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19 Cards in this Set
- Front
- Back
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Pathogen |
A disease causing agent |
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Herbivore |
Animals or insects that eat plants |
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Induced Defenses |
Defenses triggered in response to a threat |
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Constitutive Defenses |
Defense that is always present |
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Three examples of physical/mechanical defenses are: |
Thorns, rhizomes, and the cuticle |
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Physical defenses are usually (induced or constitutive) |
Constitutive |
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How is the hypersensitive response initiated? |
First, the plant is attacked by a pathogen. Then, the pathogen's avr protein is recognised by the plant's R protein and binds! This activates the HR. |
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4 steps of the hypersensitive response |
1. Plant closes its stomata 2. Plant walls off infected area by strengthening the neighboring cell walls 3. Plant produces toxins (phytoalexins or ROI) which will harm the plant AND the pathogen 4. The SAR signal (salicylic acid) is spread throughout the plant. SAR promotes PR gene transcription which protects the plant from further infection. |
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Secondary metabolites |
Chemical defenses that (poison herbivores and) are produced by the plant but are not necessary for the plants survival/reproduction/etc. |
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Three types of secondary metabolites are: |
Phenolics, terpenes, and alkaloids |
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An example of a phenolic and its effects on an herbivore: |
Tannins, bind to digestive enzymes and make herbivore sick |
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An example of a terpene and its effects on an herbivore: |
Menthol, these volatile compounds repel insects and herbivores |
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An example of an alkaloid and its effects on an herbivore: |
Caffeine, nicotine; disrupts the herbivore's nervous system |
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What is systemin? |
A hormone produced after an attack by an herbivore |
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How does systemin work? |
Binds to receptors on undamaged cells and produces Jasmonic Acid. Jasmonic Acid then activates the transcription of proteinase inhibitors |
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Proteinase inhibitors |
Blocks enzymes that are responsible for digesting proteins in animals. Ingesting a large amount will make the animal sick. Plus! Animals will learn the taste of proteinase inhibitors and will avoid those plants in the future. |
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How does a plant recruit parasitoid wasps for indirect defense? |
1. Caterpillars attack plant 2. Plant releases volatile compounds to attract wasps 3. Wasps lay eggs in caterpillar, caterpillar dies!! |
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Another example of biotic defense? |
Acacia tree + ants + elephants |
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Why is investing in defense a trade-off? |
A plant can either grow or defend itself. It will be more likely to defend itself if it's in a favorable environment |
