People who want to save and protect their money may put their funds in a bank. The same is true with samples of the seeds that produce the world’s favorite foods.
These safe places are called genebanks, for the simple reason that they are storage places for genes, the genetic material that gives plants and animals (and humans, as well) their identities. There are about 1,500 such places around the world that specialize in ex situ conservation of plant material. “Ex situ” refers to keeping samples of seeds and other material in places outside their normal habitat — often in securely-built facilities that offer storage at bitterly cold temperatures and low humidity. The lower the temperature and humidity, the longer the seeds will remain viable (capable of living) once they are removed from storage and warmed up again.
It’s the same principle as buying chicken or frozen vegetables and placing them in the freezer at home. The foods would spoil if left at room temperature for an extended time, but they'll keep for longer periods if frozen. You’d remove the chicken or vegetables from the freezer and thaw them before cooking and eating them. The difference with seeds is that, once they are thawed out, they may be used to produce many more generations of plants and seeds.
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| Genes in the bank. Samples of plant germplasm are placed in short-, medium- and long-term storage in several ways. The U.S. National Plant Germplasm System stores some plant material in containers on shelves (far left); other material goes into drum-like vats of liquid nitrogen for very long-term storage (center). Both are in a super-strong building in Fort Collins, Colorado. The International Potato Center (CIP) in Peru stores living potato germplasm in vitro — that is, in test tubes containing liquid nutrients. (USNPGS by Fred Powledge; CIP by International Potato Center.) | ||
The United States’s National Plant Germplasm System, one of the world’s leading genebanks, has around 500,000 plant samples in its facility on the campus of Colorado State University, in Fort Collins, Colorado. The building’s walls are 12-inch reinforced concrete, the inner doors are like those in a bank vault, there are numerous security systems and backup refrigeration units, and the roof is made of steel plates just in case something heavy falls on it. The building’s operators say it can withstand fires, tornadoes, earthquakes, and terrorism. When the Cache la Poudre River flooded the college campus a few years back, the seed bank and its contents were unscathed.
Two old refrigerators.
At the other end of the
scale, in Coventry, England, Ryton Organic Gardens has a genebank that
consists of two very old refrigerators. It’s
used to store local plant varieties. Elsewhere around the world are hundreds
of thousands of samples (“accessions,” as they are known) of
rice, wheat, maize, peppers, coffee, chickpeas, soybean, cassava — you
name it.
Some species, which do not produce normal seeds or do not do well in regular genebanks, are kept alive in vitro. This is Latin for “in glass.” Usually in a genebank this means in a test tube or other small glass container, with liquid nutrients. Such plants must be attended to frequently to keep them well-fed and to make sure they don’t outgrow their containers. So keeping plant material viable ex situ does not mean just filing it away and forgetting about it.
Temperatures in the regular genebanks very, depending on how long scientists want their seeds to remain viable. Low humidity is very important, too. Seeds stored at 20 degrees C and between 30 percent and 40 percent humidity are considered in “short-term storage.” If the temperature drops to 4 degrees C and the humidity is brought down to 20 percent, the seeds might be expected to last for 15 to 20 years and remain viable. Researchers remove samples of seeds from storage from time to time and “plant” them — grow them in warm ovens — to test their viability.
For truly long storage, researchers are using cryopreservation (“cryo” refers to very low temperatures). Typically, seeds are stored in vats, resembling kettle drums, that use liquid nitrogen at a temperature that can reach minus-196 C. At this temperature, virtually all chemical changes in the seed grind to a halt. But they can be reversed once the seed is thawed out.
Why go to all this trouble to conserve germplasm ex situ, when it can be conserved in situ? The answer is environmental erosion and its close relative, genetic erosion. Many of the places where foods and their wild relatives grew are no longer available for plant life, and the ones that do remain are under near-constant danger. They have given way to single-species agriculture, or development that flattens forests and paves the soil. Now, many collectors think, the safest place for plant germplasm is inside a securely locked genebank.
A drawback.
There's a drawback to all this protection. As we learned in the page
on in situ storage, one advantage
to plants growing in the wild is the fact that they, like the rest of
us, grow in reaction to their
environment. They evolve (or the fittest of them do) to coexist with
changes in climate and other environmental factors.
This doesn’t happen in ex situ conservation. If a seed comes out of cold storage after 20 years, it is the same seed it was 20 years before. If Earth’s climate has become warmer or wetter or drier or the plant’s natural enemies have become stronger, and the seed isn’t able to cope with those changes, it may be placed under great stress.
Consider how you’d feel if, like Rip Van Winkle, you fell asleep for a very long time. When you awoke, pretty much everything around you — methods of transportation, forms of communication, kinds of entertainment, and no doubt all computer software — would have changed completely.
Given the great amount of environmental change that is occurring nowadays (much of it for the worse), scientists agree that the best protection for germplasm, including the seeds of the plants we depend on for our daily foods, is a combination of methods. We need protected areas — parks, reserves, botanical gardens, arboretums — where plants can evolve in tune with nature, and we need those cold-storage facilities where samples of our most prized plants can be kept, ready to regenerate in the event of an emergency. We need both in situ and ex situ.
Seed morgues? With all that money invested in building genebanks and maintaining their special climate systems, you'd think that the seeds inside are pretty comfy and safe. Well, yes and no. Surveys of genebanks have shown that an alarming amount of the plant material inside the banks is useless. In some cases this is because the seeds have not been prepared and stored properly. In many other cases, the identifying material that accompanies the seeds is incorrect or incomplete. These “accession documents” (sometimes referred to as “passport information”) should contain, at the very least, data on when and where the plant material was collected, along with identifying characteristics (is the bean white, brown, or speckled?), notes on the ecological surroundings of the plant, and, above all, an identification number with which the material can be followed through the system. Often the number is represented by a barcode, just like groceries at the supermarket. Later, when the material is grown out in the lab, more information about its characteristics is added. Oftentimes, even these basic bits of information are missing. One crop scientist has complained that the seed banks holding these sloppily-maintained materials “are really seed morgues.” |
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