In response to the presence of water or the lack of water, or in response to light or other stimuli, guard cells control the opening and closing of pores on leaves that help moderate the amount of water and carbon dioxide in the plant. The guard cells balance the plant's priorities. Among many potential practical applications are uses for farmers. For example, if biologists can engineer crop plants, farmers might be able to better control how the plants respond to the weather during the growing season. Also, if the opening and closing of pores on plant leaves can be controlled, farmers might be able to alter the percentage of water in their crop when they take it to market.
Water content plays an important role in determining the quality and value of the crop.
Ironically, Assmann gravitated to plant biology because of her love of animals. That's not something that appealed to me. As a professor, her enthusiasm for her work and her willingness to collaborate have served both her and the department well. When that happens, it's incredibly rewarding.