How to use this resource
This scenario accompanies the online lesson, "Transpiration - Water Movement Through Plants", and is designed to allow you to apply the concepts learned in that lesson to a real-life problem.
Meet Brandon, a farmer in south-central Nebraska. Brandon raises daughters for fun and corn for profit.
Brandon hears about a new type of genetically engineered corn that is being developed to be drought resistant. Brandon is an expert on growing corn in water limiting conditions.
Brandon has learned about the crop genetic engineering process and knows that scientists can add a single gene to a plant like corn and change a single trait in the plant. Biotechnology companies are doing this to develop new types of corn for farmers to grow. Companies, however, will not reveal all the details of their new projects until they are finished testing them. Learn about the plant genetic engineering processes in Overview of Plant Genetic Engineering: Overview and Objectives.
Brandon wonders if adding a single gene to corn can affect a trait like drought resistance. Brandon believes that his success in farming depends on his ability to think ahead about the practical value of different options. Therefore, he contacts his teacher friends in the Agronomy and Horticulture department. He wants to know what they can tell him about this drought resistance trait in corn.
One teacher and researcher in Agronomy and Horticulture is Dr. Jim Specht. Jim is an expert in soybeans and how they use their genes to grow under water limited conditions. He has a pretty good idea what the biotechnology company is doing to produce their drought resistant genetically engineered plants.
The gene the biotechnology company has inserted into corn is probably a version of the DREB1A gene. The DREB1A activates the expression of other genes that govern the plant’s response to cellular dehydration and when these genes are turned on, they produce proteins that allows the plant to better cope with water stress. Jim’s hypothesis is that this work involved some very good molecular genetics research. However, Jim believes that in growing conditions in places like Nebraska, the DREB gene would ultimately influence the function of the cells pictured below.
The biotechnology company shows pictures of plants with the transgene (genetically engineered plants). They do not roll their leaves under the same field conditions that cause the non genetically engineered plants to roll their leaves. Leaf rolling is a common response of plants such as corn to the water conditions.
Jim’s concern with the genetic engineering approach is that by making the DREB1A gene more easily turned on when stress occurs, this transgene could have a drag on the yield process because the coping mechanisms are also turned on earlier. In other words, the transgenic plant is now more “sensitive” in its response to water stress. The key question then is how soon does the plant begin “saving” water.
Jim Specht has read the research reports that indicate that plants that save water also do not yield as well as those plants that use all of the seasonally available water. He has also observed this with in own studies in soybean. He notes that yield is not improved if stomates close sooner and longer, since corn then cannot obtain the carbon dioxide it needs for photosynthesis to fix carbon it needs for vegetative growth and ultimately for grain. . Simply put, the trend in grain crops is that more transpiration – more seed yield (and unfortunately, vice-versa).
Development of this lesson was supported in part by the Cooperative State Research, Education, & Extension Service, U.S. Dept of Agriculture under Agreement Number PX2003-06237 administered by Cornell University, Virginia Tech and the American Distance Education Consortium (ADEC) and in part by the New Mexico and Nebraska Agricultural Experiment Stations. Any opinions , findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.