16.2 Plant responses to abiotic stress

Question 1

what are examples of abiotic stresses which plants experience

Answer 1

lack of water/excess water
lack of light
suboptimal temperature
suboptimal soil pH

Question 2

what is photoperiodism and what changes in a plant is it responsible for

Answer 2

photoperiodism = a plants sensitivity to lack of light in environment
its responsible for
leaf bud dormancy
timing of flowering
tuber formation

Question 3

how does abscission help a plant survive

Answer 3

during winter, light intensity decreases
cost of glucose (to maintain leaves & produce antifreeze) > glucose produced by photosynthesis
∴ loses leaves to conserve glucose.
leaves regrow when photosynthesis becomes efficient

Question 4

how do plants prevent freezing

Answer 4

after long periods of no light
plants actively transport salts
—> vacuole + cytoplasm
lowers melting points, preventing freezing

Question 5

why can most plants not survive sudden frost having anti-freeze measures

Answer 5

during sudden frost, plants cannot prepare by actively transporting salts into vacuole to lower melting point
∴ water freezes & expands,
increasing turgor pressure & causing cell to burst

Question 6

describe the mechanism by which stomata close

Answer 6

1.Roots detect abiotic stress - lack of water
2.ABA (abscisic acid) released ⟶ vascular system
3. Binds to receptor on guard cell
4. Triggers active transport of ions out of guard cell ⟶ surrounding solution
5. Water moves out of guard cell by osmosis, down water potential gradient
6. Guard cells become flaccid & close

Question 7

why must plants be able to respond to their surroundings

Answer 7

to survive in changing conditions
avoid abiotic stress
maximise photosynthesis
aviod herbivory