John L. Snider
Third Year Review
Crop Physiologist
University of Georgia
Department of Crop and Soil Sciences
Responsibilities
Teaching: 15% Appointment
• Advanced Crop Production: CRSS 8050
• Crop Physiology: CRSS 4450/6650
• Graduate Student Advising
Research: 85% Appointment
•
•
•
•
•
Drought Stress
Irrigation Management
Heat Stress
Drought and Heat Tolerance Screening
Seedling Vigor
Teaching
Crop Physiology
Advanced Crop Production
Peanut
Corn
Tobacco
Cotton
Graduate Student Advisement
Graduate Student Major Advisor
• Calvin Meeks. 2014 to Present. PhD
• Daryl Chastain. 2012 to Present. PhD
Graduate Student Advisory Committee Member
• Seth Byrd. 2013 to Present. PhD
• Harold Owiti. 2014 to Present. MS
• Calvin Meeks. 2012 to 2013. MS
RESEARCH FOCUS 1
Drought Stress Physiology
&
Irrigation Management
2012 Drought Stress Study
2012 Drought Stress Study
Location
• Stripling Irrigation Research Park:
Camilla, GA
Three Cultivars
• DP 0912 B2RF, DP 1050 B2RF, PHY
499 WRF
Two Irrigation Treatments
• Dryland
• 100% Checkbook
Statistical Design/Analysis
• Split-plot, RCBD, n=4, 3
• Mixed Effects ANOVA
100 % checkbook irrigation amounts
Growth Stage
cm/week
Pre-Bloom
2.54
1st Bloom (week 1)
2.54
Week 2
3.81
Week 3
5.08
Week 4
5.08
Week 5
3.81
Week 6
3.81
Week 7
2.54
Week 8
2.54
Water Status: ΨPD ΨMD
PSII: Fv/Fm ΦPSII ETR
Temperature: Tair Tleaf
Gas Exchange: PN PG RD gs E
Summary
Measurement
How do underlying
mechanisms interact to inhibit
net photosynthesis and drive
yield loss?
Trend
Photosynthesis
↓
RD/PG
↑
gs , E
↓
Canopy Temperature
↑
PSII
=
Cultivar
=
Lint Yield
↓
Arrows indicate direction of effect for dryland
relative to 100% checkbook.
J. Plant Physiol., 2014
J. Agron. Crop Sci., 2014
Plant-Based Irrigation Scheduling
35
PN ( mol m-2 s -1 )
30
25
20
15
10
5
r 2 = 0.942
0
-1.0
-0.9
-0.8
-0.7
PD (MPa)
-0.6
-0.5
-0.4
Predawn Water Potential for Scheduling
Irrigation
Location
 Stripling Irrigation Research
Park: Camilla, GA
Design
 RCBD
 n=4
Two Cultivars
 FM 1944
 PHY 499
Five Irrigation Treatments





100% Checkbook
-0.5 Mpa
-0.7 Mpa
-0.9MPa
Dryland
Sampling
 Leaf sampled from 4th main-stem
node below the apical meristem three
days per week.
Rainfall and Irrigation: 2013 & 2014
Treatment
Irrigation
2013
Irrigation
2014
Rainfall
2013
Rainfall
2014
Total
2013
Total
2014
Checkbook
17.4
29.9
66.9
34.9
84.3
64.8
-0.5 MPa
11.5
23.7
66.9
34.9
78.4
58.6
-0.7 MPa
2.5
14.2
66.9
34.9
69.4
49.1
-0.9 MPa
0
10.0
66.9
34.9
66.9
44.9
Dryland
0
0
66.9
34.9
66.9
34.9
All data are in cm.
Predawn Water Potential (ΨPD)
-0.1
(A)
(B)
-0.3
-0.7
-0.9
-1.1
100% Checkbook
-0.5 MPa
-0.7 MPa
-0.9 MPa
Dryland
-1.3
-1.5
06/24
07/08
07/22
Date (Month/Day)
08/05
08/19
07/07
07/21
08/04
08/18
Date (Month/Day)

06/10

PD (MPa)
-0.5
2013
2014
09/01
09/15
Season-Average Predawn Water Potential
-0.1
2013
PD (MPa)
-0.3
a
a
a
a
a
c
c
b
b
a
-0.5
-0.7
-0.9
-0.1
2014 
PD (MPa)
-0.3
-0.5
-0.7
-0.9
ok
0%
10
o
kb
ec
Ch
5M
-0.
Pa
7M
-0.
Pa
9M
- 0.
Pa
Irrigation Treatment
d
n
yla
Dr
Yield x Average ΨPD
2200
Lint Yield (kg ha -1 )
2000
1800
1600
r 2 = 0.973
1400
1200
1000
800
600
-0.4
-0.5
-0.6
YPD (MPa)
Yield & WUE optimized
-0.7
TC - TaWell-Watered Baseline
Can Use This Model to Calculate Crop Water Stress Index
TC-Derived Crop Water Stress Index
1.0
2013
2014
(B)
(A)
0.8
CWSI
0.6
0.4
0.2
0.0
-0.2
10
0%
Ch
ec
o
kb
ok
M
.5
-0
Pa
M
.7
-0
Pa
M
.9
-0
Pa
D
la
ry
nd
10
Irrigation Treatment
0%
Ch
e
b
ck
oo
k
5M
-0 .
Pa
7M
-0 .
Pa
9M
-0 .
Pa
Irrigation Treatment
y
Dr
la n
d
TC-Derived Crop Water Stress Index
1.0
0.8
CWSI
0.6
0.4
0.2
0.0
2
r = 0.975
-0.2
-0.4
-0.5
-0.6
PD (MPa)
-0.7
Yield x CWSI
2200
Lint Yield (kg ha -1)
2000
1800
r 2 = 0.854
1600
1400
1200
1000
800
600
-0.2
0.0
0.2
0.4
CWSI
0.6
0.8
1.0
RESEARCH FOCUS 2
Heat Stress Physiology
&
Drought/Heat Tolerance Screening
Assessing Heat Tolerance
Assessing Heat Tolerance
T15 as a Common Heat Tolerance Threshold
0.85
0.80
Fv/Fm
0.75
0.70
o
T15 = 42.7 C
0.65
0.60
0.55
0.50
0.45
25
30
35
40
45
Incubation Temperature ( C)
50
55
Overview of Heat Tolerance Work
• Seasonal and Genotypic Differences (J. Plant Physiol., 2013)
• Stage of Plant Development (J. Agron. Crop Sci., in press)
• Thermotolerance and yield stability
• Leaf Development
RESEARCH FOCUS 3
Seedling Vigor
Multi-Location Seedling Vigor Trial
J. Cotton Sci. 2014
Current work focusing on fatty acid saturation & seedling response to temperature.
QUESTIONS?