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WFU team digging into root systems of tomatoes
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Published: September 20, 2008
If you look over the hill at The Children's Home on Reynolda Road, you'll see what looks like just another late-season tomato patch. The plants are small and bedraggled, like most September tomatoes. They've been through the ringer of too-much and too-little rain, too-hot late and too-cold early. But these tomatoes bear a closer look.
If you look closer, you'll find that a serious investigation into the effect of ethylene on root development in tomatoes is under way down there.
A research grant
A professor of biology at Wake Forest University, Gloria Muday, and four students -- Kevin Cooper, an undergraduate; Poornima Sukumar, a graduate student; and Sangeeta Negi and Daniel Lewis, post- doctoral researchers -- are tending a garden of 168 tomato plants. They are funded through a grant from a branch of the USDA known as the Cooperative State Research, Education and Extension Service National Research Initiative on Plant Biology Growth and Development.
Two varieties of tomatoes are being grown, Pearson and Alisa Craig. Mutations of these two heirlooms have yielded plants that have developed a genetic change in the receptor for the hormone ethylene.
Ethylene is an important factor in the ripening of tomatoes. The production of ethylene increases further production of ethylene, and that is what causes tomatoes to ripen quickly. The mutation of Alisa Craig and Pearson, named Neverripe, produces fruit normally, but the fruit never matures and turns color. Another mutation, called Epinastic, produces too much ethylene and causes the cells on the top to grow faster than those on the bottom. These plants exhibit leaves with curled margins. Both of these mutations had been discovered in the past by other researchers in the field.
Profuse branching roots
The final mutation being studied is called pbr, shorthand for profuse branching roots and was isolated in India by Sangeeta Negi. It produces plants with increased numbers of lateral and adventitious roots. Roots are described as adventitious when they spring from the stem of the plant in great abundance.
Muday and her students are studying how two hormones, ethylene and auxin, might communicate to influence the growth habits of roots. The name of her grant is Ethylene and Auxin Crosstalk in Control of Root Architecture. The research has found that the Neveripe mutation produces extensive root systems.
If research can yield an understanding of the influence of these hormones on root growth, the potential for developing plants that can tap into deeper soils and absorb nutrients and moisture through a more extensive and prolific root system would be great. As the "non-technical summary" of the grant proposal puts it: "As agriculture expands into regions with greater limitations on moisture and nutrient availability, root architecture becomes an even more critical feature in plant survival and productivity."
Muday grew up in a gardening family in Eastern North Carolina.
"My mother, Ruth Kressin, and her mother were both avid gardeners as was my paternal grandmother, so I grew up appreciating gardening," Muday said.
Muday studied biochemistry and genetics and was excited to delve in to the study of plant hormones, which was just becoming possible at that time.
Last year, Muday and her students began growing tomatoes in her colleague Pete Weigl's garden, but they quickly ran out of room for the number of plants they would need. Muday contacted Kim MacPherson, who was acting as farm manager at The Children's Home, and they arranged a produce-for-plant space arrangement. Figuring that the demand for Neverripe tomatoes would be pretty slim, the Wake Forest researchers added some more conventional vegetables to their patch. These were contributed to the farmers market at The Children's Home in exchange for their use of garden space.
The goal of much of the gardening here is producing seed to use in lab experiments. Each experiment in the lab will involve 50 to 100 seeds germinated and grown in petri dishes and agar solutions, where the habits of the roots can be studied. An experiment might involve exposing plants to five or six gradations of ethylene, each requiring its quota of seed. With four students conducting studies, each with his or her own thesis, one can see how the demand for seed would be great.
There is a Zen quality to much of the work involved. Muday observed that understanding what is broken in these mutations leads to understanding how things work. She said that the research has already produced some conclusive answers, but "the nature of the process is that as soon as you answer one small question, you get many more questions." Questions that may one day lead to an ability to grow crops in environments we had not previously imagined.
■ If you have a gardening question or story idea, write to David Bare in care of Features, Winston-Salem Journal, P.O. Box 3159, Winston-Salem, NC 27101-3159, or send e-mail to his attention to gardening@wsjournal.com.
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