Sight Lines: Life in Detail

Perspectives: Research and Creative Activities at SIUC, Fall 2007

:: sight lines ::

Life in Detail

The evolution of early land plants is the research focus of Ryan McMillen, who works in the laboratory of plant biologist Karen Renzaglia on a National Science Foundation project called Assembling the Tree of Life. The lab traces evolutionary relationships in part by using electron microscope images to study minuscule plant structures.

Scientists knew that, in seed-bearing plants, the length of tiny pores called stomata correlates to the size of the plant's genome (its total DNA package). But no one knew if the same was true for seedless plants such as ferns and mosses, which evolved earlier. With funding from an SIUC Undergraduate Research/Creative Activity Award, McMillen made electron micrographs of stomata from various species and compared measurements with genome size. He found a direct correlation. This means that stomatal length in fossilized seedless plants could indicate relative genome sizes among the earliest land plants—a key to establishing evolutionary events and relationships.

McMillen presented his findings at the Plant Biology and Botany 2007 Joint Congress in Chicago, and one of his electron micrographs (shown here) won third place in a student plant-imaging competition sponsored by the Botanical Society of America. The photo, published in the American Journal of Botany in September 2006, is of a stoma in a horsetail fern native to Illinois.

—by Marilyn Davis