seed bank

Authors: Stacy Anderson, Tobin Weatherson, Joe Davitt - San Diego Zoo Native Plant Seed Bank

We are all taught in school that water expands when frozen. That's why ice floats, sealed bottles explode in the freezer, and frost kills living tissues. All living cells are comprised largely of water and can rupture and die when the water they contain expands under freezing conditions. The cells of seeds are no different.  Research has shown there is a "goldilocks zone" of relative humidity that our seeds must reach before freezing. This perfect range of relative humidy is greater than 25% and less than 35%. The final and most crucial step before freezing our seeds, is testing their relative humidy to ensure it lies within this range. At SDZGs native plant seed bank we use small air tight desiccation chambers and color changing silica gel to obtain the relative humidity needed in our seed accessions. It's also common to use salt solutions to desiccate. We have found that a very quick and convenient way to read the relative humidy is to place a BlueMaestro Tempo Disc inside our sealed chambers. Given amble time to stabalize, we can infer the seeds reach an equalibrium with their ambient environment. These discs can quickly tell us the relative humidy inside the desiccation chambers without opening them and exposing the contents to humid air. There is a simple app on our phones that gives us temperature and relative humidity levels, and makes it easy to track these data over time. It's important to note that the size of the desiccation chamber, the amount of silica or salt solution, the number of seeds, and the type of seeds can all affect the time it takes to reach equilibrium (within a sealed chamber). For a more precise relative humidity measurement, or if we are unsure about the equilibrium within a chamber, we use The Rotronic HygroPalm. This hygrometer is also useful for obtaining a baseline RH reading from fresh seeds. The HygroPalm uses a small cup to measure the relative humidity of a sample.We attach the probe to the connection port, and turn it on by pressing the red button. We fill this small cup to the line with seeds and the probe tightly covers the sample. It then slowly draws in air and in about 5 minutes gives a very accurate reading. Note some of the drawbacks of using this hygrometer. Sometimes we have very small amounts of seeds in many maternal lines that we can not combine. We don't always have a large enough sample for this cup. We also have to open our chambers and disrupt equilibrium to test. For this reason, we use both the ibuttons and the hygrometer. We have designated desiccation chambers that are very stable and hold small accessions that stabilize quickly, and others for large bulked accessions. We always open and close these chambers as quickly as possible.  When we know that it is safe to freeze the seed, we place the accession into foil lined bags and heat seal them. The bags are now ready to freeze for long term storage, where they can survive for hundreds or even thousands of years, be preserved for generations to come and act as a safe guard against extinction.

Date Recorded: 
Wednesday, October 14, 2020

Alexandra Seglias (Denver Botanic Gardens)

Nicola Ripley (Betty Ford Alpine Gardens)

Brittany Roberts Marshall (Betty Ford Alpine Gardens)


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Alpine ecosystems are particularly vulnerable to climate change. The Denver Botanic Gardens are seeking to protect rare species from these regions, banking seeds from multiple Alpine populations by maternal line. However, collecting seed from these remote areas comes with multiple challenges. Seed production is dependent on the previous year's winter weather, there is a short window for flowering and seed setting, the phenology changes rapidly, and many sites are difficult to reach.
After gathering seed, researchers at Denver Botanic Gardens perform germination trials and grow seedlings to be reintroduced. Plants are also added to the living collections at Denver Botanic Garden and the Betty Ford Alpine Botanic Gardens to further preserve these rare species.

Contributing Author(s): 
Date Recorded: 
Thursday, May 21, 2020

Dr. Johnny Randall, North Carolina Botanical Garden

The infamous Venus flytrap, Dionaea muscipula, found across North Carolina and into South Carolina, has been seen to be declining in recent years. It is currently under review for federal listing, is ranked G2 on NatureServe, and considered vulnerable by RedList. Threats to this charismatic plant include poaching, trampling, and changes in fire and hydrology. Dr. Randall of the North Carolina Botanical Garden is conducting a double-pronged conservation effort, collecting and banking seeds by maternal line, and doing genetic analysis across the populations. Results from the genetic data suggest four distinct clusters that closely match phylogeographic areas.

Contributing Author(s): 
Date Recorded: 
Wednesday, March 4, 2020

Joe Davitt, Institute for Conservation Research, San Diego Zoo Global

Maintaining a plant species’ genetic diversity can contribute to adaptive potential, prevent inbreeding effects, and potentially preserve traits such as drought tolerance and disease resistance, all of which are critical in a changing climate. Seed collections are often the best method of conserving the genetic diversity of rare plant populations ex-situ, however most seed collections are made with no available genetic data from the target species. Ideally, this genetic data would give us a clear picture of which populations are the most critical to conserve and how genetically structured a species’ populations are in relationship to one another, but this can be a time consuming and costly process. Seed collection protocols, such as those published by the Center for Plant Conservation, can inform our general best practices, but as seed collectors we must also infer best practice on a species by species basis. The life history and reproductive biology of the target species, as well as our sampling methods can greatly impact the effectiveness of seed collections to capture the entire target populations’ genetic diversity. Taking all available information about a species into consideration, we can infer the best seed collection methods to ensure genetic conservation.

Contributing Author(s): 
Date Recorded: 
Tuesday, September 10, 2019

Seed bank databases - what do you use?

We have been housing our seed bank and living collections data in Microsoft Access, but are looking to change. Our Horitculture team is interested in IrisBG, but I have no idea how well that would work for housing our seed bank accessions. What are folks using to manage their seed bank databases? I want to implement something that is user friendly and nimble enough to house all of the different types of data we record. We don't have a budget for this at this time, but I'm open to fee-based options if they are much more powerful than free databases.

Question Category: 

Foil vs. plastic pouches for seed bank storage

We have used both foil and plastic vacuum sealed pouches for packaging glassine envelopes prior to storage in the seed bank freezer. Are there major advantages to foil vs. plastic? We have used foil historically, but have also used plastic. The benefits to plastic that I see are not just that it is cheaper, but also that you can customize the size of your pouch more easily. Sometimes we have a very small collection and don't need a full foil pouch and sometimes if we have bulky seeds, it's helpful to make a slightly bigger pouch.

Question Category: 

Vanessa Handley, University of California Botanical Garden

University of California Botanical Garden (UCBG) has long been engaged in recovery efforts for State and Federally endangered large-flowered fiddleneck, Amsinckia grandiflora. Initially UCBG staff focused on creating a substantial seed bank for the species and, through nursery augmentation of wild-collections, generated a bank of over 100,000 seed (stored along maternal lines). In 2016, a subset of this seed was deployed for a large-scale reintroduction effort at three sites in San Joaquin County, California. The reintroduction was conducted in partnership with Vollmar Natural Lands Consulting (with funding from the U.S. Bureau of Reclamation) and entailed cultivation and outplanting of over 4000 seedlings. This endeavor - made more challenging by severe terrain and freezing winter rains - resulted in modest persistence in 2017, followed by a banner spring in 2018. UCBG staff and volunteers completed a supplementary round of outplanting this past winter and, by March, all three introduction sites were awash with orange - the Amsinckia grandiflora Super Bloom! This exciting outcome was potentiated by engagement of diverse stakeholders: environmental consultants, multiple agency partners, public and private landowners and UCBG. While the taxon still has a long path to recovery, this preliminary success is a testament to the power of these partnerships. Our recovery implementation strategy will be discussed.

Contributing Author(s): 
Date Recorded: 
Friday, May 3, 2019

Insurance for Seed Bank?

I'm curious if others have insurance policies for their seed banks. Our herbarium collection has additional insurance so it seems like seed collections could as well. Does anyone have additional insurance for their seed collections? How do you apply value to your collections?