WORLD'S SMALLEST PLANT

WOLFFIA

A recent article by J. Travis in Science News Vol. 155 (April 17, 1999) discusses a remarkable new species of sulfur bacteria from the greenish ooze of ocean sediment off the coast of Namibia in southwestern Africa. Sulfur bacteria oxidize sulfur compounds to produce their energy-rich ATP molecules. The spherical bacteria have diameters ranging from 0.1 to 0.75 mm, definitely within the size range of some species of Wolffia. In fact, some multicellular orchid seeds are less than 0.2 mm in diameter, smaller than this bacterium. Considering that a unaided human eye with 20-20 vision has resolving power of 0.1 mm, this bacterium is visible to the naked eye. Because of their size and light-reflecting properties, the bacteria appear to be roughly the size of a printed period or the size of an average grain of table salt (NaCl). The bacteria were discovered in sediment samples by Heide Schulz of the Max Planck Institute for Marine Microbiology in Bremen, Germany (see the April 16, 1999 issue of Science). The new species is named Thiomargarita namibiensis, or sulfur pearl of Namibia. When light shines on the bacterial cells, they glisten white from light reflecting off sulfur inside them (see the image above). But who would ever believe that a multicellular flowering plant could be as small as one prokaryotic bacterial cell. This is certainly the case with Wolffia globosa, especially if you consider the size of a single daughter plant that has broken away from the parent plant by budding (see the images above). And although it is the ultimate in reduction of a flowering plant, it actually has minute guard cells and stomata on its upper (dorsal) surface. Any way you look at these amazing records; a giant bacterial cell or a microscopic flowering plant, they are truly wonders of the world.