Scanning Electron Microscope Images of Desert Laboratory Winter Annual Seeds
Half of the plant species found at the Desert Laboratory in Tucson Arizona are desert annuals. Desert annuals spend most of their lives, sometimes years, as seeds unseen at or below the soil surface. Hence half of the species in this desert community are easily overlooked much of the time. Despite their diminute scale, desert winter annual seeds possess amazingly complex surface features many of which have unknown evolutionary origin and ecological function.
Using a scanning electron microscope we imaged seeds ranging in length from one centimeter to less than one millimeter to reveal the hidden complexities of these unseen phantoms of the desert. All of these seeds are from winter annuals found in nature at the Desert Laboratory at Tumamoc Hill, Tucson Arizona. We've been looking at these seeds for years, but many ecologically relevant traits are not readily apparent to the naked eye. For instance, we knew that the seeds in the Brassicaceae family have a thin layer of mucilage that helps them adhere to surfaces when wet, but we hadn't seen the geometric surface patterns unique to each species. Seeds of Castilleja excerta are surrounded by a “bird cage” formed by programmed death of seed coat cell walls and cell layers that helps them disperse in the wind. We invite you to browse the images and discover more intricate complexities of form for yourself.
This project was conceived by Judith Becerra, Ben Wilder and Larry Venable and the seeds were imaged by Nick Roalofs under the guidance of Larry Venable and Ursula Basinger using a S-3400 VP-SEM, Variable Pressure Scanning Electron Microscope at the Imaging Cores - Materials Imaging and Characterization Facility on the University of Arizona campus with support from the Desert Laboratory at Tumamoc Hill and the National Science Foundation. For permission to use these original images, please contact Larry Venable at firstname.lastname@example.org.