Module 5: Plant responses to abiotic stress Flashcards
Give 5 examples of abiotic stresses for plants
1)changes in day length
2)extreme heat or cold temps
3)lack of / excess water
4)high winds
5)changes in salinity (dissolved salt content of water)
What is meant by photoperiodism?
the sensitivity of plants to levels of light in their environment
Photoperiodism aligns the plant with the changing seasons , make 1 point about how plants adapt in each season
summer-daylight hours are at maximum and trees are in full leaf which maximises photosynthesis and growth
autumn-lengthening of dark periods triggers leaf fall
winter-daylight hours are at minimum and trees maintain a period of dormancy
spring-days lengthen and temps rise so trees come out of dormancy
Name the pigment that plants use to sense the duration of light and darkness
How many forms does this pigment exist in and what makes each form different?
phytochrome
has 2 forms which absorb different wavelengths of light
Give 3 triggers of leaf abscission in plants
-lengthening of dark periods which reduces photosynthesis rate
-energy demands for respiration outweighing glucose availability
-need for dormancy to avoid winter-related damage
Give the first 3/9 points for the process of leaf abscission
(start with a decrease in light)
1)decrease in light prompts a decrease in auxin levels
2)leaves release the hormone ethene
3)ethene switches on genes in cells within the abscission zone at the base of the leaf stalk
Give the next 3 points for the process of leaf abscission
4)enzymes digest and weaken cell walls in the separation layer
5)vascular tissues are sealed off which blocks transport to the leaf
6)fatty material is deposited into cells in the inner protective layer of the abscission zone
Give the final 3 points for the process of leaf abscission
7)cells within the separation layer swell with water which puts strain on weakened cell walls
8)environmental factors (eg wind) separate the leaf from the plant
9)the protective layer forms a scar which prevents entry of pathogens
Give 3 examples of plant responses to freezing temperatures
-synthesising sugars amino acids and proteins that act as antifreeze and prevent the cytoplasm from freezing
-modulating gene expression to bolster cold resistance
-adjusting sap solute concentrations to lower freezing point
What do plants use the hormone ABA for?
they use it as a signal for conserving water during periods of heat and drought
Give 5 points about the mechanism of ABA action
(start with low water availability)
1)low water availability triggers ABA production
2)ABA moves from roots to leaves
3)ABA binds to receptors on guard cells
4)ABA activates changes in ionic conc. of guard cells which lowers their water potential and turgor
5)this results in the stomata closing to reduce water loss
