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Researchers Warm to the Chilly Truth About Winterfat Seeds

By Don Comis
January 28, 1999

Most people wouldn't give the winterfat shrub a second look--assuming they noticed it at all. But in winter this humble native plant can be a life-saving forage for cattle, deer, antelope and elk. In summer, it provides cover for nesting ducks on the Canadian prairie.

But what intrigues researchers about winterfat is the seeds' ability to germinate even after "daggers" of ice crystals form in the embryos. These crystals quickly kill embryos of most domestic plants.

Could winterfat's ice tolerance be transferred to crop plants? Researchers don't yet know. But they have found that its seeds will germinate and grow after cycles of wetting, freeze-drying at sub-zero temperatures and re-wetting.

Rangeland scientist Terry Booth, who works for USDA's Agricultural Research Service at Cheyenne, Wyo., speculates that the freeze-drying occurs because of ice crystals on the seed's hairy outer layer. These crystals may suck water from the embryo, helping keep it dry and preventing large, destructive crystals from forming inside it.

In highly magnified photographs of winterfat seed cells frozen to minus 22 degrees F, ice crystals show as dark holes in the embryo.

ARS, the chief research agency of USDA, operates the High Plains Grassland Research Station at Cheyenne.

The Bureau of Land Management, USDA's Forest Service and mining companies plant winterfat on degraded rangelands and strip-mined areas. Booth's experiments have shown that winterfat plants evolved differently in their freeze tolerance to adjust to local climate. This suggests it is generally best to plant winterfat seeds collected locally.

Winterfat seeds are not the only plant seeds that survive with ice in their cells. But in the animal world, this distinction is known to be held only by a nematode, a microscopic roundworm, in Antarctica.

A story about the winterfat research appears in January's Agricultural Research magazine and also is on the World Wide Web at:


Scientific contact: D. Terrance Booth, ARS High Plains Grasslands Research Station, 8408 Hildreth Rd., Cheyenne, WY 82009-8899, phone (307) 772-2433, fax (307) 637-6124,