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Plant Biology > Water Relations > Flashcards

Water Relations Flashcards

1
Q

Primary root

A

First organ to originatebfrom seed embryo

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2
Q

Secondary roots

A

Lateral roots

=> further anchoring
=> & uptake of water and nutrients

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3
Q

3 steps of water uptake

A

Uptake
Transport
Transpiration

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4
Q

Water

A

Polar solvent
=> mean of transport for solute
Medium and partner for biochemical reactions

Property of
Cohesion => attraction btw molecules => transpiration column
Adhesion => attraction to surface

Enables
Turgor: Stature & Growth
Temp regulation
Yield

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5
Q

Diffusion

A

Movement from subst. from high to low conc.

=> 2nd law of thermodynamics => stabilize env.

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6
Q

Diffusion (equations)

A

1st Fick’s law
Diffusion rate is proportional to concentration gradient

2nd Fick’s law
Diffusion time is proportional to square diffusion distance

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7
Q

Efficiency of Diffusion

A

Only in short distance

=> in large distances: additional force => Bulk flow

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8
Q

Bulk flow

A

Concerted movement of molecules en masse most often in response to a pressure gradient

Poiseuille’s equation

Volume flow rate depends on radius of vessel

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9
Q

Osmosis

A

Diffusion of water through semipermeable membrane

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10
Q

Osmotic potential

A

-RTc (c= osmolarity mol/L)

Pure water => psi (osmotic potential) is 0
Dilution of sth in water = reduction of psi

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11
Q

Water potential

A

Psi w = psi s + psi p + (psi g)
s = osmotic pressure
p = hydrostatic pressure (+ = turgor, - = tension (as in xylem))

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12
Q

Water flows

A

Passively (through osmosis) to area of lower psi

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13
Q

Deplasmolyse

A

Turgor
Pressure potential > 0

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14
Q

Plasmolyse

A

Pressure pot = 0

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15
Q

soil composition

A

Small particles enable vertical movement => better retention of water

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16
Q

Wilting point and field capacity

A

Point at which plants wilt and don’t recover and level above which soil can not take up more water

Determined by soil composition

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17
Q

Zones of root

A

Meristematic, elongation and maturation

18
Q

Symplastic pathway

A

Through plasmodesmata

19
Q

Suberin

A

Kork
Water impermeable
In casparian strip

20
Q

Aquaporins

A

6 transmembrane domains
Form tetramers
Encided by multigenic family
Highly regulated
Do not only transport water => e.g. ROS

21
Q

Xylem

A

Tracheids or vessel elements

22
Q

Pressure gradient per meter

A

Psi p/delta x

23
Q

Cohesion tension theory

A

Tranpiration of water leads to lower water potential => transpirationssog durch cohäsion

24
Q

Water loss

A

Mostly through transpiration => transport
Only very few percent directly used for photosynthesis & metabolic reactions/ growth

25
Q

Reaction to dessication

A

Mesophytes:
osmolytes
LEA
dehydrins
ROS-detoxification

Xerophytes:
cytoplasmic vitrification
leaf shrinkage or folding
protection of photopigments
vacuolar shrinkage
increase in antioxidant systems

26
Q

Xerophyte adaptions

A

Phenological: only grow/reproduce after rain, otherwise remain quiescent
Morphological: deep roots, high xylem transport/tissue storage, tiny or absent leaves
Biochemical: CAM metabolism
Anatomical: thick cuticle, rolled leaves, stomatal crypts

27
Q

Anatomical traits of Xerophytes

A

succulent (water storing leaves or stems)
thick cuticle
sunken stomata

28
Q

Water deficit Perception

A

cell turgor
membrane potential
ROS
osmotic content
others…

=> in plasma membrane (receptor kinases, channels and proteins like integrins)

29
Q

Water deficit signaling

A

Between cells:
ABA
ethylene
Hydraulic signals
Water potential
Xylem pH
Other signals…

Within cells:
ABA
ROS
transcriptional cascades
other signals…

30
Q

Water deficit Responses

A

Short term:
Decrease in stomatal conductance (close)
Alterations in hydraulic conductivity
osmotic adjustments

Long term:
induction of drought-induced genes
changes in growth rate and root architecture

31
Q

ABA impacts

A

Ion channel activity
Transcription factor activation

32
Q

Two possible responses to drought

A

ABA pathway
Or direct activation of transcription factors

33
Q

Cellular responses to desiccation

A

Shrinkage
Shriveled membrane
Fragmented vacuole
Reactive oxygen species can accumulate
Proteins can aggregate and denature

34
Q

Osmolites

A

Proteins and sugars that are able to maintain an aqueous environment around other active proteins

35
Q

LEA

A

late embryo abundant proteins
intrinsically disordered
Not properly folded
Bind to other proteins to protect them

36
Q

ROS accumulation

A

Result of stopping photosynthesis
Reduction of chlorophyll releases electron => produces ROS => very reactive => damage proteins and membrane

37
Q

ROS detoxification

A

Number of diff enzymes produced (Superoxiddismutase, Catalase, Ascobate peroxidase)
These systems are upregulated under water stress conditions

38
Q

Aquaporin regulation

A

Expression
Localization (compartments or membrane)
Activity/gating
=> by phosphorylation or binding of calcium

39
Q

ABA perception

A

PYR1/RCAR receptor
Upon binding of ABA it inhibits phosphatases
If receptor is inactive => phosphatase dephosphorylates SnRK kinases (can phosphorylate TFs and Ion channels)

40
Q

Root growth direction

A

Xerobranching (avoid desiccated areas)
Hydropatterning (grow lateral roots toward water)
Xerotropism (elongation along verical gradient)
Hydrotropism (elongation along horizontal gradient (neigung))

Primary root elongation
Preferential lateral root proliferation in deep soil
Production of short lived, drought induced lateral roots
Increase root hairs & their length & aquaporins

Plant Biology (10 decks)

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