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Reading snow waves.

When temperatures begin to fall and the skies turn gray foretelling the coming winter, plant physiologist C. Robert Olien takes to the air to track the growth of his fall-planted barley.

Olien's interest in aerial observation is helping him identify barley plants that show the best winter-hardiness, or ability to withstand the bitter cold of the northem United States. The information will be usefut to plant breeders who want to build superior cold-hardiness into crops.

Once a week during the winter, Olien, who is in the ARS Sugarbeet, Bean, and Cereal Research Unit at East Lansing, Michigan, takes aefial photographs of the wavelike snow and ice pattems that cover his test plots. He uses a 35mm camera with a 50mm lens at altitudes from 500 to 1,000 feet.

"At first I tried charting everything by hand while standing on top of my car, but that just wasn't high enough," says Olien.

A colleague suggested erecting a pole that Olien could climb to get a better view of the snow-covered fields. But in the end, he decided that the best vantage point would be from an airplane: the best record, a photograph.

Daily high and low temperatures limit geographic distribution and productivity of plants. These limits, in tum, define the choices of crops that producers in the northem United States can grow.

Barley and other cereal crops that are planted in the fall, emerge and grow. Their ability to survive the winter vaiies depending on their ability to adapt to changes in the environment.

Plants' winter hardiness is influenced by the presence of freeze inhibitors, known as arabinoxylan mucilages, that interfere with the forrnation of ice crystals.

To maintain winter hardiness, a plant needs energy from photosynthesis. But in cold weather, buried under snow, the energy must come from stored sources. Sucrose, glucose, and fructose, along with the oligosac- charide fructan, are the primary energy reserves for cereal grains, he explains.

As winter progresses, several stress sequences occur. Each stress requires different biochentical activity to protect the plant and enable it to survive. The plants also need a snow cover to insulate against severe cold temperatures.

Recovery and regrowth of the plants in the spring depend on survival of the crown meristem, the growing point of the plant just above the soil surface.

Olien found that ever-changing pattems of the snow and ice cover play a role in the variation of winter injury of a cultivar. The wavelike snow and ice pattems are partly due to topography of the field and drifting as the snow falls. "But in a relatively unifon-n field, wind and sun are the major factors," he says.

These patterns affect not only the condition of the plants beneath, but also the form and intensity of the stress that may lead to injury. Erosion of the snow and ice tends to induce changes in the chemical makeup and physical condition of the plant. But if the changes do not occur, the plant's susceptibility to injury increases as conditions become even more severe.

"Winter killing in Michigan is most likely to occur during low-temperature stress after a midwinter thaw, when crown tissues have a high moisture content," says Olien. Freeze injury typically occurs in a sequence of several thaw-freeze cycles. Other major fortns of freeze injury are caused by adhesion and-under the most severe conditions-by freeze dehydration.

Olien superimposes several negatives of photos taken as winter progresses, to view the total effect of the variable environmental conditions.

He also compares plants from the field to those grown under controlled freeze conditions in a laboratory growth chamber. And he examines tissue sainples from both the field-and lab-grown plants.

Plants that prove to be the hardiest are tagged for use in breeding programs to improve the winter-hardiness of cereal crops.

"Ideally, we want to combine the best genes with the best management tools to get a quality product and high yield," says Olien.-by Marcie Gerrietts, ARS.

C. Robert Olien is in the USDA-ARS Sugarbeet, Bean, and Cereal Research Unit, Department of Crop and Soil Science, Michigan State University, East Lansing, MI 48824-1325. Phone 517) 355-2233, fax number (517) 353- 5174.
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Title Annotation:snow and ice patterns on crop fields
Author:Gerrietts, Marcie
Publication:Agricultural Research
Date:Nov 1, 1992
Words:691
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