Flooding tolerance of native and nonnative grasses: variation in photosynthesis, transpiration, respiration and carbon isotope

discrimination

Elizabeth WaringThesis Defense

Wetlands and Invasion

• Nonnative plants are those that are introduced in an area due to intentional or accidental methods (Pysek et al. 2004)

• Nonnative to invasive• Wetlands are particularly likely to be

invaded– Sinks in hydrological systems– Seeds and plant parts are easily dispersed by

water or flotation

Flooding

• Importance to wetlands• Effects of flooding on vegetation

• Drought mode

Cheyenne Bottoms Oct. 2007

http://geospectra.net/cheyenne/bottoms

• Previous flooding studies focused on biomass accumulation as indicator of tolerance to disturbance

• Examine physiological changes in species due to flooding

Why study physiology in invasive species?

Physiological processes are the link between environment and performance

GrowthReproduct

ion

Metabolic

Adaptations

Disturbances

Flooding

Performance

Physiological

Processes

Environment

Phragmites australis

• “common reed”• Few native populations

in North America• Hybrid of native and

Eurasian population

• C3 photosynthetic species

• Wetland indicator: FACW

• Model wetland invasive species www.uvm.edu

Phalairis arundinacea

• “reed canarygrass”• Few native

populations in North America

• Mostly hybrid of native European and Asian populations

• C3 photosynthetic species

• Wetland indicator: FAC

Invasive.org

Sorghum halepense

• “johnsongrass”• Native to

Mediterranean Europe and Africa

• Invasive to croplands

• C4 photosynthetic species

• Wetland indicator: FACU

• Has been seen invading flooded ditches

www.wi.dnr.gov

Spartina pectinata

• “prairie cordgrass”• Native to Kansas

• C4 photosynthetic species

• Wetland indicator: FACW

Questions• Do Phragmites, Phalaris, and Sorghum

have greater photosynthetic capabilities in flooded conditions compared to Spartina?

• Determine if nonnative species demonstrate adaptations to tolerate flooding better than native species? – increased ADH activities

Flooding setup

CollectionDepthsTreatments

• Flooding Measurements– After 7 days

• Measurements with LI-6400

– After 28 days• Measurements with LI-6400• Harvest roots for ADH assay tests• Leaves collected for carbon isotope analysis

“I once had a zoologist friend who worked on limpets. His opinion was ‘Photosynthesis is fine – just as long as plants don’t stop doing it.’ If you really do not care about how life on Earth converts sunlight to sustain the biosphere, then you have no natural curiosity. And, probably, no soul.”

-John F. AllenLund University

(Raven et al. 2005)

Pmax

Quantum Efficiency

Carbon fixation

• Repeated measures analysis of variance (RM ANOVA) were used on data collected at 1500 PPFD for photosynthesis (A)– Within species were analyzed to test for

differences between treatments

• RM ANOVA also used to analysis Pmax and net qe

Spartina pectinata, prairie cordgrass (native)

After 7 days close ratesAfter 28 days clear preference to deep floodingInteraction of time X trt significantly higher (p=0.044)

Phragmites australis, common reed (nonnative)

Always favors flooded conditionsNo significant differences

Phalaris arundinacea, reed canarygrass (nonnative)

After 7 day no preferenceAfter 28 days clear difference between deep flooding and other treatments--- 3 deep flooded plants diedSignificantly different over time (p=0.029)

Sorghum halepense, johnsongrass (nonnative)

After 7 days does well After 28 days all deep flooded and 3 medium flooded plants diedA significantly decreased over time (p<0.001)

Spartina 7 days

Sorghum 7 daysPhalaris 7 days

Phragmites 7 days

Spartina 28 days

Sorghum 28 daysPhalaris 28 days

Phragmites 28 days

P=0.001 RM ANOVA, interaction of time X spp

• p=0.027 in interaction of time X spp

• Tukey’s HSD post-hoc used

• Spartina > Phalaris & Phragmites > Sorghum

• No significant differences between times or interactions

• Low observed power

A Pmax

Spartina ↑ ↑Phragmites ↑ ↑Phalaris ↑↓ ↑↓Sorghum ↓ ↓

Oxygen evolution

Maximum JO2

Gross qe

O2

evo

luti

on

O2

• RM ANOVA p>0.05 over time and interactions

• JO2 indicates

damage to PSII

• No significance differences indicates impact in photosynthesis is not in PSII

• RM ANOVA p=0.014 over time

• p=0.001 in interaction of time X spp

• Tukey’s HSD: Phragmites >

Phalaris & Spartina > Sorghum

A Pmax

Spartina ↑ ↑Phragmites ↑ ↑Phalaris ↑↓ ↑↓Sorghum ↓ ↓

JO2 gross qe

↑ ↑↑ ↑↓ ↓↓ ↓

Fluorescence

• 3 pathways– Photochemistry, heat, light

• Fluorescence is measure of light re-emitted by plant

• Fv/Fm is the dark adjusted efficiency of excitation capture by PSII

• Maximum of 0.83• Measure of health of PSII

• RM ANOVA p<0.001 over time and interaction of time X spp. p=0.005 interact of time X trt

• Tukey’s HSD : Spp: Phragmites > Phalaris & Spartina >Sorghum

Trt: Medium > Low & Deep > Dry

A Pmax JO2 gross qe

Spartina ↑ ↑ ↑ ↑Phragmites ↑ ↑ ↑ ↑Phalaris ↑↓ ↑↓ ↓ ↓Sorghum ↓ ↓ ↓ ↓

Fv/Fm

↑↑↓↓

• Ratio of 13C/12C in leaf can give information on photosynthesis

• Reported on a “per mil” basis (parts per thousand, ‰)

• Differs based on photosynthetic typeFrom Stable Isotope Ecology, Fry 2008

C3 plants

• Phragmites and Phalaris

• 1st step in C3 photosynthesis involves conversion of CO2 to 3-carbon acid

• Enzyme involved (Rubisco) has higher affinity to 12C

• If stomata are closed, expect increase in ‘heavy’ carbon

C4 plants

• Spartina and Sorghum

• 1st step in C4 photosynthesis involves conversion of HCO3 to 4-carbon acid

• Enzyme involved (PEPCase) has higher affinity to 13C

• If stomata are closed, expect increase in ‘light’ carbon

• Two-way ANOVA used• p<0.001 between trt• Tukey’s HSD: Deep> Med & Low > Dry

A Pmax JO2 gross qe Fv/Fm

Spartina ↑ ↑ ↑ ↑ ↑Phragmites ↑ ↑ ↑ ↑ ↑Phalaris ↑↓ ↑↓ ↓ ↓ ↓Sorghum ↓ ↓ ↓ ↓ ↓

13C

↓↓↑−

ADH assays

• Alcohol dehydrogenase (ADH) catalyzes ethanol production in fermentation.

• The more ADH produced the better the plant respires anaerobically.– Can be an indicator of

adaptation to environment.

Pyruvatedecarboxylase

Pyruvate

CO2

AcetaldehydeNADH

NAD+

Ethanol

ALCOHOL DEHYDROGENASE

Different types of adaptations shownp<0.001 between species and p=0.032 in the interaction of species and treatment

A Pmax JO2 gross qe Fv/Fm 13C

Spartina ↑ ↑ ↑ ↑ ↑ ↓Phragmites ↑ ↑ ↑ ↑ ↑ ↓Phalaris ↑↓ ↑↓ ↓ ↓ ↓ ↑Sorghum ↓ ↓ ↓ ↓ ↓ −

ADH

↑−↑↑↓

www.uvm.edu

www.wi.dnr.gov

Future research

• Bigger sample sizes• Low observed power

• Conduct field studies

• If field and greenhouse results overlap than can be applied to management plans

Acknowledgments• Dept. of Biological Sciences• Li-Cor LEEF grant• Kansas Academy of Science• Thesis Committee• Dr. Channell for statistical assistance• Dr. Ray Lee for isotope assistance• Ms. Susan Eaton for greenhouse assistance• Elita Baldridge, Jessica Casey, Ashley

Inslee, and Georgina Jacquez

Isotopes

From Stable Isotope Ecology, Brian Fry, 2008