Stashing seeds in 'Noah's fridge'

Researchers worldwide are collecting seeds from wild plants to guard against the ravages of climate change.

from the June 13, 2007 edition

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The ins and outs of seedbanking

Careful drying and storing can reliably hold seeds in suspended animation for at least two centuries. The real challenge is ensuring genetic diversity. Without it, scientists will have a harder time reestablishing viable plant populations in the wild.

At San Diego Zoo's Conser­va­tion and Research for En­­dan­gered Species, scientists typically collect seeds from at least 100 individual plants of the same species. That's enough, they estimate, to preserve 98 percent of a species' genetic diversity.

The most comprehensive collections include seeds from different years. By gathering seeds from different seasons, scientists know that their seed collections contain any variations that might lead a variety of plant to prefer hot over cold, wet over dry, and vice versa.

While in the field collecting, scientists jot down information on the surroundings. Was the plant in the shade, on a hill, near a stream? Once in the lab, scientists expose some seeds to various combinations of moisture, daylight, and temperature to determine their ideal germinating conditions. All this information goes into a database to help guide future restoration efforts.

The remaining seeds are dried for up to several months. Once desiccated, the seeds go into insulated silver pouches and, eventually, refrigerators where they'll be kept at minus 20 degrees C (minus 4 degrees F.). In these conditions, seeds can last up to 500 years.

In all, "securing a species" costs some £2,000 (almost $4,000), says Michael Way, the Americas coordinator in the seed conservation department of the Kew Royal Botanical Gardens, which houses Britain's Millennium Seed Bank Project.

Collections at the MSBP, which can reach more than 15,000 seeds per species, average about 3,500 seeds. But if the number of seeds dwindles for any reason, the seed bank may replenish it by growing plants in greenhouses. Scientists prefer not to, however. Greenhouse conditions could generate plants that thrive in "unnatural" conditions, traits that might work against the species in the wild.

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