Chapter 28, Problem 4DAA

TCE Uptake by Transgenic Plants Plants used for phytoremediation take up organic pollutants, then transport the chemicals to plant tissues, where they are stored or broken down. Researchers are now designing transgenic plants with enhanced ability to take up or break down toxins. In 2007, Sharon Doty and her colleagues published the results of their efforts to design plants for phytoremediation of soil and air containing organic solvents. The researchers used Agrobacterium tumefaciens (Section 15.7) to deliver a mammalian gene into poplar plants. The gene encodes cytochrome P450, an enzyme involved in the breakdown of a range of organic molecules, including solvents such as TCE. FIGURE 28.16 shows data from one test on the resulting transgenic plants.

FIGURE 28.16 TCE uptake from air by transgenic poplar plants. Individual potted plants were kept in separate seated containers with an initial level of TCE (trichloroethylene) around 15,000 micrograms per cubic meter of air. Samples of the air in the containers were taken daily and measured for TCE content. Controls included a tree transgenic for a Ti plasmid with no cytochrome P450 in it (vector control), and a bare-root transgenic tree (one that was not planted in soil.

4. Assuming no other experiments were done, what two explanations are there for the results of this experiment? What other control might the researchers have used?