Plant physiology summary
L1 water & transport
Plants need water for:
- Firmness & growth
o More water -> more photosynthesis -> more primary production = CO2 fixation
- As a solvent
o Polarity: polar molecules dissolve
o H-bridges: adhesion & cohesion
- Transport
o Xylem = takes water + nutrients up
o Phloem = takes carbohydrates from production to use/storage, bidirectional
Need a lot: lose a lot via stomata during CO2 uptake
Change in homeostasis -> stress
Water potential = Ψw = potential energy of water, ability to perform work
Ψw = Ψs + Ψp + Ψg in Pa = J/m3 = N/m2
Osmotic + hydrostatic + gravitational
Osmotic potential = Ψs = - ∏ (osmotic pressure)
- Ψs = -(n/V) * R * T with n = particles , V = volume, R = 8.314, T = temp
- In plants < 0; in pure water = 0
- From hypotonic to hypertonic movement
- More dissolved particles -> higher, but negative -> lower
- Temp has only small effect
Hydrostatic pressure = Ψp
- From turgor = cell wall pressure: Ψp > 0
- From tension from cohesion of water in rising vessel: Ψp < 0
Gravitational potential = Ψg
- Ψg = pw * g * h with p = density, g = 9.81, h = height
- From position of water, mostly determined by height
- Always > 0, higher location, higher Ψg
- Only matters above +-10 m
Lower water potential -> water moves towards
Main driver is difference in Ψp between roots (uptake) and leaves (use)
Most water lost via evaporation: atmosphere has lower pressure -> diffusion
Elastic modulus = ε = elasticity of cell wall, depends on turgor pressure
- ε = ΔΨp/(ΔV/V)
- Higher -> more turgor
Transport inside cell: via diffusion, only short distances
Influenced by temp, distance and solvents
Water in/out cell: via aquaporins (= channels) + bit via bilipid layer, very slowly
Diffusion from leaf to atmosphere: via stomata
,Stomata opened or not determined by:
- CO2 concentration
- Ψw
Stomatal conductance = gs; leaf conductance = gl -> both decrease when stomata’s close
Guard cells in turgor -> open; guard cells not in turgor -> close
Other factors that influence evaporation:
- Humidity of atmosphere
- Temperature
- Wind
- Humidity of soil
- Light
Xylem
Vessels: angiosperms + some gymnosperms and ferns
Tracheids: gymnosperms, ferns and angiosperms
Both consist of dead cells (appoptosis), with reinforced cell walls (ligine)
More tracheids than vessels -> weaker wood. Vessels are thiner and stronger
Cavitation = water column in xylem breaks, air bubble = emboly
Water has to be pushed up from bottom = active process
- Active transport of ions to root xylem
- Ψs increases btwn cortex and vessel
- Transport of water to xylem
- Ψp increases
- Mass flow of water, decreasing the embolies
Guttation = droplets at end of leaves through hydathodes; water is pushed out
Water transport through cortex:
- Symplastic = via cytoplasm of cells
- Apoplastic = via cell walls
Transport into vessel always symplastic: Casparian strip in endodermis is impermeable to water
Clay contains more water available for uptake than sand:
more particles -> more water bound -> higher potential of soil
diural rhythm of water potential:
more water uptake during day, cause bigger
difference in potential
biggest difference in potential btwn:
leaf – outside and leaf cell – intercellular space
L2 nutrients
, Nutrient = building block that is taken up from soil,
determines bio-productivity together with water uptake
Yield-nutrient slope isn’t linear: doesn’t make much
difference after needed amount
Need for fertilizer is increasing in developing countries
But stocks of important nutrients are finite
Macronutrient = need a lot of it
N, K, Ca, Mg, P, S, Si
Micronutrient = only need a little bit -> still important, but toxic when too much
Cl, Fe, B, Mn, Na, Zn, Cu, Ni, Mo
Deficiency zone = too little
Adequate zone = enough
Toxic zone = too much
Nitrogen (N)
Large quantities
Used for: proteins, photosynthesis
o NH4 -> glutamate -> aa’s -> proteins
Available: NO3, NH4, or aa
o N2 fixation by bacteria/electrical sources: root nodules/rhizobium
o If taken up as NO3: NO3 -> NO2 -> NH3/NH4, but NO2 and NH3 toxic
o If taken up NH4: acidification of soil -> adaption
Uptake: with transporter proteins, NRT and AMT or ammonium passively
deficiency: chlorosis = no chlorophyll -> yellow leaves
o Only in bottom leaves, can reuse nitrogen
o + more lateral roots -> N in topsoil
Phosphorus (P)
Relatively high quantities (less than N)
Used for: nucleotides, ATP, phospholipids, sugars…
Available: inorganic molecules like HPO4, H2PO4
o Organic compounds need to be broken down before uptake
Uptake: transporter proteins, PHT
o Mycorrhiza help most plants get P
Deficiency: no ATP -> no transport -> accumulation of sugars and anthocyanin
o More lateral roots + roothair -> P in topsoil
o Smaller leaves, thin stems, old leaves die
Sulfur (S)
L1 water & transport
Plants need water for:
- Firmness & growth
o More water -> more photosynthesis -> more primary production = CO2 fixation
- As a solvent
o Polarity: polar molecules dissolve
o H-bridges: adhesion & cohesion
- Transport
o Xylem = takes water + nutrients up
o Phloem = takes carbohydrates from production to use/storage, bidirectional
Need a lot: lose a lot via stomata during CO2 uptake
Change in homeostasis -> stress
Water potential = Ψw = potential energy of water, ability to perform work
Ψw = Ψs + Ψp + Ψg in Pa = J/m3 = N/m2
Osmotic + hydrostatic + gravitational
Osmotic potential = Ψs = - ∏ (osmotic pressure)
- Ψs = -(n/V) * R * T with n = particles , V = volume, R = 8.314, T = temp
- In plants < 0; in pure water = 0
- From hypotonic to hypertonic movement
- More dissolved particles -> higher, but negative -> lower
- Temp has only small effect
Hydrostatic pressure = Ψp
- From turgor = cell wall pressure: Ψp > 0
- From tension from cohesion of water in rising vessel: Ψp < 0
Gravitational potential = Ψg
- Ψg = pw * g * h with p = density, g = 9.81, h = height
- From position of water, mostly determined by height
- Always > 0, higher location, higher Ψg
- Only matters above +-10 m
Lower water potential -> water moves towards
Main driver is difference in Ψp between roots (uptake) and leaves (use)
Most water lost via evaporation: atmosphere has lower pressure -> diffusion
Elastic modulus = ε = elasticity of cell wall, depends on turgor pressure
- ε = ΔΨp/(ΔV/V)
- Higher -> more turgor
Transport inside cell: via diffusion, only short distances
Influenced by temp, distance and solvents
Water in/out cell: via aquaporins (= channels) + bit via bilipid layer, very slowly
Diffusion from leaf to atmosphere: via stomata
,Stomata opened or not determined by:
- CO2 concentration
- Ψw
Stomatal conductance = gs; leaf conductance = gl -> both decrease when stomata’s close
Guard cells in turgor -> open; guard cells not in turgor -> close
Other factors that influence evaporation:
- Humidity of atmosphere
- Temperature
- Wind
- Humidity of soil
- Light
Xylem
Vessels: angiosperms + some gymnosperms and ferns
Tracheids: gymnosperms, ferns and angiosperms
Both consist of dead cells (appoptosis), with reinforced cell walls (ligine)
More tracheids than vessels -> weaker wood. Vessels are thiner and stronger
Cavitation = water column in xylem breaks, air bubble = emboly
Water has to be pushed up from bottom = active process
- Active transport of ions to root xylem
- Ψs increases btwn cortex and vessel
- Transport of water to xylem
- Ψp increases
- Mass flow of water, decreasing the embolies
Guttation = droplets at end of leaves through hydathodes; water is pushed out
Water transport through cortex:
- Symplastic = via cytoplasm of cells
- Apoplastic = via cell walls
Transport into vessel always symplastic: Casparian strip in endodermis is impermeable to water
Clay contains more water available for uptake than sand:
more particles -> more water bound -> higher potential of soil
diural rhythm of water potential:
more water uptake during day, cause bigger
difference in potential
biggest difference in potential btwn:
leaf – outside and leaf cell – intercellular space
L2 nutrients
, Nutrient = building block that is taken up from soil,
determines bio-productivity together with water uptake
Yield-nutrient slope isn’t linear: doesn’t make much
difference after needed amount
Need for fertilizer is increasing in developing countries
But stocks of important nutrients are finite
Macronutrient = need a lot of it
N, K, Ca, Mg, P, S, Si
Micronutrient = only need a little bit -> still important, but toxic when too much
Cl, Fe, B, Mn, Na, Zn, Cu, Ni, Mo
Deficiency zone = too little
Adequate zone = enough
Toxic zone = too much
Nitrogen (N)
Large quantities
Used for: proteins, photosynthesis
o NH4 -> glutamate -> aa’s -> proteins
Available: NO3, NH4, or aa
o N2 fixation by bacteria/electrical sources: root nodules/rhizobium
o If taken up as NO3: NO3 -> NO2 -> NH3/NH4, but NO2 and NH3 toxic
o If taken up NH4: acidification of soil -> adaption
Uptake: with transporter proteins, NRT and AMT or ammonium passively
deficiency: chlorosis = no chlorophyll -> yellow leaves
o Only in bottom leaves, can reuse nitrogen
o + more lateral roots -> N in topsoil
Phosphorus (P)
Relatively high quantities (less than N)
Used for: nucleotides, ATP, phospholipids, sugars…
Available: inorganic molecules like HPO4, H2PO4
o Organic compounds need to be broken down before uptake
Uptake: transporter proteins, PHT
o Mycorrhiza help most plants get P
Deficiency: no ATP -> no transport -> accumulation of sugars and anthocyanin
o More lateral roots + roothair -> P in topsoil
o Smaller leaves, thin stems, old leaves die
Sulfur (S)
