(andropogon gerardii vitman) with seed conditioning equipment
TRANSCRIPT
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Suleyman Kavak1 and Alan G. Taylor2
1Suleyman Demirel University, Faculty of Agriculture, Isparta, Turkey
2 New York State Agricultural Experiment Station, Cornell University, Geneva , USA
Caryopsis Extraction from
Big Bluestem Spikelets by
Seed Conditioning
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Big Bluestem (Andropogon gerardii Vitman)
• Perennial, warm season grass • Used as a forage for livestock, soil conservation and as a feedstock for biofuel
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Comparison of Spikelets and Caryopses
Spikelets require 5x greater volume than caryopses for the same number of viable seeds Bulk Density • Spikelets – 125 g / l • Caryopses – 290 g / l
10,000 units in each cylinder
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Non-free flowing seeds and the Angle of repose
• If the angle of repose is > 37˚, then seeds are non-free flowing • Big Bluestem spikelets – angle of repose was 48˚
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Seed Lot Characterization ‘Niagara’
AOSA Percent Germination Spikelets 81 Caryopses 90
A spikelet may not contain a caryopsis • 59% Filled Seeds
48% Pure Live Seed (PLS)
Therefore, 2.1 kg bulk of seeds is equal to 1 kg PLS
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Water Activity • Ratio of water vapor of seed / water vapor of pure water at
a reference temperature • Water activity (Aw) x 100 = equilibrium relative humidity
(ERH)
Aqua Lab
Model 4 TE
Decagon Devices, Inc.
Pullman, WA
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Relationship of Water Added to Water Activity
y = -0.00002353x2 + 0.0078x + 0.2538 R² = 0.999
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
Wat
er a
ctiv
ity (a
w)
Water (µl/g spikelets)
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Moisture Isotherm – Big Bluestem ‘Niagara’
y = 16.568x2 – 2.0025x + 6.9946 R² = 0.997
6.0
8.0
10.0
12.0
14.0
16.0
18.0
20.0
0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00
% m
oist
ure
cont
ent o
f spi
kele
t (fr
bas
is)
Water activity (aw)
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Increasing Spikelet aw to a Desired Level • aw to seed mc method – start with moisture isotherm, then
convert aw to spikelet mc
• y = 16.568x2 – 2.0025x + 6.9946 where, y is the % spikelet moisture content x is the water activity
• a= b * (c-d) / (100-c) where, a is weight of water to add b is the initial spikelet weight c is the desired spikelet moisture content d is the initial spikelet moisture content
For each brushing treatment,
- 20 g spikelets were weighed into a jar and calculated water added
- The jar was sealed and then rotated at 30 rpm for 24 hours
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Seed Conditioning Using a Westrup LAH Brushing Machine
Duration – 1, 2 or 3 minutes Water Activity – 0.55, 0.65, 0.75 or 0.85 aw
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Damaged Caryopses after Seed Conditioning with Brushing Equipment
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Abrasion of Seed Covering Layers after Seed Conditioning with Brushing Equipment
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Percentage Broken Caryopses in Relation to Water Activity and Brushing Times
02468
1012141618
0.55 0.65 0.75 0.85
Brok
en c
aryo
pses
(%)
Water activity (aw)
LSD @ 5% = 1.96 1 minute
2 minutes
3 minutes
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65
70
75
80
85
90
95
100
0.55 0.65 0.75 0.85
Nor
mal
see
dlin
gs (%
)
Water activity (aw)
1 minute
2 minutes
3 minutes
71% c 79% b 84% a 82% a
The Effect of Aw and Brushing Times on Percent Normal Seedlings
83% a 78% b 76% c
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The Effect of Aw and Brushing Times on Percent Abnormal Seedlings
4
6
8
10
12
14
16
0.55 0.65 0.75 0.85
Abno
rmal
seed
lings
(%)
Water activity (aw)
1 minute2 minutes3 minutes
8% c 11% b 14% a
9% b 12% a 11% ab 12% a
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The Effect of Aging of Caryopses and Spikelets at 30 ˚C and 50% RH on Percent Normal Seedlings
Raw Pelleted
Film coated Encrusted 0
102030405060708090
100
1 2 3 4
Nor
mal
seed
lings
(%)
Aging period (months)
CaryopsisSpikelet
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Conclusion
• A brushing machine that is routinely used in seed conditioning was effective in extracting caryopses
• Increasing water activity level before brushing protected big bluestem caryopses from the detrimental effects of brushing and caryopses quality was significantly improved
• Moreover, the resulting caryopses were free flowing so could be sown in conventional planting equipment
• Caryopses and spikelets showed similar ageing trends thus brushing did not negatively impact longevity
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• Water activity measurements have a great utility to asses seed moisture level in all seed crops, but are particularly useful for chaffy grasses
• Following methods can be used to adjust water activity – aw to aw method - start with relationship of water added to aw, then
use quadratic equation to calculate the amount of water to increase sample to desired aw
– aw to seed mc method – start with moisture isotherm, then convert aw
to seed mc – empirical method – add varying amounts of water to different samples,
then measure aw – RH equilibrium method – use saturated salt or glycerol / water
solutions to provide desired RH [for small or research samples]
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Acknowledgements
Caryopsis extraction from big bluestem spikelets (Andropogon gerardii ) with seed conditioning equipment: Optimal water activity for recovery and seed quality. S. KAVAK and A. G. TAYLOR Published in Seed Science and Technology in 2013 (41, 60-72)
• The Scientific and Technological Research Council of Turkey (TUBITAK) and Cornell University for financial support of Dr. Suleyman Kavak’s sabbatical study at Cornell.
• Ernst Conservation Seeds (Meadville, PA) provided big bluestem seeds
• Kubtec (KUB Technologies, Inc., Milford, CT) prepared X-ray images.
• Technical support was provided by Sarah Pollicove, Ed Marino and Kyle Arvin during the course of this research.