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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
effect of increasing ionic solutes
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
effect of compatible solutes
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
what does ABA do?
stomatal closure. transported to roots + accumulates there. water stress: ABa transported from root to leaves via xylem
28
how does ABa signal stomatal closure?
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
developmental + morphological responses to water deficit
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
saline soils
- high concentration - soluble salts - NaCl among others. 6% of earth's surface
31
saline soils arise by?
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
plant processes altered by soil salinity
1. non-specific osmotic stress | 2. accumulation of Na+ and Cl- in plant tissue
33
effects of non-specific osmotic stress in plant?
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
effects of Na+ and Cl- in plant tissue
interferes w nutrient uptake. inhibit K+ uptake - cytotoxic Na+ accumulation. = protein denaturation, membrane destabilitze. - slower response but may inhibit photosynthesis + biosynthetic processes
35
define halophytes + glycophytes
H: salt-tolerant G: not adapted to salinity
36
Plant responses to saline conditions? | - glycophyte?
similar to water deficit. - accumulate compatible solutes, glyc: exclusion mechanisms to avoid salt stress.
37
Na+ exclusion mediated H+ Na+ antiporters.
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
how halophytes avoid salt stress in leaves
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
plant response to chilling vs freezing
chilling low temp >0. damage to warm climate plants. temperate plants chilling toelrant freezing <0. damage to most plants. some tolerate
40
chilling stress on membrane
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
chilling-sensitive have more saturated fatty acids
carbon-carbon double bonds = unsaturated. without double bonds = saturated. unsaturated maintain membrane fluidity at lower temps.
42
plant acclimation to chilling
sub-lethal chilling temp, plant acclimate membrane composition to increase fludity => lipid desaturase to increase FA desaturation - creates db in FA.
43
molecular chaperone proteins protect sensitive proteins + membranes during abiotic stress
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
plant affected by freezing
intracell: lethal. water can expand + burst through extracell: happens before intracell. bc lower solute content. freeze at lower temp bc lower water potential
45
freezing + cell dehydration
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
capacity of species to avoid spontaneous intracellular ice formation determines their low-temp limit
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
plant acclimation to freezing
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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