Plant Survival and Defense Flashcards
Survival techniques for evolution of photosynthesizing land plants had to adapt to life outside of water
- growth above ground
- reduction of desiccation
- strategies for dispersal and pollination
- chemical communication between plants
- strategies for defense
growth above ground
- xylem and phloem for water and food transfer
- lignin and bark give strength and rigidity to cells
reduction of desiccation
- waxy cuticle
- stomata regulate gas exchange and water retention
- sporopollenin and seeds protect reproductive structures
strategies for dispersal and pollination
- birds, insects, and animals
chemical communication between plants
- Occurs as cooperative warning system as well as a way to deter
competitors from invading space
strategies for defense
mechanical and chemical strategies to reduce herbivory
Mechanical Strategies
- waxy cuticle
- tough leaves
- physical defenses
- mimicry
What is Convergent Evolution
- similar physical features appear in plants found in different locations
- logically, the same response is seen for the production of secondary plant compounds
Purpose of Secondary Metabolites?
- attract pollinators and seed dispersers
- deter growth of other competing plant species
- act as signals between plants and symbiotic organisms
- defense
Attracting pollinators and Seed Dispersers
- fruits are brightly coloured to attract birds ( they disperse seeds far from parent
- when seeds are developing fruit is not as palatable and lacks color, they may contain secondary compounds, change in test and color occur when seeds are ready to be dispersed
- fruits may contain compounds that deter insects and are still edible for birds and mammals
What is flower color and smell often a product of?
- phenolic compounds like anthocyanidine or anthocyanins
- both belong to large class of molecules called Flavonoids
- synthesized through the combination of amino acids: phenylalanine and tyrosine
- anthocyanidins + sugar = anthocyanins
What role for anthocyanidins and anthocyanins play?
- both play a role in plant protection from reactive oxygen species (ROS)
- some suggested health benefits related to quenching ROS
Define Alleopathy
chemical defence to defend territory
Deter growth of other plant species
- plant defence against other competitors
- plants release toxins into soil or air that discourages other plant species from growing
- many examples of these volatile compounds are terpenes orphenolics
Examples of volatile compounds (terpenes or phenolics)
- juglans nigra (black walnut) releases juglone into soil, inhibits seed germination of specific plant competitors
- Eucalyptus regnans (eucalyptus) lead litter produces allelopathic chemicals against some soil microbes and plant species
- Ailanthus altissima (tree of heaven) roots produce Ailanthone to kill of surrounding plants
Symbiotic Signals between plants
- plant communication may be cooperative
- plants may release volatile secondary metabolites when damaged or stressed
Function of VOC’s
- when released, VOC’s may signal neighbouring plants of the same species to activate defences before being attacked themselves
- may also. be received by plants of different species
- if the different species plant can appropriately perceive the signal, it too can increase its defence mechanisms
example of Volatile Compound Communication
- sage tomato
- when crushed, sage releases methyl jasmonate
- jasmonate stimulates nearby tomato plants to produce protease inhibitory that kill grazing insects
Jasmonic acid and Methyl Jasmonate
- lipid derived plant hormones involved in regulation of plant development (derived from linolenic acid)
- produced in response to plant damage
- increased levels activate signaling pathways and expression of secondary compounds
Plant defence
- plants produce secondary compounds to reduce grazing (predators include bacteria, fungi, insects and mammals)
- secondary compounds work due to a variety of characteristics (bad taste, physiological effect, reproductive and developmental effects
Why do grazers avoid the Coca plant and coffee leaves?
due to the presence of alkaloid compounds
- glycoalkaloids bind to cell membranes of skin cells on mouth and tongue to break down tissues lining mouth and stomach
What family do the sprouting potato and unripe tomato come from?
the Solanaceae family
Coumarin
- found in sweet clover
- is a phenolic compound
- over-ingestion causes internal bleeding in mammals
What are some other examples of Coumarin and its uses?
- synthetic coumarin used as rodenticide (known as Warfarin)
- other derivatives are used medicinally, treatment for strokes and blood clots (known as Coumadin)
Polyacetylene
- a photosensitive and activated compound
- produced by daisies
- armyworms eat daisies - if worm is exposed to sunlight, the compounds it ingested become toxic and result in worm’s death
Furanocoumarins
- light induced chemical toxins for defensive purposes (St. john’s wort, Rue, Buckwheat)
- phenolic compounds like flavanoids that absorb UV light (protect plants from DNA damage)
- ingestion of these plants followed by sun exposure may result in skin rashes on the predator
Photodermatitis
- when plant oils containing furanocoumarins contact skin
- exposure to sunlight following plant ingestion or contact can cause irritation, blistering, hyperpigmentation of the skin
Psoriasis Treatment
- Psoriasis is an immune system condition that results in thick, red, scaly skin patches
- psoralen is a furanocoumarin that is used to treat psoriasis
Name Anti-Insect Strategies
- toxic compound production
- compound production (pest deterrent)
- Volatile emission
- mutagens
What are some terpene compounds widely used by humans (insecticides)
- red cedar terpenes repel moths in clothes closets
- mummies prepared with pine and fir resins to deter insects
- neem trees produce azadirachtin, a complex insecticidal terpene with extra properties
How do insects fight back to defences of the plant?
- eating strategies (ex. daisy worm has specialized mouthparts)
- adapt to plant chemical strategies
- gains ability to metabolize specific toxic secondary compounds
- borrowing chemical strategies (danaid butterflies)
- attracted to toxic plant chemical
What is a necrotroph
a parasitic organism that kills the living cells of its host and then feeds on the dead matter
What is a biotroph?
any parasite that cannot survive in a dead host and therefore keeps its alive
What is a hemibiotroph?
an organism that is parasitic in living tissue for some time and then continues to live in dead tissue
Describe the plant immune system
- Pathogen-associated molecular patterns (PAMP)- triggered Immunity (PTI): pathogen detected by plant Pattern recognition receptors
- effector-triggered susceptibility: pathogens suppress plant PTI
- effector-triggered immunity: plants have acquired ‘R’ proteins that detect effectors and create a secondary response
What are the three main components of plant defence signalling?
- salicylic acid
- jasmonic acid
- ethylene
What is the role of Salicylic acid in the intracellular signalling cascade?
- triggers a change in the cells redox potential
- this causes the translocation of NRP1 to the nucleus to activate SA-regulated genes
What is the role of Jasmonic acid in the intracellular signalling cascade?
- triggers the proteasomal degradation of JAZ
- reduction of JAZ (JA gene transcriptional repressor) results in elevated transcription of JA genes
What is the role of Ethylene in the intracellular signalling cascade?
- triggers signalling by repressing protreasomal degradation of ET responsive transcription factors
