There are seed banks all around the world that store seeds to preserve the genetic diversity of agricultural crops as well as rare or imperiled wild plant species. The most famous seed bank is the Svalbard Global Seed Vault, or “doomsday vault,” buried beneath the permafrost of a Norwegian island in the Arctic Ocean. Although the Garden’s seed bank might not be this sophisticated, the seeds are still stored at low temperatures in moisture-controlled environments, and are used in research that will benefit the conservation of desert species.
In 1966, Desert Botanical Garden started a seed bank, motivated by conservation, which is one of the pillars of the Garden’s mission. This seed bank, containing more than 4,000 accessioned seeds, has allowed the Garden to conserve plants by banking their seeds. Some seeds are collected from plants in the Garden, but most of the seeds added to the bank are collected from the wild by research staff and volunteers.
“Plants from the wild have much greater genetic diversity than cultivated plants. It is this diversity that we want to capture when collecting seeds from the wild,” says Steve Blackwell, conservation collections manager. “The wider the range of genes we collect from a population, the greater chance the collection has of harboring those traits that will help a species survive threats such as climate change.”
Seeds are collected from the plant after it has finished flowering, requiring strategically planned collection trips. While removing seeds is not harmful to the plant, permits are still required for most areas in Arizona. When collecting seeds from rare plants, only 10% of the plant can be collected to ensure it can continue to reproduce and to not further deplete the population.
Once a seed is collected, there is a process for adding it to the Garden’s seed bank:
- Seeds are collected and transported in paper bags to begin the drying process.
- Research volunteers clean the seeds by hand, – separating them from the other plant material or extracting them from their fruit.
- Seeds, along with their collection data, are accessioned and added to the Living Collections database.
- Seeds are dried down to 20% humidity, sealed in air-tight pouches and put into a freezer at -20 degrees Celsius (-4 F).
In addition to banking the seeds, base germination rates and percentages are collected on all species. Technically, a seed is considered germinated when 1-2 millimeters of the root emerges from it. To collect this data, three groups, or replicates, of seeds are put on a damp paper towel or sand substrate in a germination chamber at a standard temperature and light regime. Seeds are monitored to determine how quickly and how many of them germinate over time. After the seeds have been stored for a certain amount of time, they are tested again to determine if their germination rate has changed.
“This research is conducted to determine the best practices for storing different kinds of seeds. Some seeds will not survive if they are frozen, while others need to be stored at different temperatures,” explains Blackwell. “When a new species has not been stored, it is this research that can help us determine the best method of storing the seeds to get the best chance of maintaining their viability.”
The seed bank has created additional opportunities for the Garden to take part in national conservation efforts. As a member of the Center for Plant Conservation (CPC), the Garden is tasked with conserving 52 rare and endangered plants that range from south Texas to California. Seeds are collected from these plants and stored at the Garden, while a backup collection is sent to the National Laboratory for Genetic Resource Preservation in Fort Collins, Colorado. It is a team effort to preserve the genetic diversity of plants, and the Garden is a partner in conserving U.S. flora, specializing in the deserts of the Southwest.
There are plans to expand the seed bank to the new Horticulture Center, which is scheduled to open in March, 2017. The seed bank’s new location will have germination chambers that will allow for the regulation of light, temperature and humidity to standardized conditions. The current Seed Photography Lab will also be relocated along with the seed bank, with the goal of photographing the seeds of every species in the collection.
“With the expanded space, the Garden can further add to its seed collection and continue to be a leader in the conservation of desert plants,” says Blackwell.