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

Big Bluestem (Andropogon gerardii Vitman)

• Perennial, warm season grass • Used as a forage for livestock, soil conservation and as a feedstock for biofuel

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

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˚

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

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

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)

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)

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

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

Damaged Caryopses after Seed Conditioning with Brushing Equipment

Abrasion of Seed Covering Layers after Seed Conditioning with Brushing Equipment

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

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

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

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

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

• 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]

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.