Plant responses to abiotic stress + herbivory Flashcards
Examples of abiotic stresses:
Changes in day length,
Cold/heat,
Lack of water,
Excess water,
High winds,
Changes in salinity.
Describe process of abscission:
Phytochromes detect falling light levels.
Decreases auxin production
Increase ethene levels
Ethene activates genes in cells in abscission zone to produce digestive enzymes.
Enzymes digest cell wall in separation zone
Vascular bundles = sealed off
~~>Ensure no chemicals escape/leave
Why is abscission useful?
Reduce energy needed to maintain leaves in winter
Fallen leaves insulate roots
Rotten leaves provide minerals to plants.
How to combat lack of water?
Root hair cells detect fall in water levels
Produce ABA
ABA travels to leaves and bind to receptors on guard cells
Ions move out of guard cells via ion channels
~~>affects WP gradient
Water leaves by osmosis
Guard cells become flaccid + close stomata
What is photoperiodism?
Plants are sensitive to lack of light in their environment.
How do plants combat fall in temperature?
If cells freeze –> membrane disrupted = die.
Cytoplasm + sap in the vacuoles contain solutes which lower the freezing point.
~~~> act as antifreeze
Different genes suppressed + activated in response to fall in temperatures
What are physical defences in response to herbivory?
Thorns
Spikes
Hairy leaves
Chemical defences in response to herbivores:
Tannins –> bitter taste, toxic to insects
Alkaloids –> bitter taste, poisonous to animals (affect metabolism
Terpenoids –> toxic to insects + fungi (neurotoxins, repellants)
Pheromones –> affect social behaviours of other members of same species
VOCs (volatile organic compounds) –> same as pheromones but affect other species
What do pheromones do?
How plants communicate with each other
Signals leaves of other plants to make callose
~~~> strengthens cell wall when plant is damaged
What is the folding response in mimosa pudica?
Scares animals off
fold in response due to touch
Contains toxic alkanoids
