plant growth regulators: what agronomists need to...
TRANSCRIPT
Plant Growth Regulators: What Agronomists Need to Know
Sheri Strydhorst, PhD Research Scientist – Agronomy Alberta Agriculture and Rural Development
Agronomy Update January 20, 2015
Why should you care?
Why is
western Canadian ag
excited?
Cost to agriculture… Lodging can reduce yields from 7-35%
Greatest yield reductions occur when lodging happens within 20 days after anthesis
Assumes an 85 bushel/acre crop; Wheat price of $3.29/bushel (Sept 29, 2014 YEG); Farm size of 1500 acres, 40% of acres in wheat (600 acres).
Lodging during ripening can increase grain sprouting, decreasing grade
Yield Loss Bushels Lost Lost income Farm loss 7% 6 bu/acre $19.74/acre $11,844
15% 13 bu/acre $42.77/acre $25,662 35% 30 bu/acre $98.70/acre $59,220
Fischer and Stapper (1987). Lodging effects on high-yielding crops of irrigated semidwarf wheat. Field Crops Res 17:245-258.
The primary goal of PGRs is to…
A. Increase Yields B. Reduce Lodging and Improve Harvestability C. Increase Tillering D. Aid in Residue Management E. B and D
Plant Growth Regulator Use in the
UK Crop % receiving PGR Apps/year
winter wheat 89 1.7
winter barley 77 1.4
winter oats 78 1.4
75% of PGR applications contain chlormequat
2006 -Department for the Environment Food and Rural Affairs, London
Slide Source: Phil Bernardin, Technical Representative, ENGAGE Agro
What are PGRs? • Plant Growth Regulators • Synthetic compounds that
impact hormonal activity to beneficially modify plant growth and development
• Effective at low concentrations &
break-down rapidly • Many economically important
PGRs work by reducing cell elongation and lowering the rate of cell division http://chartdiagram.com/tag/plant-cell-diagram/
How do they work? They alter natural plant hormonal activity:
Gibberellins – Stimulate longitudinal growth Auxins – 1o stimulate cell elongation & shoot
growth Ethylene – Synthesized in response to stress and
ripening Cytokinins – Stimulate cell division Abscisic Acid – Regulates germination, protein
stores in developing seeds and stomatal closure during water stress
Brassinosteroids – Broad spectrum of simulative and protective activities
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2 Main PGR Groups: Ethylene releasing compounds
i.e. Ethephon (also blocks auxin transport)
Inhibitors of GA biosynthesis i.e. Chlormequat-Chloride & Trinexapac-Ethyl
ethylene
Rademacher, 2000. Growth retardants: Effects on gibberellin biosynthesis and other metabolic pathways. Annu. Rev. Plant Physiol. Plant Mol. Biol. 51:501-31.
PGRs alter GA but may also… • Increase cytokinins • Lower ethylene levels • Increase ABA Possibly causing… • Delayed senesence • Increased resistance to
environmental stress • Shifting assimilates to the
roots leading to increased cytokinin formation
These effects are NOT achieved by all PGRs in all plant species
Comparison of Standard PGR Products used in the UK
Standard chlormequat
Trinexapac ethyl
Mode of action Inhibits early stages of gibberellin biosynthesis
Inhibits late stages of gibberellin biosynthesis
Minimum temperature 80C 100C
Onset of action slow fast Residual activity long short
Source: Wilhelm Rademacher - Control of Lodging in Intense European Cereal Production
Slide Source: Phil Bernardin, Technical Representative, ENGAGE Agro
PGRs on the Prairies In western Canada:
Chlormequat chloride (ENGAGE AGRO) was registered for wheat this summer
Trinexapac-ethyl is in the process of registration for wheat
Ethephon (Ethrel), by Bayer CropScience, is not actively promoted for use in Western Canadian Cereal production
http://www.usask.ca/agriculture/plantsci/winter_cereals/
Staging is critical
When to apply GA inhibitors? GS 30-32 (June 16)
BBCH 30 Beginning of stem elongation: pseudostem and tillers erect, first internode begins to elongate, top of inflorescence at least 1cm above tillering node.
BBCH 31 First node at least 1cm above tillering node
Lancashire, P.D., Bleiholder, H., Van Den Boom, T., Langeluddeke, P., Strauss, R. Weber, E., and Witzenberger, A. 1991. A uniform decimal code for growth stages of crops and weeds. Ann. Appl. Biol. 119:561-601.
When to apply Ethephon? GS 37-45
Field View • Canopy closure
Individual Plant • 30 - 40 cm tall
Tillers Separated
Main Stem View
Main Stem
1st tiller
2nd tiller
3rd tiller 1st 2nd
3rd
5th 4th
6th
7th 8th - Flag
BBCH 37 – Flag leaf just visible, still rolled BBCH 39 – Flag leaf fully unrolled, ligule just visible BBCH 45 – Late boot, flag leaf sheath swollen BBCH 49 – First awns visible
How do PGRs change plant physiology? Reduced stem length Uppermost internodes and
peduncle are shortened (Berry et al 2000)
Inconsistent reports of PGRs altering stem diameter
Even if tillers are not exposed to the PGR, the elongation retarding effect can be observed on the tiller (Peltonen-Sainio et al 2003).
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Internode length tends to be reduced with PGR use. Rather than a reduction in the number of internodes.
Undesirable PGR results… Shoot elongation!! (Clark and Fedak, 1977) Why?
Increased GA precursors result from CCC application.
CCC breaks down and GA synthesis resumes, excess precursors result in elevated GA levels
Not observed with trinexapac-ethyl Only short term height reduction (Rajala and
Peltonen-Sainio, 2002) Unproductive tillers
Increased tillering? Increased
photoassimiliate availability
PGR induced changes in hormonal patterns
http://www.mississippi-crops.com/2011/02/04/spring-nitrogen-fertility-suggestions-for-wheat/
Environmental conditions to avoid with PGRs
Is yield impacted?
http://www.flaman.com/agriculture//image.php?width=475&image=http://www.flaman.com/agriculture/images/products/Twister%20Flat%20Bottom-small.jpg
What has the research found?
PGR use in Wheat Main Shoot Growth
# of Tillers Root Weight
Yield vs. control in outdoor pot trials
Ethephon Reduced Increased No effect
No effect
Chlormequat Chloride
Reduced No effect
Decreased No effect
Trinexapac-Ethyl Reduced Increased No effect
No effect
Pot experiment conducted in Helsinki, Findland. Greenhouse and outdoor trials Rajala and Peltonen-Sainio, 2001. Plant growth regulator effects on spring cereal root and shoot growth. Agron. J. 93:936-943.
26/01/2015
92 a 90 a 98 b
60 A 59 A 65 B
109 a 109 a 115 b
0
20
40
60
80
100
120
140
Control CCC PGR B Control CCC PGR B Control CCC PGR B
Lethbridge High River Killam
Whe
at Y
ield
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Wheat Stacked 2014 - Yield Response to PGR at High to Adequate Moisture Environments
26/01/2015
92 b 86 a
91 b
71 B 65 A
71 B
0
10
20
30
40
50
60
70
80
90
100
Control CCC PGR B Control CCC PGR B
Bon Accord Falher
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Wheat Stacked 2014 - Yield Response to PGR at Dry Environments
26/01/2015
1.4% Yield Increase
Do all species and cultivars respond the same?
Ontario study with CCC found…
• Wheat was the most responsive
• Barley intermediate response
• Oats were the least responsive
Clark and Fedak, 1977. Effects of chlormequat on plant height, disease development and chemical constituents of cultivars of barley, oats and wheat. CJPS 57:31-36.
29.8%
11.6%
8.8%
Comparison of 53 ON barley varieties…
Most 2 row barley cultivars were in this group
10 of the 15 barley varieties with an esterase- isozyme were in this group
15 varieties were taller
5 varieties had no response
33 varieties showed some height reduction
Clark and Fedak, 1977. Effects of chlormequat on plant height, disease development and chemical constituents of cultivars of barley, oats and wheat. CJPS 57:31-36.
What has the research found?
PGR use in soft red winter wheat
# of Tillers Lodging Yield vs. control
Ethephon No effect Reduced lodging
Similar or slight
decrease
Chlormequat Chloride
No effect Similar to control or reduced
Increased in 1 of 4
cv’s
Field experiments conducted at Lafayette, Indiana Lodging was not a serious problem in either year of the study and
was more impacted by cultivar than PGR
Knapp and Harms, 1988. Nitrogen fertilization and plant growth regulator effects on yield and quality of four wheat cultivars. J. Prod. Agric. 1:94-98.
Economics
Manipulator - Cost? Crop Rate Cost Farm Cost* Wheat 0.70 L/acre $13.84/acre $8,304 Barley 0.93 L/acre $18.39/acre $2,759
Manipulator - Returns? Crop Price (Sept 29/14 –
YEG) Additional Yield Required to Breakeven
Feed Wheat $3.29/bushel 4.2 bushels/ac Barley $2.74/bushel 6.7 bushels/ac
Faster harvest speeds, more harvestable yield, RISK MANAGEMENT TOOL
*Farm size of 1500 acres, 40% of acres in wheat (600 acres); 10% of acres in barley (150 acres).
What do we still need to learn?
Unanswered questions… Why do some varieties respond and others do
not? Would we see more benefit with tank mixing
chlormequat chloride and trinexepac ethyl? Do we have the correct growth stage? Are dual applications useful? How do environmental conditions impact
performance? Does seeding rate matter?
Summary
PROs PGRs produce
shorter (2-15cm), thicker, and stronger stems which reduce lodging
The primary use of
these PGRs is as a harvest management aid
Risk management
tool
CONs Application timing is critical
Stage carefully and accurately to avoid: increased tillering reduction in grain yields
Weather conditions may have a negative impact on performance
Cultivars respond differently or not at all
