Spiderworts

It's spiderwort time, with narrow, grasslike leaves zigzagging up the stem, topped by cascades of pink, blue, violet or white flowers, Each blooms for only a day, as the next day's three-petaled flowers get ready to burst open early in the morning, fading in early afternoon.

There are 30 species in the genus Tradescantia, from North America, named for John Tradescant, gardener to Charles I of England. They hybridize readily, and most spiderworts in horticulture are hybrids. Along our roadsides, Tradescantia ohiensis, Ohio spiderwort is the common species.

Look very closely at the flowers and notice that the filaments of the stamens have hairs, up to ½ in. long. Look even closer, and be amazed.

Stamen hairs consist of an elongated chain of twenty to thirty-five cells -- cells so large that they can actually be seen by the naked eye (if you're young), and easily seen with a 10x or 20x magnifying glass.

This interesting garden perennial has a number of laboratory and educational uses. The beginning botany student may well have used the root tips or pollen grains to study chromosome structures. Compared with other plants, spiderworts have a relatively low number of large chromosomes, making them useful in biological test systems.

The spiderwort was chosen as a passenger of the first United States biosatellite sent up in the late 1960s to explore effects of weightlessness on living organisms. As early as 1950, spiderworts were used to indicate the effects of radiation on living organisms. In certain clones of spiderwort, the normally blue stamen hair cells turn pink when exposed to chemical or radiological mutagens.

How does the spiderwort's built-in Geiger counter work? The spiderwort clones possess a dominant gene for blue and a recessive gene for pink. On exposure to even minute levels of radiation or chemical mutagens, a mutation may occur, causing the loss of the dominant blue gene which shows up as a pink mutated cell. Pink cells appear eight to 18 days after exposure to the mutagen. The same kind of somatic (body cell) mutation in humans from short-term exposure to low levels of radiation, might only be detected after several decades.

For the gardener, the best thing about spiderworts is that they thrive on neglect which even a botanist can't kill.