Soybean plants make a mighty defense against dry and hot weather as they attempt to grow a seed crop this summer. Each soybean may bring a different combination of traits to the battle.
Felix Fritschi, a University of Missouri plant scientist, examines plants in his plots to find winners—and losers—in the 2012 summer weather. He's looking for drought tolerance in farm crops.
Some send roots deep into the soil, seeking water. Others turn their leaves different directions to reduce solar absorption and keep cool. Fritschi, a plant physiologist, studies differences in plant traits among varieties.
"Plants are stressed by one of the driest summers on record, but also one of the hottest," Fritschi says. Those are different stresses. Plants put up different defenses for each.
Adding to stress is low relative humidity. That speeds water loss from stressed plants.
Fritschi showed examples of how plants react to multiple stresses at the annual two-day Crop Injury Clinic on the University of Missouri Bradford Research Center east of Columbia, Wednesday.
Certified crop advisors (CCA), agronomists that work for farm service companies and MU Extension, learn new research results to upgrade their skills. They earn continuing education credits.
"Each variety copes in slightly different ways," Fritschi says. "That gives me something new to consider."
In a small area of his plots, one plant may be green and thriving. A nearby plant wilts in the heat. A third variety died early from drought.
Farmers now see their soybeans shedding blossoms to save energy. Or, if further along, they abort seed pods. If pods did set, they may have one seed instead of three or four. Those are defenses in a fight for survival.
The physiologist studies each plant to find those differences. Likely, there are multiple traits at work. These may include how wide or narrow the stomata openings are on the underside of the plant leaves. The stoma allows carbon dioxide (CO2) to enter from the atmosphere. When that window opens moisture escapes.
"If you could find a way for plants to take in CO2 without losing water you would have a drought-resistant variety," Fritschi told crop advisors. Already he knows that some stoma open wider while others close quicker under stress.
As a physiologist, Fritschi identifies traits that make each plant variety different. His results will be turned over to plant breeders to bring together varied stress-coping traits into new varieties.
One by one, Fritschi examines varieties from the U.S. Department of Agriculture Germplasm Collection. This seed bank in Illinois maintains thousands of seeds from around the world to test. They may give new clues to drought and heat tolerance.
It's a complex job. Roots and leaves respond to stress in different ways. To gather sun rays, which drive photosynthesis the process of converting CO2 into plant biomass, some plants turn leaves broadside to the sun. That process shifts all day long, as the sun arcs across the sky. They face east in the morning and west in the evening.
"If you look across a bean field this summer and it appears silvery instead of dark green, the leaves are protecting the plant," Fritschi says. The white undersides of bean leaves are tipped up to reflect the sun. That's another defense."
There's much more. Hundreds of variables go into plant survival.
Corn leaves roll tight to reduce sun exposure, collecting less solar energy. Also, relative humidity will be
higher within the roll of leaves, slowing transpiration.
"Different soils and different plants interact in different ways," Fritschi says. "Plants on clay-pan soils at Bradford face different challenges than plants on sandy loam at the river a few miles away."
Sandy soils give plants little time to adapt from moist to dry conditions. Clay soils hold moisture ten times longer, allowing more adaption time. Different plants react at different speeds.
"From what we've learned so far, plant breeders may offer different varieties for different soils," Fritschi predicts.
Of the 591 acres on Bradford Farm, Fritschi uses only a small area under his research rain sheds. He controls the environment over his plants protecting them from rain.
In the second year of his research the weather supplies ample stress to study.
Bradford Research Center, one of 20 MU farms across the state, is part of the Agricultural Experiment Station of the MU College of Agriculture, Food and Natural Resources. The farms provide local research results to extend to area farmers.
Source: University of Missouri Extension