The Large and the Small of It
In past nature experiences, I remember seeing still ponds that looked for all the world like flat concrete slabs, painted bright green. At one time I thought that the green color was due to some type of algal growth on the surface of the pond. Since then, I've learned that the green color was caused by multitudes of a very tiny flowering plant known as Wolffia. These very little gems have the distinction of being the smallest flowering plant in the world (see thumbnail picture at right). As you can see, they are small enough to span only two ridges of a fingerprint! This makes them less than 1 millimeter in size, and yet even a plant this tiny is capable of blooming.
A Titan for a cousin?
Even more intriguing is that Wolffia has been classified as a member of the Araceae, or aroid family. This is the same family in which Amorphophallus titanum, the Titan Arum, is found. The family resemblance is very elusive due to the extremely small size of Wolffia plants, but genetic studies have verified that there is, indeed, a familial relationship.
Wolffia is a genus in the Lemnaceae, or Duckweeds. The photo at left shows two members of the family, Wolffia globosa and Spirodela polyrhiza. The genera of the Lemnaceae are closely allied to the genus Pistia, or water lettuce, which is a plant large enough for the typical aroid morphology to be visible in the inflorescences. A study of the different genera of Duckweed shows that the largest ones do bear some resemblance to a very small Pistia plant. Then you notice the smaller and smaller species, where the plants are reduced to just two leaves and a root or two, then to one "leaf" and no root, then to something more reminiscent of yeast bodies than of a flowering plant. Wolffia is the smallest of the small in the Lemnaceae, and yet it still blooms and produces fruit and seed!
A Bouquet on the Head of a Pin!
I can't overemphasize how tiny these little guys are, as a dozen Wolffia blooms could be arranged tastefully on the head of a pin. While they are flowering plants capable of producing seeds, Wolffia reproduces most commonly by vegetative means. A mature plant will produce a bud which will grow into an individual plant and separate off from the parent. Their capacity for vegetative reproduction is incredible, as the Indian species Wolffia microscopica can produce a smaller daughter plant every 30 to 36 hours. At this rate of reproduction, one plant could give rise to about 1 nonillion (a one followed by 30 zeros) in a period of only 4 months. Fortunately, these plants are edible and are similar to soybeans in their protein content. In fact, Wolffia is eaten by people in Thailand. It is known there as "water-eggs" or khai-nam.
A Large Future for such a Small Plant
Wolffia have the potential to help solve some of the world's most pressing problems, from bioremediation of polluted waters to serving as a food source for humans and animals, to even providing biofuel to lessen our dependence on oil. Such amazing possibilities for such a diminutive plant, and incurably cute, too!