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Laminaria Blade

Members of the genus Laminaria are often better known as kelps, large brown seaweeds belonging to the order Laminariales. Superficially kelps appear similar to plants: they possess leaf-like structures called fronds, long, narrow stipes similar in shape to stems, and branching root-like structures called holdfasts.

Laminaria Blade

Despite their resemblance in form, however, kelps are algae and their structures differ in several important ways from those of plants. Most notably, the stipes of kelps are flexible and rubbery so they can withstand the turbulence created by waves and do not transport nutrients or water to the fronds. Likewise, the holdfasts of the algae do not provide mineral or water uptake, but function only in anchoring kelps to the sea floor or to other surfaces. Kelps do not produce flowers or seeds and reproduce through alternating asexual and sexual generations.

Several species of Laminaria are harvested for a variety of uses, including human consumption, iodine extraction, crop fertilization, and medical applications. The kelps usually range from about three feet to nearly ten feet long and range in color from light to dark brown. They are most plentiful along the coasts of the Pacific Ocean and in the north Atlantic around the British Isles. The stipes of Laminaria may survive for a number of years, though the blades that comprise their fronds perish on an annual basis. Some of the most familiar species include L. digitata, commonly called oarweed, and L. saccharina, known as sugar kelp because of its sweet taste.

Contributing Authors

Nathan S. Claxton, Shannon H. Neaves, and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.