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Science

Shipwreck!

by Jodi Wheeler-Toppen

Two boats race down the Connecticut River. Suddenly, the current shifts and drives one into the other. The smaller boat smashes against the side of the larger and its capsized remains float downstream. Is it a disaster? Not at all. This shipwreck is part of the normal life of the eel grass plant.

Most flowers are pollinated by insects or other animals, but a few plants have found unusual ways to do it themselves. Eel grass (Vallisneria americana), sometimes called tape grass, uses tiny shipwrecks to transfer pollen from the male flowers to the female flowers. The plant is common in rivers and streams throughout the eastern United States. For most of the year, it grows under water. But in the spring, it releases boat-like flowers that rise to the surface for pollination.

Eel grass has separate male plants and female plants. The female plants produce tiny female flowers that are each attached to thin stems. The stems grow quickly until the flowers reach the surface, but they stay tied to their mother plant.

At the same time, the male plants grow a pocket that is full of tiny male flower-boats. Each boat is about the size of the tip of a pencil. The pocket opens and the flowers float slowly up to the surface. These flowers are not attached to a stem, so they are free to sail downstream. Two petals fold down to guide the ship like rudders, and one sticks up in the air like a sail. The stamens, which hold the pollen, stand straight in the middle like a mast.

The male boats are surprisingly stable. Even when they are swept along in the rushing current, they rarely capsize. That is, until they encounter a female. The female boat rests on the surface of the water. Whenever a small wave pulls the boat forward, the stem tugs it back toward the mother plant. This creates a dimple in the water. The dimple works like a waterfall, sucking nearby male boats into the female flower. In the collision, the male flower dumps its pollen load onto the female
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The remains of the capsized male boat are swept downstream until they are eaten by a fish or just washed away. The stem holding the female boat coils and gently pulls the pollinated flower back to the mother plant. The seeds spend the winter protected in a pod that looks like a miniature green bean. In the spring, a new eel grass plant will grow, and another fleet of flower-boats will be ready to set sail.

The End

Bibliography:

Attenborough, D. (1995). The Private Life of Plants. Princeton, New Jersey: Princeton University Press.

Morris, M. and M. Bastiaan. (1984). The Sex Life of Flowers. New York: Facts on File Publications.

Radford, A., H. Ahles, and C. Bell. (1968). Manual of the Vascular Flora of the Carolinas. Chapel Hill: University of North Carolina Press.

Sculthorpe, C. D. (1985). The Biology of Aquatic Vascular Plants. Konigstein, West Germany: Koeltz Scientific Books.

Wylie, R. B. (1917). The Pollination of Vallisneria spiralis. Botanical Gazette, 63: 135- 145.

Jodi Lyn Wheeler-Toppen is a former high school biology teacher. She is now writing and working on her Ph.D. in science education.

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