Stomata respond to light, pathogens, changes in humidity and, most important for his study, drought conditions. McAdam will investigate if stomatal function varies across plants, and whether this variation might determine where species grow and how well they survive stress.
“Closing stomata are critical for drought tolerance,” he says. “If stomata don’t close, the plant will dry out very fast and die. We don’t know what signals drive stomata closure during drought: How does the plant know it is experiencing a drought and that the stomata need to shut?”
McAdam will try to answer that question and others using ferns and lycophytes, ancient groups of plants that have comparatively simple stomatal behavior, and in which variation in stomatal function is likely to have a large impact on plant growth and survival. “The idea is that these pores are so important for photosynthesis and survival during stressful conditions, any variation in the way the stomata might work would have huge implications for a plant’s ecology or the way it tolerates drought and its success as a species,” he explains. “So modifying stomatal function even slightly might have big implications for the evolution of new groups of plants or survival in interesting or stressful environments.”
Some ferns for the study will come from the collection of plants McAdam has amassed in the Purdue greenhouses and others from southern Indiana. He also will travel to Mexico to collect a lycophyte from the genus Selaginella that grows in deep ravines there. He has seen only a leaf of this elusive plant and hopes to bring it back to grow at Purdue.