Herbicide Tolerant Plants - The presence of weeds in a crop field reduces the yield. Weed killers or herbicides are not very selective and their current use relies on differential uptake between the weed and the crop plant or on application of the herbicide before planting a field, altering the food content of plants. With the ability to introduce DNA into plants, researchers are trying to create herbicide-tolerant crops by three strategies.

1. Increasing the level of the target enzyme for a particular herbicide.

2. Expressing a mutant enzyme that is not affected by the compound.

The third strategy for creating herbicide tolerant plants is by transgenic expression of enzymes that convert the herbicide to a form that is not toxic to the plant. Some plants have developed their own detoxifying system for certain herbicides. But these activities in plants are encoded by a complex set of genes that has not yet fully characterized.