Macrocystis
Encyclopedia
Macrocystis is a genus of kelp
Kelp
Kelps are large seaweeds belonging to the brown algae in the order Laminariales. There are about 30 different genera....

 (algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

). This genus contains the largest of all the phaeophyceae or brown algae
Brown algae
The Phaeophyceae or brown algae , is a large group of mostly marine multicellular algae, including many seaweeds of colder Northern Hemisphere waters. They play an important role in marine environments, both as food and for the habitats they form...

. Macrocystis has pneumatocyst
Pneumatocyst
In phycology, a pneumatocyst is a large float containing gas found in brown algae. An organism may have more than one. They provide buoyancy to lift the blades toward the surface, allowing them to receive more sunlight for photosynthesis....

s at the base of its blade
Blade
A blade is that portion of a tool, weapon, or machine with a cutting edge and/or a pointed tip that is designed to cut and/or puncture, stab, slash, chop, slice, thrust, or scrape animate or inanimate surfaces or materials...

s. Sporophyte
Sporophyte
All land plants, and some algae, have life cycles in which a haploid gametophyte generation alternates with a diploid sporophyte, the generation of a plant or algae that has a double set of chromosomes. A multicellular sporophyte generation or phase is present in the life cycle of all land plants...

s are perennial, and individual stipes may persist for many years. Common along the coast of the eastern Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

, from central California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

 to Baja California
Baja California
Baja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...

 and north to southeast Alaska (Sitka).

One species, Macrocystis pyrifera
Macrocystis pyrifera
Macrocystis pyrifera, commonly known as Giant kelp or Giant bladder kelp, is a species of kelp , and one of four species in the genus Macrocystis...

, under this genus, has the fastest linear growth of any organism on earth. They can grow two hundred feet long at a rate of two feet a day.

Description

Macrocystis is a genus of kelp, some species of which are so huge that the plants may grow to up to 60 m (200 ft). The stipes arise from a holdfast
Holdfast
A holdfast is a root-like structure that anchors aquatic sessile organisms, such as seaweed, other sessile algae, stalked crinoids, benthic cnidarians, and sponges, to the substrate. ...

 and branch three or four times from near the base. Blades develop at irregular intervals along the stipe. M. pyrifera grows to over 45 m (150 ft) long.

The stipes are unbranched and each blade has a gas bladder at its base.

Life cycle

The sporophyte
Sporophyte
All land plants, and some algae, have life cycles in which a haploid gametophyte generation alternates with a diploid sporophyte, the generation of a plant or algae that has a double set of chromosomes. A multicellular sporophyte generation or phase is present in the life cycle of all land plants...

 has many sporangia located in its blades, which, through meiosis
Meiosis
Meiosis is a special type of cell division necessary for sexual reproduction. The cells produced by meiosis are gametes or spores. The animals' gametes are called sperm and egg cells....

, 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 than 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
Zygote
A zygote , or zygocyte, is the initial cell formed when two gamete cells are joined by means of sexual reproduction. In multicellular organisms, it is the earliest developmental stage of the embryo...

, 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.

Species

There are four species of macrocystis.
  • Macrocystis angustifolia Bory de Saint-Vincent

  • Macrocystis integrifolia Bory de Saint-Vincent, Great kelp

  • Macrocystis laevis C.H.Hay;

  • Macrocystis pyrifera (L.) C.Ag, Giant kelp, Giant bladder kelp; and M. pyrifera var. humboldtii Bomplan.

Distribution

  • Macrocystis pyrifera, known as giant kelp, is found in North America
    North America
    North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

     (Alaska
    Alaska
    Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...

     to California
    California
    California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

    ), South America
    South America
    South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

    , South Africa
    South Africa
    The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

    , New Zealand
    New Zealand
    New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

    , and southern Australia
    Australia
    Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

    . It can grow over 45 metres long and can do so in one growing season, making it the organism with the world's fastest linear growth.
  • Macrocystis integrifolia, a smaller, intertidal species, is found on the Pacific coast of America
    North America
    North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

     (British Columbia
    British Columbia
    British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...

     to California
    California
    California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

    ) and South America.

  • Macrocystis integrifolia is much smaller, the sporangial thalli growing only to 6 m long; it is found on intertidal rocks or shallow subtidal rocks.

  • Macrocystis angustifolia Bory is found in Australia.

Further reference

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

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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