Macrocystis is a genus of kelp (algae). This genus contains the largest of all the Phaeophyceae or brown algae. Macrocystis has pneumatocysts at the base of its blades. Sporophytes are perennial, and individual stipes may persist for many years. Common along the coast of the eastern Pacific Ocean, from central California to Baja California.

A species found under this genus called Macrocystis pyrifera are perhaps the largest, fastest growing organism on the planet.^[1] They can grow up to two hundred or so feet long, up to two feet more a day.

Description

Macrocystis is a genus of kelp, some species of which are so huge that the plants may grow to up to 60m (200ft).^[2]The stipes arise from a holdfast and branch three or four times from near the base. Blades develop at irregular intervals along the stipe.^[3][4] M. pyrifera grows to over 45m (150ft) long.^[4]http://www.mbari.org/staff/conn/botany/browns/james/default.htm^[5]

The stipes are unbranched and each has a gas bladder at its base.^[6]

Life Cycle

The sporophyte has many sporangia located in its blades, which, through meiosis, releases haploid spores, which will grow into female and male gametophytes. These gametophytes grow mitotically, and produce gametes, sperm and eggs. The gametophytes are microscopic. The female has larger and fewer cells then the male. The male releases its sperm, which find their way to the female, following a pheremone released by the female, there it fertilizes the egg, to form the zygote, which, through mitosis, begins growth.

Growth

Juvenile giant kelp grow directly on the parent female gametophyte, extending one or two primary blades, and beginning a rudimentary holdfast, which will eventually cover the gametophyte completely. Growth occurs with lengthening of the stipe, and splitting of the blades. This occurs by means of small tears where the blade meets the stipe, which splits the stipe into two. Pneumatocysts grow after the first few blade splittings.

Ecology

Grows forming extensive beds, large "floating canopies", on a rocky substrate.^[4]

Species

There are four species of Macrocystis in the world. Macrocystis angustifolia Bory de Saint-Vincent; M. intergrifolia Bory de Saint-Vincent; M. laevis C.H.Hay; M. pyrifera (L.) C.Ag; and M. pyrifera var. humboldtii Bomplan.http://www.algaebase.org/generadetail.lasso?genus_id=35715&-session=abv3:51909EC307dcf25DFApmi3530315

Distribution

Macrocystis pyrifera, giant kelp, is to be found in North America (Alaska to California), South America, South Africa, New Zealand, and southern Australia. http://www.algaebase.org/search/species/detail/?species_id=4427 Macrocystis integrifolia, a smaller, intertidal species, is found on the Pacific coast of America (British Columbia to California) and South America. ^[4] M. pyrifera grows to over 45 m long ^[4] and can do so in one growing season, making it the organism with the fastest linear growth. M. integrifolia is much smaller, the sporangial thalli growing only to 6 m long; it is found on intertidal rocks or shallow subtidal rocks.^[4]http://www.algaebase.org/search/species/detail/?species_id=4882&sk=0&from=results

Mycrocystis angustifolia Bory is found in Australia.^[7]http://www.algaebase.org/search/species/detail/?species_id=3464&sk=0&from=results

References

1. ↑ BrnAlgae
2. ↑ Hoek, C. van den, Mann, D.G. and Jahns, H.M. 1995. Algae An Introduction to Phycology. Cambridge University Press, Cambridge. ISBN 0 521 30419 9
3. ↑ Mondragon, J. and Mondragon, J. 2003. Seaweeds of the Pacific Coast. Sea Challengers, Monterey, California. ISBN 0-930118-29-4
4. ↑ ^{a b c d e f} Abbott, I.A. and Hollenberg, G.J. 1976 Marine Algae of California. Stanford University Press, California. ISBN 0-8047-0867-3
5. ↑
6. ↑ Kain, J.M. (Jones) 1991 Culivation of attached seaweeds. in: Guiry,M.D. and Blunden, G. 1991 Seaweed Resources in Europe: Uses and Potential. John Wiley and Sons
7. ↑ Huisman, J.M. 2000. Marine Plants of Australia. University of Western Australia Press. ISBN 1 876268 33 6

External links

• http://www.mbari.org/staff/conn/botany/browns/james/default.htm Macrocystis pyrifa
• http://ucjeps.berkeley.edu/guide/brown61.html Macrocystis integrifolia

Further reference

Lopez, James. "Macrocystis pyrifera." Monterey Bay Aquarium Research Institute. 2001. Monterey Bay Aquarium Research Institute. 10 Jan 2007 fr:Macrocystis