Adaptations of Plants to Anaerobiosis - University of Florida
Transcript of Adaptations of Plants to Anaerobiosis - University of Florida
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Biogeochemistry of WetlandsS i d A li tiS i d A li ti
Institute of Food and Agricultural Sciences (IFAS)
Science and ApplicationsScience and Applications
Wetland Biogeochemistry LaboratorySoil and Water Science Department
Adaptations of Plants to Anaerobiosis
6/22/2008 WBL 16/22/2008 16/22/2008 WBL 1
InstructorMark Clark
Soil and Water Science DepartmentUniversity of Florida
Adaptations of Plants to Soil AnaerobiosisAdaptations of Plants to Soil Anaerobiosis
Topic Outline
Role of oxygen in the plant
Potential stresses due to lack of oxygen
Physiological and morphological adaptations
Gas transport processes
6/22/2008 WBL 2
Oxidation of the rhizosphere
Flux of reduced gases
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Learning Objectives
Adaptations of Plants to Soil AnaerobiosisAdaptations of Plants to Soil Anaerobiosis
Understand impacts of hypoxia and anoxia on plants.
Understand physiological and morphological adaptations that wetland plants have to overcome or minimize stress.
Learn about passive gas exchange processes that occur in wetlands vegetation.
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Understand what an oxidized rhizosphere is and what implications it has for the plant and soil biogeochemistry.
Realize that gas transport is a bidirectional pathway.
Plants and Al
Water Air
OXYGEN: Sources and SinksOXYGEN: Sources and Sinks
Soil OxygenSoil OxygenSoil OxygenSoil Oxygen
Algae Release byPlant Roots
Oxidation ofOxidation of Reductants
Respiration
Chemolithotrophicoxidation
Chemicaloxidation
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Do wetland plants require ?
Do wetland plants require ?oxygen?oxygen?
Do all plant organs require oxygen?
Do all plant organs require oxygen?oxygen?oxygen?
Drained SoilDrained Soil
Gas Exchange in Soil / Water / Plant System
Flooded SoilFlooded Soil
OO22
OO22
COCO22CO2, CH4, andother gases
Dissloved metalssulfides, and organic acids
?
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Glucose Absence of Oxygen
Presence of Oxygen
Glucose MetabolismGlucose Metabolism
Pyruvate
Acetyl-CoAAcetate
Acetyl-CoA
Lactate
32 ATP32 ATP 2 ATP2 ATP
Electron transport chain
O2 + 2H+
H2O
Acetaldehyde
Ethanol
TCA Cycle
Stresses on plant Stresses on plant Decrease in Cell Energy Charge
Can’t produce or maintain enzymes and cell membrane Glycosidic acidosis due to loss of ion gradientsGlycosidic acidosis due to loss of ion gradientsHormonal imbalance
Accumulation of toxic compounds under anaerobic metabolism (acetaldehyde, ethanol)Cyanogenesis
Hydrolysis of cyanogenic glycosides produce CyanideDeath by Anaerobic Starvation
Inefficient metabolism of non structural carbohydrates
Water BalanceSuberization and loss of root area for water uptake
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Adaptation to soil anaerobiosisAdaptation to soil anaerobiosisAdaptation to soil anaerobiosisAdaptation to soil anaerobiosisPhysiological Adaptations
Anaerobic respirationAnaerobic respirationAlternative metabolic byproducts
Morphological AdaptationsExternal: Prop roots, Pneumatophores, Lenticels, Stem Elongation,Internal: Aerenchyma, Hypertrophied Stems
Oxidized RhizosphereOxidizing the root environment via radial oxygen lossPrecipitation of dissolved metals in the root zoneOxidation of reduced compounds in the root zone
How Does Oxygen/Air How Does Oxygen/Air ygygEnter the Plant?Enter the Plant?
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Stomates
Typically associated Typically associated with leaves, can be found on herbaceous stems.Open and closed by guard cells, regulated by CO2 and moisture.Li k b tLink between atmosphere and vascular bundles.
http://www.cropsci.uiuc.edu/ocgs/cpsc399/PlantsystemsSu02.htm
LenticelsPores that form between the atmosphere and the cambium l f t d t klayer of stems and trunksTriggered by ethylene productionOnly occur on woody speciesIncrease gas transfer to the cambiumHave greatest concentration near the air water interfaceHave been shown to influence O2 concentration in Red Mangrove prop roots by 90% if blocked.
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XylemOuter Bark
Lenticels
O2
O2
O2
O2
Lenticels
PhloemCortex
CO2CH4
O2O2
Prop RootsProp RootsModified root, only found in Red Mangrove Speciesin Red Mangrove SpeciesEach Root originates from the trunk above the water surfaceRoots are very spongy and porousLenticels on roots just above the air/water interface provide connection with atmospheric oxygenOxygen concentration measured in roots as high as 15-18%
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PneumatophoresModified root
perpendicular to main t i h i t lroots running horizontal
just below the sediment surfaceFound only in Black Mangrove speciesLenticels on root provideLenticels on root provide connection to atmospheric O2 when exposed above the water surface
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Mangrove
AirCO2
Water
Pneumatophores
Soil
Stem / PetioleStem / PetioleElongationElongation
Elongation of stem not i t d ith llassociated with cell
replication.Triggered by inundation and most likely linked to increases in ethylene concentration.Maintains connectionMaintains connection between atmospheric oxygen and below-water organs of the plant.
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What are the Internal What are the Internal Passageways for Gas Transfer?Passageways for Gas Transfer?
Hypertrophied Hypertrophied StemStem
Swelling along stem/trunk not associated with growth but resulting from the enlargement of cellsButtressing in treesExpanded tissue canExpanded tissue can provide passageway for gases between the atmosphere and below-water tissue
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AerenchymaAerenchyma
Genetically predisposedDevelop with growthSensitive to ethylene induced cellulase
InducedResponse to increased concentration of ethyleneethylene
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AerenchymaAerenchymaGenetically PredisposedGenetically Predisposed
Cattail RootT hTypha latifolia
Aerenchyma (intercellular air space)
Induced AerenchymaInduced Aerenchyma
Synthesis of 1-aminocyclopropand-1-carboxylic acid
(ACC)
Primary Root
(ACC)
10 cm
O2 Ethylene ACCACC
aerobic 2 day anaerobic 4 day anaerobic
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Porosity influenced by redox potentialPorosity influenced by redox potential
30
40
sity
(%) a
bb
10
oss
oo
t d-1
)20
10
0
Roo
t por
os
bb
5
0
-200200 -300
Eh (mV)
Rad
ial O
2lo
(ÎĽm
ol g
-1dr
y ro
a
Kludze and DeLaune, Sci. Soc. Am J., 1938)
How do Gases Move InsideHow do Gases Move InsideHow do Gases Move Inside the Plant?
How do Gases Move Inside the Plant?
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Oxygen movementOxygen movementthrough the plant through the plant
DiffusionDiffusion - due to partial pressure diffdifferencesConvective / Mass flowConvective / Mass flow - due to total pressure differences as a result of thermo-osmotic pressure differences at the leaf surface.
Temperature inducedpHumidity inducedCO2 solubilizationVenutri effect
1 meter
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Upper Leaf Surface
Leaf SectionLeaf Section
Porous Partition (<0.1 mm)
StomataN2
Surface
Lower Leaf Surface
EnergyInternal PressurizationInternal PressurizationTemperature Induced Temperature Induced
T0 P0
PorousPartition
(< 0.1 um)
T1T2P1
P2
T1 = T2 > T0
P1 > P2 > P0
PorousPartition
(> 0.1 um)
old leafnew
leaf
T0 = temperature outsideT1 = temperature inside new leafT2 = temperature inside old leaf
P0 Pressure outsideP1 Pressure inside new leafP2 Pressure inside old leaf
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Effect of temperature and age of leafEffect of temperature and age of leaf
120
100
ΔT = 1K
ΔT = 5K100
80
60
40
(mL
air h
-1)
ΔT = 8K
20
0Young Old
Leaf AgeGrosse, 1989
Internal PressurizationHumidity Induced
Internal PressurizationHumidity Induced
[ H2O ]o[O2 , CO2 , N2]0
P
Energy
PorousPartition
(< 0.1 um)
PorousPartition
(> 0.1 um)
old leafnew
leaf
[ H2O ]1[ H2O ]2[ O2 ]1
[ O2 ]2
[H2O]1 = [H20]2 > [H20]o
[O2, CO2, N2]1 > [O2, CO2, N2]o
P0
P1P2
[H2O]0 = Humidity outside[H2O]1 = Humidity inside new leaf[H2O]2 = Humidity inside old leaf
[O2]0 Concentration outside[O2]1 Concentration inside new leaf[O2]2 Concentration inside old leaf
P0 Pressure outsideP1 Pressure inside new leafP2 Pressure inside old leaf
P1 > P2 > P0
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AtmosphereAir Intake
Young Leaves
Old Leaves
Air IntakeAir Exhaust
Water
Floodwater
Air Intake
Air Exhaust
RhizomeSoil
Rhizome
Mass flow –CO2 Solublization
Mass flow –CO2 Solublization
Water
Air Air
Plant
CO2
CO2
Air
N2
CO2
O
O2
Air
O2
O2
CO2(aq)
HCO⇆CO 2
O2
O2
O2
N2
N2
Leaf Water
N2CO2
O2
CO2
O2
O2
CO2(aq)
HCO3-⇆CO3
2-
O2
(Redrawn from Taskin, I., and Kende, H., Science 1985)
O2
N2
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peed
Mass flow - Venturi Effect
Air
Win
d sp
Air
Drained SoilDrained Soil
Gas Exchange in Soil / Water / Plant System
Flooded SoilFlooded Soil
OO22
OO22
COCO22CO2, CH4, andother gases
Dissloved metalssulfides, and organic acids
?
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Oxidized RhizosphereOxidized RhizosphereMost adaptations discussed relate to longitudinal transfer of oxygen to root.Oxygen concentration inside root is high, oxygen concentration outside root low/absentStrong concentration gradient can results in radial oxygen loss (ROL) forming an Oxidized Rhizosphere.
Oxygen Levels in Root and Oxidized Rhizosphere (cross section)
Phragmities australis7mm back from apex
W. Armstrong et al 2000, Annals of Botany 86:687-703
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Oxygen Levels in Root and Oxidized Rhizosphere (cross section)
Phragmities australis100 mm back from apex
W. Armstrong et al 2000, Annals of Botany 86:687-703
Oxygen Levels in Root and Oxidized Rhizosphere (longitudinal profile)
T. D. Colmer, 2003, Plant, Cell and Environment 26, 17-36
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Conceptual model of oxidized rhizosphere with barrier to ROL near
root base
Oxygen Flux Phargmites australis
O2 Flux
2.08 g/m2 dayg y
Root Respiration2.06 g/m2 dayNet Release
0.02 g/m2 dayBrix and Schierup, 1990
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CarbonCarbon NitrogenNitrogen
Oxidation-Reduction
O2 + Aerobic soil
Anaerobic soil
O2
NO3- NH4
+O2 + Aerobic soil
Anaerobic soil
O2
OMCO2
OM NH4+OM VFA
IronIron ManganeseManganese
Oxidation-Reduction
O2 + Aerobic soil
Anaerobic soil
O2
Mn4+ Mn2+O2 + Aerobic soil
Anaerobic soil
O2
Fe2+Fe3+
Mn4+ Mn2+Fe3+ Fe2+
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Oxidizing Activity of Roots
Toxicity of reduced compounds (e.g., lfid ) i d dsulfides) is decreased.
Supports nitrification and methane oxidation.Precipitates metals and in some cases nutrient uptake is decreasednutrient uptake is decreased.
Does Gas Transport Only Occur Does Gas Transport Only Occur p yin One Direction?
p yin One Direction?
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O
Methane Exchange Through Plant
CH4
CO2
O2
WaterO2 + CH4 CO2
Atmosphere
SoilCH4
2 4 CO2
CH4 O2 CO2+
100
80 Methaneur
Gas Exchange through PlantsGas Exchange through Plants
60
40
20
Methane
Oxygen
flux,
mg/
m2
hou
Sagittaria Canna Scirpus Scirpus Typha Pontederia
0
latifolia flaccida pungens validus latifolia cordata
Emergent aquatic macrophytes
Gas
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Learning Objectives Summary
Loss of oxygen has significant implications for plant metabolism/survival.
W tl d d t d l t h h i l i l dWetland adapted plants have numerous physiological and morphological adaptations to deal with these stresses.
Movement of gases within the plant is the result of a combination of diffusive and convective mechanisms.
Radial oxygen loss from roots result in an oxidized rhizosphere that significantly increases the aerobicrhizosphere that significantly increases the aerobic-anaerobic interface in a wetland and can reduce anaerobic stress on vegetation.
Gas exchange is bidirectional: oxygen in - reduced gases out.