Wyoming Big Sagebrush
Germination After 2 Years
Storage in Sealed Containers
Storage of Sagebrush in Sealed
Containers –Why?
• Sagebrush seeds are relatively short lived
• Genetic conservation via long term
(decades long) seed storage
• Have seed sources on hand for
emergency rehabilitation
• Preserve seed viability in multiyear
collections needed for common gardens
and other genetics work
Methods
• Seed Moisture
– Equilibrium relative humidity (ERH)
– Adjusted seeds to 30, 40, 50, 70 ERH
• Storage Temperature
– -20o, -8o, 3o, 20oC
Humid air (70%)
Water
moves
both ways
or not at
all.
Moist Seed
The condition of a high equilibrium relative humidity. At
equilibrium this seed will measure an ERH of 70%.
Dry air (30% relative humidity)
Water
moves
both ways
or not at
all.
Dry Seed
The condition of a low equilibrium relative humidity. At
equilibrium this seed will measure an ERH of 30%.
Hygrometer measuring ERH of seeds in a covered box
Probe
Sample holder
A water activity (Aw)
meter used to measure ERH.
Meter
Water
Activity
Meter
Wyoming Big Sagebrush Isotherm
Artemisia tridentata ssp wyomingensis
16
y = -2E-05x 3 + 0.006x 2 - 0.2913x + 10.65
R2 = 0.9636
Moisture Content %
14
12
10
8
6
4
2
0
10
20
30
40
50
ERH %
60
70
80
• Why use ERH and not moisture content?
Key points of ERH
 Can be used on any seed lot regardless of
 Viability
 Purity
 Stage of extraction
 Species
 No conversion charts needed
 Traceable standards available for calibration
 Non destructive
 Fast – Results obtained in a few minutes
 Very easy to use
 Low cost equipment ($200 to $2500)
Seed Lots Used in the Tests
• 5 commercially collected seed lots
– Part was cleaned to a “high purity”
– Part was left at the low purity condition
supplied by the vendors
• Each lot was mixed in a riffle seed divider
to ensure uniformity among subsamples
– 4 fractions each, one for each ERH
– Each ERH Fraction again divided with the
riffle divider into 4 fractions , one for each
temperature
Containers
• 16 fractions (4 ERH x 4 Temps) sealed in
6 mil poly bags for each of the 5 seed lots
– 80 bags of seed
• 2 fractions (30 and 40 ERH) for each of
the 5 seed lots was sealed in a foil
laminate bag
– 10 foil bags
– Done to see if this might be a better container
– This is the foil bag used at NCGRP
Sagebrush Seed Storage Lot WP High Purity Seed
3 months
30
40
50
70
Blank
-20
-8
2
Storage Temperature C
20
%
70
60
50
40
30
20
10
0
ER
H
% Germination
Initial
germination
was 56%
Sagebrush Seed Storage Lot WP High Purity Seed
6 months
Initial
germination
was 56%
60
40
30
20
50
0
70
Blank
-20
-8
2
Storage Temperature C
20
%
40
ER
H
% Germination
80
Sagebrush Seed Storage Lot WP High Purity Seed
15 months
Initial
germination
was 56%
60
40
30
20
50
0
70
Blank
-20
-8
2
Storage Temperature C
20
%
40
ER
H
% Germination
80
Germination at 29 months, High
Purity Seeds, Average of 5 seed
lots
Number of Seedlings per Gram
Sagebrush Seed Storage Low Purity Lot CA2
6 months
Initial
germination
was 48
seedlings per
gram
100
50
30
50
0
70
Blank
-20
-8
2
20
Storage Temperature C
Number of Seedlings per Gram
Sagebrush Seed Storage Low Purity Lot CA2
15 months
Initial
germination
was 48
seedlings per
gram.
100
50
30
50
0
70
Blank
-20
-8
2
20
Storage Temperature C
Number of Seedlings per Gram
Sagebrush Seed Storage Low Purity Lot CA2
29 months
Initial
germination
was 48
seedlings
per gram.
100
50
30
40
50
0
70
Blank
-20
-8
2
20
Storage Temperature C
ERH %
Findings
Low Purity Seeds
• Cleaning the seed appears to make it live
longer in seal container storage.
• If the seed is not cleaned it must be at
30% ERH and frozen when put in sealed
containers.
Findings
High Purity Seeds
• Storage in foil bags at -20oC was the best
condition in this study
– ERH was maintained well in both poly and foil
bag
– Does the effect of the foil bag go beyond
superior moisture barrier?
• 30, 40, and 50% ERH were equivalent in
preserving germ at 29 months of storage
• -20oC was the best temperature