Seed Longevity in
the California Flora
Evan P. Meyer
Rancho Santa Ana
Botanic Garden
Claremont, CA
Chorizanthe orcuttiana. Credit: John Macdonald
How long do seeds live?
• There is not a simple answer…
• Most work has been done on agricultural species
• Seed longevity knowledge of wild species has
practical applications in restoration, horticulture,
seed bank management and theoretical
importance in ecology and plant reproductive
biology
Xylorhiza cognata. Credit: John Macdonald
Modeling Seed Longevity
• Developed in mid 20th century to predict storage
life of crop species
• Seed Viability Equations (temperature, moisture,
*species specific constants*, genotype, prestorage conditions)
• Seed survival curves
• This has led to the development of best
practices
Seed Banks
Svaldbard Seed Vault, Norway
National Center for Genetic Resource
Preservation (NCGRP), USA
Traditional Seed Bank Storage
Protocols
• Seeds dried to low moisture content
• Seeds stored in freezers (-18 to -23° C)
Seed Storage Behavior Types
•Orthodox
•Intermediate
•Recalcitrant
Acer macrophyllum. Credit: Neil Kramer
Clarkia breweri. Credit: Neil Kramer
Quercus durata var. gabrielensis. Credit: Naomi
Fraga
Empirical determinations
• Germination assays
• Tetrazolium (TZ) testing
Centromadia parryi ssp. australis
germination assay. Credit: John Macdonald
Suaeda nigra TZ test. Credit: Annette
Miller
Credit: John Macdonald
A Long Term Test of Seed Longevity
Fritz Went and Philip Munz
• Initiated in 1948
• 113 California native taxa
stored at extremely low
humidity in glass tubes at
ambient room temperature
• Germination testing every
20 years
• Follow up testing to occur
until 2307
Data are averaged for 70 species showing > 0 germination
Average % Germination
50
seeds stored in
vacuumed-sealed vials
40
30
Vials opened and
seeds stored at
ambient in Pasadena
20
10
Vials opened and seeds
stored at ambient in Ft.
Collins
0
0
25
50
75
Average Seed Age (years)
Slide provided by Chris Walters, NCGRP
After 66 years of storage…
•Only 3 taxa had a > 15% drop in
germination %(Leptosyne bigelovii, Clarkia
amoena and Eschscholzia californica [var.
crocea])
•In the same time period, 27 taxa had a >
15% increase in germination %, 4 with
>50% increase (Parksinsonia microphylla,
Phacelia viscida, Achillea millifolium and Gilia
achilleaefolia)
RSABG germination database
•
•
•
•
4800+ germination trials
1500+ taxa
500+ genera
All incoming accessions are tested, as much
follow up testing as possible
Comparison of age classes
• 1103 tests with ≥ 10
year old seed
• 3500 tests with < 10
year old seed
Comparison of age classes
• 1103 tests with ≥ 10
year old seed
• Average seed age is
15.76 years
• 3500 tests with < 10
year old seed
• Average seed age is
2.26 years
Comparison of age classes
• 1103 tests with ≥ 10
year old seed
• Average seed age is
15.76 years
• Average germination
is 43.13%
• 3500 tests with < 10
year old seed
• Average seed age is
2.26 years
• Average germination
is 43.48%
Comparison of age classes
• 1103 tests with ≥ 10
year old seed
• Average seed age is
15.76 years
• Average germination
is 43.13%
• 206 tests with 0%
germination (19%)
• 3500 tests with < 10
year old seed
• Average seed age is
2.26 years
• Average germination
is 43.48%
• 406 tests with 0%
germination (12%)
Comparison of age classes
• 1103 tests with ≥ 10
year old seed
• Average seed age is
15.76 years
• Average germination
is 43.13%
• 206 tests with 0%
germination (19%)
• 3500 tests with < 10
year old seed
• Average seed age is
2.26 years
• Average germination
is 43.48%
• 406 tests with 0%
germination (12%)
Using ≥ 5 years as the cutoff yields the same results!
(no significant difference in germination percentage)
1
Average Germination
Percentage by Genus
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
<10 year old germ %
≥10 year old germ %
In conclusion…
• Averaging all taxa, we haven’t seen significant
declines in germination % during the time that
seeds have been seed banked
• We need to take a closer look at taxonomic
trends in zero viability collections
• More collections will allow us to gain a better
understanding of longevity of the entire flora
(less than 25% of taxa are currently in seed
banked collections)
Future work
• Aggregate other data sets
• Targeted germination tests to expand the
RSABG data set
• Tetrazolium testing
• More thorough analysis
• Classify intermediate species
• Publish!
Acknowledgments
Chris Walters and the NCGRP staff, Michael
Wall, John Macdonald, and the many collectors
who have contributed to the RSABG seed bank.
Thanks!
[email protected]
Ventana Wilderness. Credit: Billy Sale
The preceding presentation was delivered at the
2015 National Native Seed Conference
Santa Fe, New Mexico April 13-16, 2015
This and additional presentations available at
http://nativeseed.info