Triggering of events Flashcards
Why do plants respond?
To increase evolutionary fitness as this maximises number of successful offspring
Why are plant responses needed?
The environment is uneven and variable both biotically and abiotically
How are plant responses coordinated?
By hormones which are released by cells
How are plant hormones released?
By the whole organism so are decentralised
How do plant hormones move?
By diffusion, active transport as mass flow so need to be small
What are the types of triggering events?
Timed events through life and protecting against biotic and abiotic factors
What are examples of time events through life?
Fruit ripening, seed germination, responding to abiotic stress and leaf loss
What are examples of protecting against biotic and abiotic stress?
Responding to abiotic stress and producing defences against herbivory
What controls fruit ripening?
Ethene
What is a climacteric fruit?
It needs ethylene for ripening and continues to ripen after being picked
What are examples of climacteric fruits?
Apples, bananas, mango, peach, pears, avocado and melon
What is non-climacteric fruit?
Fruit that does not need ethylene to ripen
What are examples of non-climacteric fruit?
Citrus, grapes, watermelon and strawberries
How do supermarkets deal with ripening fruit?
They pick before ripe and keep cold so they can spend longe before becoming ripe and fruit is firm to reduce damage during transport
What controls seed germination?
Gibberellins
What inhibits germination?
Light, other than in certain plants such as poppies
What is experimental evidence for the role of giberellins?
If mutant plants which lack to gene to produce gibberellins are produced, they will not germinate, but if gibberellins are applied, they will germinate.
How do plants deal with abiotic stress when born into darkness?
Grow pale, as no chlorophyll and long and thin to maximise resources before reaching light
How do plants cope with reeling?
Leaf loss, cytoplasm and vacuole contain solutes with lower freezing point and production of sugar, polysaccharides, amino acids or proteins to act as anti freeze
Why do leaves fall off?
Reduce the chance of storm damage, nutrients can be re absorbed, little photosynthesis, minimise water loss and can use resources to prevent freezing
What is senescence and abcission?
Growing brown and falling off
What inhibits senescence?
Cytokines
What inhibits abscission?
Auxins
What happens when there is a drop in cytokines?
Senescence is initiated
What is the result of senescence initiation?
A reduction in auxin production
What is the result of a reduction of auxin?
Cells in the abscission zone become sensitive to ethene and this initiates cellulose production with digest cell walls, causing abscission
What is synergism?
The interaction of 2 factors where the outcome is greater than the sum of the individual effects of either of them
What is antagonism?
The interaction of 2 factors that are driving the outcome in opposite directions
What are the environmental triggers for freezing response?
Sustained fall in temperature and reduction is day length
What controls stomatal closure?
Absicic acid?
When do stomata close?
When water is in short supply or in the dark
When do leaf cells release ABA?
When under stress
When do roots release ABA?
When soil water levels are low
What happens when ABA is released?
Guard cells swell, stomata opens so ions move out of guard cells and water follows by osmosis, then guard cells become flaccid and stomata closes
What are physical defences?
Hairs, thorns and spikes
Wha is a movement defence?
Leaf folding of mimosa pudica
What are volatile organic compounds?
Parasitoid attractants and inducers of defence
What are examples of chemical defences?
Citronellal (an insect repellant), caffeine (toxic to fungi and insects) and tannin (bitter taste and toxic to insects)
