eggs hatch and larvae kill caterpillar

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

-plants have a plant resistance gene (R); pathogens have an avirulence gene (avr)

-it is recognition of gene products (proteins) that is critical

-if binding occurs, plant can mount defenses that keep pathogen avirulent

-if no binding occurs, plant succumbs to disease

1. pathogen enters cell

2. proteins are released into cell by pathogen

3. R gene products from the plant cell bind to avr gene products

4. if binding occurs, R gene product is activated, triggering a protective hyper-sensitive response

About this deck

By: Megan Elstun
Created: 2012-04-26
Size: 19 flashcards
Views: 2

About StudyBlue

“Simply amazing. The flash cards are smooth, there are many different types of studying tools, and there is a great search engine. I praise you on the awesomeness.”
Dennis