Tiny Breathing Plant Mouths

When Keiko Torii gazed through the microscope at a mutant Arabidopsis thaliana leaf covered in specialized cells called meristemoids, she saw more than a beautiful anatomic anomaly–she saw a new way to probe a fundamental system in developmental biology.

Meristemoids are stem-cell-like precursors that give rise to a pair of guard cells, which form stomata–tiny pores on the skin of almost all land plants that are crucial for the exchange of water vapor and gas during photosynthesis. Close study of meristemoids has largely eluded scientists because the cells, by nature, are transient and few and far between.

“When I looked at this,” Torii says, pointing to a poster-size image of the mutant leaf with a tightly packed honeycomb of DayGlo blue meristemoids hanging on her office wall at the University of Washington, “I thought maybe this could be an economical tool to study what makes a meristemoid a meristemoid.”