While photographing small Acmaeodera beetles on flowers of Tradescantia ohioensis at Packsaddle Wildlife Management Area, I thought I should take a photo of the flower itself. Flowers of Tradescantia species, or spiderworts, are notable for their bright yellow anthers and filaments with numerous hairs. Each of the (usually) six stamens possesses around 70-100 hairs, which in turn are composed of a chain of about 20 large, single cells that are purple in color and contain a large, water-filled central vacuole. The cells can be seen easily with low magnification – click on the photo to see the larger version, with the individual cells that make up each hair clearly visible. I haven’t been able to ascertain the function of these hairs for the plant, but their usefulness in observing division in plant cells (the flowing cytoplasm and nucleus can be seen easily) and their sensitivity to radiation and chemical mutagens have been recognized for many years. The hairs turn pink when exposed to radiation, allowing them to be used as a sort of ‘natural’ Geiger counter.
Update: While writing this post, I sent an email to George Yatskeivych, botanist at the Missouri Botanical Garden and author of Steyermark’s Flora of Missouri (1999, 2006), asking if he knew the function of the filamental hairs. After reading his response (below), I don’t feel quite so bad for not being able to determine the answer myself:
I don’t know that I have ever heard anyone express a particular use for the hairs on the filaments of Tradescantia species. Sometimes, hairy filaments help to trap pollen from visiting insects in proximity to the stigma or act as nectar guides, but I do not think that anyone has determined such “uses” in Tradescantia. There may not be a selective advantage to hairy filaments in the genus.
If any botanist happens to read this post and has some insight about this, a comment would be most appreciated.
Yatskievych, G. 1999. Steyermark’s Flora of Missouri, Volume 1. Missouri Department of Conservation, Jefferson City, 991 pp.
Yatskievych, G. 2006. Steyermark’s Flora of Missouri, Volume 2. The Missouri Botanical Garden Press, St. Louis, 1181 pp.
Copyright © Ted C. MacRae 2009