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bot 340 midterm > abiotic stress > Flashcards

abiotic stress Flashcards

1
Q

define stress

A

negative influence on plant performance by external abiotic or biotic factors.

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2
Q

understanding stress response important why?

A

understanding crop roductivity + ecological stability

- explain geographical distn of species.

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3
Q

biotic stress

A

caused by living organism

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4
Q

abiotic stress

A

caused by physical of chemical factor

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5
Q

plant responses to abiotic stress involve what trade-offs?

A

btw vegetative + repro growth

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6
Q

annual plants vs perrenial

A

annual: switch quickly to reproductive growth under stress.
perennial: direct more energy to storage to enable survival to next season

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7
Q

define acclimation

A

increased tolerance of individual plant following exposure to prior stress event
- periodic exposure to stress, or increasing stress intensity

physiological/morphological changes associated require no genetic mods + are reversible

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8
Q

define adaptation

A

population’s tolerance to particular stress increases by natural selection over many generations.
permanent, heritable changes to genome

susceptible : fail to reproduce under stress
tolerant: survive to produce, increase frequency tolerant alleles in popln

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9
Q

adaptation + stress avoidance

A

adaptation leads to stress avoidance.
- can change life cycle to avoid stress = ephemeral plants complete life cycle during optimal periods

  • reduce impact of stress even tho stress is present
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10
Q

water deficit stress

A

inadequate water: water content of cells/tissues is less than highest water content observed under hydrated conditions

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11
Q

drought stress

A

lack of water due to inadequate rainfall

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12
Q

dessication stress

A

excess transpirational loss from leaves

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13
Q

spectrum of ddrought-coping plants

A

dessication susceptible: injury to moderate water deficit

dessication resistant: adaptive features that enable escape, avoid, tolerate drought stress

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14
Q

drought escape:

A

avoid stress by copleting life cycle when adequate moisture is available.

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15
Q

two mechanisms to adjust vegetative + repro growth according to water availabiltiy

A

rapid phenological development: rapid plant growth, produce minimal number of seeds before soil water depletes

developmental plasticity: plant show little growth during dry season, grow indeterminately in wet season = large amount of seed

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16
Q

dessication avoidance

A

maintain higher tissue water content under low water availability

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17
Q

2 dessication avoidance strategies

A

minimization of water loss: water conserved. reduce transpiration, radiation absorption

optimize water uptake: increase rooting, hydraulic conductance

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18
Q

dessication tolerance

A

ability to continue functioning while enduring low tissue water content

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19
Q

adaptive traits of dessication tolerance

A

maintenance of cell turgor through osmotic adjustment + CW elasticity
- increase metabolic resistance to low tissue water content

20
Q

changes in cell with water deficit

A

cell dehydration - decrease turgor pressure
(need + turgor pressure for plant growth, cell expansion)
inhibition of cell expansion

21
Q

water deficit + growth -areas grow different?

A

shoot stops growing. reduced leaf expansion bc less transpiration loss.
root growth continues = still trying to find water

22
Q

results of water deficits?

A

ion cytotoxicity = cell dehydration increases ion concentration in cytosol = ion toxicity

induces abscisic acid (ABA) accumulation. = stomatal closure, inhibit photosynthesis

23
Q

what is osmotic adjustment?

A

capacity of plant cells to accumulate solutes in order to make solute potential more negative during periods of water deficit
- lower water potential in roots to absorb water still.
to -0.2–08 or less

24
Q

two modes of osmotic adjustment

A
  1. increase ionic solutes

2. compatible solutes

25
Q

effect of increasing ionic solutes

A

uptake from soil, transport ions from other plant organs to root.
inhibit cell metabolism, unless restricted to vacuoles.
- electrically balance with accumulation of anions.
= lower water solute potential

26
Q

effect of compatible solutes

A

organic compounds accumulate in cytosol

  • llower water solute potential.
  • no adverse effects on metabolism. -
  • ex: proline, sorbitol, glycine betaine
  • synthesis of compatible solutes has energy and carbon cost
27
Q

what does ABA do?

A

stomatal closure.
transported to roots + accumulates there.
water stress: ABa transported from root to leaves via xylem

28
Q

how does ABa signal stomatal closure?

A

accumulates in guard cells
- trigger Ca2+ influx
= Ca-activated anion effluc opens, lose anions from guard cells.
= inhibit PM H+-ATPase - depol PM, open VgK+effluc, K+ lost
= lost solutes, increase water solute potential. water exits, turgor decrease, stomata closes

29
Q

developmental + morphological responses to water deficit

A
  1. reduce leaf area: reduce cell expansion, alter leaf shape, senescence + abscission
  2. leaf orientation: orient away from sun to minimize overheating
  3. develop trichomes, thickened cuticle restrict water loss + increase light reflection
  4. root-to-shoot biomass ratio increases during water deficit. - leaf reduces, root still forws. more energy + photosynthates to support root growth. ABA regulates root:shoot ratio during water stress
30
Q

saline soils

A
  • high concentration
  • soluble salts
  • NaCl among others.
    6% of earth’s surface
31
Q

saline soils arise by?

A

saltwater intrusion into coastal soil
soil salinizaiton: more water leaving surface by evaporation than entering by infiltration. = over-irrigation, wash salt downward when it rans, salt not draining

32
Q

plant processes altered by soil salinity

A
  1. non-specific osmotic stress

2. accumulation of Na+ and Cl- in plant tissue

33
Q

effects of non-specific osmotic stress in plant?

A

more negative soil solute potential = more negative soil water potential.
- more negative soil water potential reduces water potential gradient between root + soil, leading to water deficit stress in plant

= reduce leaf expansion + shoot growth

34
Q

effects of Na+ and Cl- in plant tissue

A

interferes w nutrient uptake. inhibit K+ uptake

  • cytotoxic Na+ accumulation. = protein denaturation, membrane destabilitze.
  • slower response but may inhibit photosynthesis + biosynthetic processes
35
Q

define halophytes + glycophytes

A

H: salt-tolerant
G: not adapted to salinity

36
Q

Plant responses to saline conditions?

- glycophyte?

A

similar to water deficit.

  • accumulate compatible solutes,
    glyc: exclusion mechanisms to avoid salt stress.
37
Q

Na+ exclusion mediated H+ Na+ antiporters.

A

driven by pmf across PM and tonoplast.

-glycophytes pump most of accumulated Na+ back to enviro to reduce toxic salt load in tissue.
== high energy expenditure tho

38
Q

how halophytes avoid salt stress in leaves

A
  1. deposit high amounts of Nacl in vacuoles
  2. deposit high amounts of NaCl in specialized external structures (epidermal bladder cells) = sequester salt away from metabolism.
39
Q

plant response to chilling vs freezing

A

chilling low temp >0. damage to warm climate plants. temperate plants chilling toelrant

freezing <0. damage to most plants. some tolerate

40
Q

chilling stress on membrane

A

affect fluidity.
- damage cell membrane. unevenly gelled, some areas still liquid = solid gel. increases membrane permeability

temp btw fluid and gel varies btw species.
transition at higher temp when more saturated fatty acids

41
Q

chilling-sensitive have more saturated fatty acids

A

carbon-carbon double bonds = unsaturated.
without double bonds = saturated.

unsaturated maintain membrane fluidity at lower temps.

42
Q

plant acclimation to chilling

A

sub-lethal chilling temp, plant acclimate membrane composition to increase fludity
=> lipid desaturase to increase FA desaturation - creates db in FA.

43
Q

molecular chaperone proteins protect sensitive proteins + membranes during abiotic stress

A

molecular chaperones interact w protein to facilitate protein folding, reduce misfoling + stabilise tertiary structure.

=heat shock proteins, made in response to environmental stressors.

  • molecular shielding: dehydrins are highly hydrophilic, bind protein, membrane protect from abiotic stress like dehydration + chilling
44
Q

plant affected by freezing

A

intracell: lethal. water can expand + burst through
extracell: happens before intracell. bc lower solute content. freeze at lower temp bc lower water potential

45
Q

freezing + cell dehydration

A

extracell ice formation decrease water potential of remaining apoplastic fluid.

  • unfrozen water exits symplasm down water gradient toward ive.
  • cell dehydrates. PM damaged as pulls away from CW. - similar response to water deficit
46
Q

capacity of species to avoid spontaneous intracellular ice formation determines their low-temp limit

A

can accumulate compatible solutes - reduce water solute potential.
more negative water potential decrease water potential gradient btw inside + outside of cell + reduce water loss from cell.
- contributes to supercooling. cell water remains liquid bc solute content

47
Q

plant acclimation to freezing

A

lower sub-zero temp, intracell ice formation occurs
= damage/rupture.
- melting cause protein denaturation
- synthesis of antifreeze proteins to counteract ice formation.
- AFP bind to small ice crystal to inhibit ice crystal growth

bot 340 midterm (6 decks)

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