1/26/2015 1 Understanding Plant Health & Products Bill Kreuser http://turf.unl.edu/ Characteristics of a Healthy Turf • Superintendents Perspective? • My View… 1. Efficient Energy Capture/Conversion/Utilization 2. Perceive and Adapt to Abiotic or Biotic Stress Normal “Healthy” Plant Metabolism H 2 O + CO 2 Sugar + Water Other Nutrients (N,P,K) CO 2 +H 2 O Sugar + O 2 Plant Growth Sugar Storage Seed Production Secondary Metabolites Light Energy Controlled Flow of Energy Normal/Healthy Energy Release
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1/26/2015
1
Understanding Plant Health & Products
Bill Kreuser
http://turf.unl.edu/
Characteristics of a Healthy Turf
• Superintendents Perspective?
• My View…
1. Efficient Energy Capture/Conversion/Utilization
– Burns more stored sugars and produces toxic products
Inefficiencies Increase Oxidative Stress
Absorbed electrons have to go somewhere
Free electrons forms damaging reactive oxygen species (ROS)
Different sources of stress generate damaging reactive oxygen species
Drought
Salinity
Pathogen
Stomata Close
Heavy Metals in
Soil
Production of ROS
Sub‐optimal Temps
UV & High Light
Too Much Light Energy
Plants Evolved Mechanisms to Control Reactive Oxygen Species
Production of ROS always occurs
Antioxidants
Vitamins
Pigments
Proteins
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Antioxidant Proteins Quench ROS
• Superoxide Dismutase
• Ascorbate Peroxidase
• Catalase
Plants Respond to ROS Concentrations
• ROS serve as signal molecules
– Plants adjust antioxidant concentrations
– Altered gene expression
– Hormone Levels change
– Change in physiology and morphology
• Helps the plant adapt to stress
– Abiotic and Biotic
Many stress response genes are relatedPlant Stress Preconditioning
1. Maximize growing environment to resist stress
2. Minor, non‐lethal, stress induces expression of genes to avoid or tolerate future stress
3. Exposure to one stress conditions plants to cope with a different stressful condition
Promote Healthy Growing Environment
• Fertilization
• Mowing
• Soil Management
• Proper Irrigation
• Anaerobic rootzone
• Denitrification & Leaching
• Shallow rooting
• Thatch accumulation
• Algae
• Moss
• Black layer
• Poor stress tolerance
• Poor quality playing surface (rutting, divoting)
• Poor shear strength
• Disease (pythium blight, brown patch, etc…)
• Waste of water ($$$$$)
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Deficit Irrigation Preconditions Plants to Stress
• Theory:
Water Stress → Oxida ve Stress → Plant Preps
• Common Adaptations
– Deeper Rooting
– Increased Antioxidant Production
– Reduced Respiration/Increased Carb. Storage
• Result:
– Increased Stress Tolerance
Irrigation Frequency AffectsTurfgrass Roots
0
10
20
30
40
50
60
70
80
June July August September
TNC in turfgrass roots
(mg g
‐1)
Light & frequent
Deep & infrequent
Fu, J., and P. H. Dernoeden. 2008. Carbohydrate metabolism in creeping bentgrass as influenced by two summer irrigation practices. J. Am. Soc. Hortic. Sci. 133(5):p. 678-683.
Water Stress Increases Temperature Tolerance
• Drought Preconditioned Turf Increased Heat Tolerance– Wehner and Watschke,
1981; Jiang and Huang, 2000
Jiang, Y., and B. Huang. 2001
Trinexapac‐ethyl and Stress Tolerance• Increased Water Use Efficiency
– Slightly Lower ET (King et al., 1997: Marcum and Jiang, 1998; Ervin and Koski, 2001)
– Increase Salinity Tolerance and Improved Dry Down
• (Jiang and Fry, 1998; Pessarakli et al., 2006)
• Improved Heat Stress Tolerance
– More Stress Hormones and Antioxidants (Ervin and Zhang, 2003)
– Increase Sod Storage Life in Heat (Heckman et al., 2001 & 2002)
• Increased Non‐structural Carbohydrates
– During Suppression Phase Only (Han et al., 1998 & 2004; Richie 2001; and Ervin and Zhang, 2007)
Trinexapac‐ethyl Increases Cytokinins
Species TE App 2 WAIT 4 WAIT 6 WAIT 8 WAIT
‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ ng g‐1 fwt ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐
Bentgrass + 35.1a 50.2a 42.8a 47.0a
‐ 34.7a 43.5b 36.4b 32.6b
Kentucky bluegrass + 43.0a 44.2a 32.3a 58.3a
‐ 48.0a 32.0b 29.9a 54.1b
Bermudagrass + 86.4a 85.3a 81.6a 88.9a
‐ 89.9a 72.1b 70.5b 74.0b
Ervin and Zhang, 2008
PGR Metabolism
• Decreased Efficacy During Summer– Lickfelt el al. (2005)
– Beasley and Branham (2007)
– Kreuser and Soldat (2011)
• TE Metabolism Directly Related to Air Temperature (Beasley and Branham, 2005)
– 6.4 Day Half Life at 64°F (18°C)
– 3.1 Day Half Life at 86°F (30°C)
Doubling Temperature (°C) Doubles TE Breakdown
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GDD Can Predict These TE Growing Degree Days System• Air Temperature Predicts TE Re‐application Intervals
Largest Temperature Increase Immediately After App
Pigment Field Conclusions
• Pigments Mask Turfgrass Decline
• Alleviates UV and High Light Stress
• Temperatures Increased with all Treatments
–Green Color
–Potential to Reduced Transpiration (Implications???)
The Role of Fungicides and Plant Health
Primary Role of Fungicides is Biotic Stress Avoidance
Secondary Benefits of Strobilurins• Growth Chamber Wheat:
– Increased Roots
– Increased Antioxidants
– Increased Cytokinins(Grossman and Retzlaff, 1999)
• Growth Chamber Creeping Bentgrass:
– No Differences in Visual Quality
– Occasionally Increased Root Architecture with Pyraclostrobin
Brosnan et al. (2010)
Field Evaluations of Strobilurins
University of Tennessee Research
Quality: Strobilurin > Other Fungicides Only During Disease Breakthrough
Rooting: No Difference Between Products
Strobilurins are Very Effective Fungicides
Plants Can Sense Pathogens
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Adapted from Cortes‐Barco, 2010
Civitas Primes Plant Defense (JA) Pathway
DefenseProteins
Building Blocks
AlmostJA
ActiveJA
How Does Civitas Work?
Two Potential Mechanism
1. Directly Elicits a Response (PAMP)
2. Preconditions Plants
• Civitas is Slightly Inhibiting Gas Exchange
• Mild Photoinhibition
• Oxidative Stress
• Triggers Plant Defense
Harmonizer™ Pigment Important Component of Civitas
• Limits Absorbed Light and Oxidative Stress
Civitas Reduces CO2 ExchangeRate Amax
0 A
1.3 A
2.5 B
5.1 B
10.2 C
Respiration & QuantumYield Not Affected By Civitas
Light x TMT: p<0.001
Reduced Transpiration Rate
TMT: p<0.001
15.25
15.50
15.75
16.00
16.25
0 1.3 2.5 5.1 10.2
Tran
spir
atio
n (
mo
l H
2O m
-2s-1
)
Civitas Application Rate (ml m-2)
0
1.3
2.5
5.1
10.2
A
A
C
AB
BC
Another Sign of Decreased Gas Exchange
Civitas Alters Cuticle Structure
Control 48 Hrs.
48 Hrs. 2nd App
Sign of Oil Persistence
Strive to Promote Good Agronomics First
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How to Increase Plant Health
• Reduce Environmental Stress ‐Avoidance
–Abiotic Stress
–Biotic Stress
• Increase Plant Stress Tolerance
–Precondition Plants For Stress
–Alter Plant Physiology
The Big Three!
CULTIVATION AND MOWING
Sharpness is a Good Thing!
Sharp Dull
Effect of reel/bedknife contact and sharpness on mm of shredded leaf tips
*
**
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Frequency of Clip
FOC Formula
Ground speed(inches per minute)Reel RPM
number of Reel Blades.
Preliminary Data 2005
* *
Bedknife position at various aggressiveness settings relative to center line of reel
Effect of bedknife position on basal rot anthracnose
% p
lot i
nfec
ted
NonAg
Neutral
VeryAg
NonAg
Neutral
VeryAg
NonAg
Neutral
VeryAg
0.105 0.115 0.135
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Mowing Summary
• Mower Setup Crucial to Plant Health– Mower Sharpness
– Frequency of Clip
– Aggressiveness of Cut
– Design of Mower
• Aggressive Mowing Practices Promote Disease and Annual Weeds
Irrigation Basics
• Irrigation is a primary cultural practice– Required to maintain high quality turf
• Replace rootzone water lost through evaporation and transpiration– Affected by temperature, solar radiation,
humidity, wind speed, and rooting depth
Irrigation Basics
• Amount and frequency change throughout the growing season
Under-Irrigation
Wilt
Insufficient Rootzone Moisture(under-watering)
• Slow growth (recuperative potential)
• Wilt
• Hard surface
• Susceptible to insect pests
Brown patch
Thatch accumulation
Excessive Irrigation
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Excessive Irrigation
Algae / moss
Poa annua
Excessive Irrigation
Frequent irrigation maintains soil water content at levels most prone to compaction!
• Leaching
• Anerobic rootzone
• Shallow rooting
• Denitrification
• Thatch accumulation
• Algae
• Moss
• Black layer
• Poor stress tolerance
• Poor quality playing surface (rutting, divoting)
• Poor shear strength
• Disease (pythium blight, brown patch, etc…)
• Waste of water ($$$$$)
Deficit Irrigation Preconditions Plants to Stress
• Theory:
Water Stress → Oxidative Stress → Plant Preps
• Common Adaptations– Deeper Rooting
– Increased Antioxidant Production
– Reduced Respiration/Increased Carb. Storage
• Result:
– Increased Stress Tolerance (Healthier?)
Irrigation Frequency AffectsTurfgrass Roots
0
10
20
30
40
50
60
70
80
June July August September
TNC in
turfgrass roots
(mg g‐
1)
Light & frequent
Deep & infrequent
Fu, J., and P. H. Dernoeden. 2008. Carbohydrate metabolism in creeping bentgrass as influenced by two summer irrigation practices. J. Am. Soc. Hortic. Sci. 133(5):p. 678-683.