1. Comparing Drought Response in Two Riparian Species Platanus
occidentalis L. (American Sycamore) and Salix nigra Marshall
(Black Willow) for Use in Riparian Restoration
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Joshua Hashemi, Eric Duncan, Chelsea A. Harris, Reuben Hilliard
and Paula C. Jackson
6. • To compare the performance of American Sycamore
Platanus occidentalis L.) to Black Willow (Salix nigra
Marshall) under field and greenhouse conditions.
• Determine if Arbuscular Mycorrhizae play a role in species
response to water treatments.
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Goals
7. AM in maize root.
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Do Arbuscular Mycorrhizae (AM) play a role in drought
tolerance?
8. Overall Objectives
Field:
• Compare species in terms of:
• CO2 assimilation
• Water use
• AM colonization
• Perform spore extraction from soil to ensure that homogenized field soil
may be used as AM inoculum in greenhouse experiment.
Greenhouse:
• Across differing treatments of water and AM* availability, compare:
• CO2 assimilation
• Anatomical growth
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* A fungicide (Benomyl) was used to preclude AM fungal growth. All treatments had field soil as a source of
AM spore inoculum.
10. CO2 assimilation and Water Use in the field
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Amax was determined from light curves
generated using a LICOR 6400
photosynthesis system n=6 Platanus,
n=4 Salix
Water Use was determined using Thermal
Dissipation Probes (TDP)
n= 3 Platanus
n= 5 Salix
11. CO2 Assimilation Field
-3
0
3
6
9
12
15
0 200 400 600 800 1000 1200 1400 1600
ACO2(µmols/m2/s)
PPFD (µmols/m2/s)
CO2 assimilation (Field)
P. occidentalis
S. nigra
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Mean photosynthetic light curves for both species. Values represent species means (Platanus n=6, Salix
n=4). Measurements were taken in August 2013 on fully expanded leaves with healthy color and
appearance. Eric Duncan MSIB Thesis
• No significant difference in field CO2 assimilation rates.
• Differences in CO2 assimilation rates in greenhouse
experiment were expected to result from treatments
12. R² = 0.5905
R² = 0.4629
0
0.2
0.4
0.6
0.8
1
0 500 1000 1500 2000 2500 3000
Sapflow(g/cm2/min)
VPD Pascals
Sap flow and VPD
Salix
R² = 0.5189
R² = 0.4641
0
0.2
0.4
0.6
0.8
1
0 200 400 600 800 1000
Sapflow(g/cm2/min)
PAR (µmol/m2/s)
Sap flow and Light
Salix
Platanus
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Water use was higher in Salix and both had a strong relationship to PPFD (r =
0.68 Platanus; r = 0.72 Salix; p< 0.01) and to VPD (r = 0.68 Platanus; r = 0.77
Salix; p< 0.01)
Platanus
13. Mycorrhizal colonization level in field
• 10 individuals were sampled per species (20 trees total)
• Root samples were taken from a riparian area with a small (<
1 m wide) perennial stream at Kennesaw State University in
North West Georgia.
• Distance and orientation relative to the water source were
registered.
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Field sample site – Kennesaw State University
14. Mycorrhizal colonization level in field
• Roots were stained with 0.05% trypan solution.
• AM Quantification was performed using the root piece
method and the root piece estimation method.
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Colonized root stained with 0.05% Trypan BlueStaining of field samples in 0.05% trypan blue
15. Mycorrhizal colonization level in field
Root Piece Method:
• 160, 1cm root segments
• Root samples were checked for the presence or absence of
colonization
Root Piece Estimation Method:
• 160, 1cm root segments
• Root samples were given a
ranking based on level of
colonization
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Root Piece Estimation
Rank % Colonization
0 0%
1 1-25%
2 26-50%
3 51-75%
4 76-100%
16. Field Sample Colonization Results
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Salix nigra Colonization
Platanus occidentalis Colonization
Observed
With AM Without AM TOTAL
Platanus 28 132 160
Salix 56 104 160
TOTAL 84 236 320
Expected
With AM Without AM TOTAL
Platanus 42 118 160
Salix 42 118 160
TOTAL 84 236
CHI-SQUARED TEST
0.000374489P < 0.001
Root Piece Method:
Root Estimation Method:
Comparison of rank abundance.
Abundance was significantly higher in
Salix.
Mann Whitney U Test
P = 0.023
17. Soil sampling and spore extraction
• Soil samples were taken from two perennial streams
on Kennesaw State University’s campus (NW
Georgia).
• Soil was filtered through sieves and centrifuged in
sucrose solution to isolate spores.
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18. Field Spore Extractions
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Site 1 – Kennesaw State University, and spore sample
Site 2 – Kennesaw State University, and spore sample
19. Objectives
Greenhouse:
• Compare CO2 assimilation and anatomical
growth among species across different
treatments of AM* and water availability.
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* A fungicide (Benomyl) was used to preclude AM fungal growth. All treatments had field
soil as a source of AM spore inoculum.
21. Greenhouse Experimental Design
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A randomized complete block design was used to account for
possible microclimate differences within the greenhouse.
Treatments:
B4 A1
C3 D2
B8 A5
C7 D6
Table 2 Table 1
Letter Treatment
A Fungicide*/Wet+
B No Fungicide/Drought-
C No Fungicide/Wet
D Fungicide/Drought
* Addition of Benomyl, + Watered M/W/F, - Watered M/F
22. Greenhouse methods
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Anatomical measurements:
• Plant height
• Measured with a meter stick as
• (end height – initial height) cm
• Stem width
• Measured with a caliper as:
• (end width-initial width)cm
• n=31 Platanus; n=34 Salix
• n=15-17 per treatment
Gas Exchange measurements were
taken using a Licor 6400 IRGA.
27. Greenhouse Results – Platanus anatomical
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All visualizations created in Tableau 9.0
28. Conclusions - Greenhouse
• Based on Physiological Responses
• Both species had similar light curves
• Further analyses may be required to distinguish treatment differences
• Based on Anatomical Results
• Drought seemed to have a greater effect on Salix than on Platanus
• Platanus had a higher rate of growth
• Based on Fungicide Addition*
• As seen earlier, field data showed higher colonization rates in Salix,
however Fungicide did not have as strong an effect on Salix in
Greenhouse results
• Fungicide improved performance for Platanus growth under both Wet and
Drought conditions.
• Possibly decreased the incidence of detrimental fungi
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*Need to look at AM colonization in roots
29. Overall Conclusions
• Salix appeared to have higher water use, with
a stronger dependence on abiotic factors (VPD
and PPFD)
• Salix had stronger response to drought
• Both points may indicate a lack stomatal control?
• Our findings show that Platanus is a strong
contender for potential use in restoration
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30. Acknowledgements
• Dr. Paula Jackson
• Dr. Tony Golubski
• Dr. Sigurdur Greipsson
• KSU Office of the Vice President of Research Grant
• KSU Center for Excellence in Teaching & Learning
Undergraduate Research and Creative Activity Grant
• KSU Graduate Student Association Grant
• Kennesaw State University Department of Ecology,
Evolution, and Organismal Biology
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33. Granier’s Equation
K= 0.0206 u0.8124
K= (ΔTmax – ΔT)/ ΔT
U= 119 x 10-6K1.231
http://www.dynamax.com
u= Mean Sap Flux Velocity
Flow= u x area
Sap flow
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