Plant responses to abiotic stress Flashcards
what does abiotic mean, give some examples
non-living factors
eg- day length, temperature, amount of water, wind speeds, salinity (amount f salt dissolved in water)
Why do deciduous trees in temperate climates experience leaf loss?
in temperate climates there is very varied conditions- temperature, amount of daylight
light and temp affect rate of photosynthesis
when the amount of glucose required for respiration to maintain leaves and to produce chemicals from chlorophyll that may protect them against freezing, is greater than the amount of glucose produced by photosynthesis.
Strong winds- blow leaves off or blow tree over
What is photoperiodism?
plants are sensitive to lack of light in their environment
What different plant responses are affected by the photoperiod?
dominancy of buds- they open up
the timing of flowering in a plant
when tubers are formed in preparation for overwintering
how does day length affect a plant- in how its specifically absorbed?
light sensitive pigment- phytochrome- Pr or Pfr, each absorbs diff type of light and their ratio changes depending on the levels of light
What does the lengthening of dark periods trigger?
abscission
period of dormancy during the winter months
Describe the process of abscission, due to less light
falling light levels= falling conc of auxin = leaves produce hormone ethene
at base of leaf stalk is abscission zone= 2 layers of cells sensitive to ethene- separation zone and protective layer
ethene initiates gene switching in these cells= new enzymes that digest outer layer of abscission zone = separation layer
the protective layer forms before the leaf falls- vascular bundles are sealed off and fatty material is deposited forming this layer, preventing entry of pathogens
cells in separation zone respond to hormonal cues, retain water and swell, putting more strain on weakened outer layer
other conditions like wind or cold temperatures can speed up the process of the leaf then falling
How do freezing temperatures affect a plant?
cells freeze, membranes are disrupted and they will die
How do some plants prevent damage from freezing?
cytoplasm and sap in vacuole contain solutes which lower the freezing point
some produce sugars, polysaccharides, amino acids, proteins = act as antifreeze, prevent cytoplasm from freezing or protect cells from damage even if they do freeze
most plants only produce chemicals making them frost resistant in winter months- produced in response to fall in temp or less time of light
what response does stomatal control have?
open stomata= water lost through transpiration by evaporation- cools leaves
stomata close to conserve water
Which hormone controls the opening and closing of the stomata in response to abiotic stress?
how does it work?
ABA
Leaf cells release ABA under abiotic stress, causing stomatal closure
recent research- roots provide early warning of water stress through ABA- when water volume in soil is low and transpiration is under threat, roots produce ABA, binds to receptors on plasms membrane of stomatal guard cells, reducing water potential, and therefore turgor of cells = stomata close
