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SDSU research: Weeds grow bigger among corn

The axiom, "growing like a weed," takes on new meaning in light of changes in gene expression that occur when weeds interact with the crops they infest, according to Plant Scientist Sharon Clay.

Using sophisticated genetic-mapping techniques, the South Dakota State University professor and her research team are documenting how corn and weeds influence one another.

"Weeds grow like weeds when they grow with corn," Clay said. "They grow bigger and taller in corn than by themselves. And inversely, "corn grows less among weeds."

To figure out how corn and weeds affect each other's gene response, Clay and a team of two research associates and a soils expert planted plots of velvetleaf alone, corn with velvetleaf and corn kept weed-free.

The researchers saw an entirely different response when velvetleaf was grown by itself versus among corn plants. The velvetleaf alone was shorter and stouter. In addition, specific genes that influenced photosynthesis and other important plant responses differed in expression.

Another study compared the corn's growth and yield in response to weeds, lack of nitrogen or shade. In all cases, the researchers found that genes were different compared to non-stressed plants.

Traditionally, weeds have been thought to reduce crop growth and yield due to competition for water, nutrients and light. This study, however, indicates that weed-crop interactions are much more complex than researchers have thought.