"Mouse-ear cress," Arabidopsis thaliana

EDITOR’S NOTE: The Georgetown Times features John Nelson’s Mystery Plant series each Wednesday. You can find the answer to today’s mystery plant next Wednesday.

The answer to last week’s Mystery Plant is: ”Coral catbrier”, Smilax walteri

It is a tiny little plant with a great big name. This in one that has found its way out of Europe and Asia, far into the New World and Australia, as a common weed, and now thrives on roadsides, open paths, and in vacant lots. Not only that, it has found its way, with the help of modern plant biologists, deep into scientific labs all around the world. In fact, although it is common out of doors, you might be more likely to see it in a scientific setting indoors, as it is a very unassuming little thing, not at all conspicuous, and not very competitive when lined up against our local wildflowers.

This is a plant in the mustard family, and is therefore related to cabbage, horseradish, Brussels-sprouts, wasabi, and turnip, among others. It is an annual, and it has an extremely quick life cycle, able to sprout from seeds and grow, soon blooming and setting its own seeds (lots of them), then drying up and disappearing, all in a few short weeks. Its tiny leaves are mostly basal, in what we call a rosette, and the slender stems may reach up to a foot tall on large plants, although are usually shorter than that.

The flowers are typical of the mustard family, with flowers on tiny stalks in rows up and down the stem. Each flower bears four teeny white petals. The petals, at right angles to each other, form something of a cross…and this too is characteristic of the mustards, and gives us the old-timey scientific name for the family, which is “Cruciferae,” meaning cross-bearing. Botanists these days, though, are encouraged to use the more modern family name, “Brassicaceae”.

The short life cycle is one thing that has made this plant very interesting to botanists. It is very easy to grow in the lab, and actually represents a model organism for scientific research. Each of its cells contains ten chromosomes, a relatively low number for most plants, and these are easy to study. Beyond that, the thousands of genes packed onto the chromosomes are themselves easy to study and manipulate. The image provided here shows an herbarium specimen, pressed and dried, of our little Mystery Plant. Although it is one of the most common and inconspicuous weeds in the Southeast, our little friend has become an indispensable part of thousands of sophisticated genetic and molecular studies on plants. These studies, beyond providing knowledge on the complicated interactions of genetic and environmental expression, may hold keys, in the future, to the development of larger crop plants, potentially capable of producing larger fruits and vegetables. You wouldn’t think that such a humble little weed could be so important.

John Nelson is the retired curator of the A. C. Moore Herbarium at the University of South Carolina, in the Department of Biological Sciences, Columbia SC 29208. As a public service, the Herbarium offers free plant identifications. For more information, visit www.herbarium.org or call 803-777-8196, or email nelson@sc.edu.