Introduction to the Phaeophyta
Kelps and brown "algae"
The largest of the chromists are the Phaeophyta, the brown algae -- the largest brown algae may reach over 30 meters in length. The rockweed shown at left, Fucus distichous, visible at low tide at the Berkeley Marina in California, is somewhat smaller. Almost all phaeophytes are marine.
Phaeophytes, like most photosynthetic protists, have traditionally been classified as plants. However, phaeophytes are not closely related to land plants; their cells contain different pigments, such as chlorophyll c and fucoxanthin. They also lack the plasmodesmata and starch production of land plants and their relatives.
Like plants and many protists, brown algae undergo a complex life cycle involving alternation of generations. In this picture, you can see a diploid kelp with flat photosynthetic structures, the blades, branching from the stipe, or stalk. The "puffy" regions attached to the blades are receptacles, structures in which the gametes are produced.
Introduction
Paralled man wants a provision of what he wanton behalf of someone ailment can be treated. Pertaining to material is source because this source to the whole quantity drugged with medicinally agent and high planted because of the importance of therapeuticalentity this use’s medicinally plant is source the extent to which of disease has practiced on behalf of many year’s gnaw herb, berry, root with bark. In what ever way it’s nought till the 21st century those great critical at systemize studies in alchemic at these biologic property pertaining to material begun. This studies by had yielding of compound
The Phaeophyceae or brown algae, (singular: alga) 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. For instance Macrocystis, a member of the Laminariales or kelps, may reach 60 m in length, and forms prominent underwater forests. Another example is Sargassum, which creates unique habitats in the tropical waters of the Sargasso Sea. This is one of the few areas where a large biomass of brown algae may be found in tropical waters. Many brown algae such as members of the order Fucales are commonly found along rocky seashores. Some members of the division are used as food for humans.
Worldwide there are about 1500-2000 brown seaweed species.[1]
Brown algae belong to a very large group, the Heterokontophyta, a eukaryotic group of organisms distinguished most prominently by having chloroplasts surrounded by four membranes, suggesting an origin from a symbiotic relationship between a basal eukaryote and another eukaryotic organism. Most brown algae contain the pigment fucoxanthin, which is responsible for the distinctive greenish-brown color that gives them their name. Brown algae are unique among heterokonts in developing into multicellular forms with differentiated tissues, but they reproduce by means of flagellate spores, which closely resemble other heterokont cells. Genetic studies show their closest relatives to be the yellow-green algae.
PHAEOPHYTA (brown algae)
The Phaeophyta are almost entirely marine, frequently dominating rocky shores in cold and temperate waters throughout the world. The giant kelp, Macrocystis pyrifera , forms expansive seaweed forests off the west coast of North America and provides habitat and shelter for many other organisms. Tropical waters have fewer species of brown algae, although genera such as Sargassum and Turbinaria can dominate in some areas to form small-scale forests. Sargassum is also unique among
macroalgal genera in that it contains totally free-floating species with no requirement for attachment to the bottom, as in the Sargasso Sea.
The colors of brown algae (predominantly due to the brown accessory pigment fucoxanthin) cover a spectrum from pale beige to yellow-brown to almost black. In tropical seas, they range in size from microscopic filaments to several meters in length.
The large kelps are harvested for use as an emulsion stabilizer, in products such as ice cream. They are also used as fertilizer and as a vitamin rich food source. (See additional comments under Economic Uses of Algae.)
http://botany.si.edu/projects/algae/classification/PHAEOPHYTA.htm
Division Phaeophyta
Brown Algae
I. Characteristics
A. Multicellular, branching filaments
B. Cell wall with inner cellulose layer, gelatinous pectic layer containing algin.
C. Motile cells with 2 different flagellae
D. Chloroplasts with high proportion of carotenaids to chlorophyll.(a and c) several xanthophylls includiog fucoxanthins. Chloroplasts variable, but usually discoid.
E. Food reserves laminarin & mannitol, sometimes fats
II. Distr.
5600 spp., mostly marine, commonest along cool sea shores, intertidal and subtidal zones.
III. Structure
A. Size - few are microscopic, most much larger - up to 150' . Larger forms with complex structure.
B. Cell wall - "Algin" - outer pectin layer is major component
C. Tissues - some specialization seen here. Tissues are groups of similar cells with similar function. Tissues with essentially similar cells - simple tissues, different types of cells contribute to similar function - complex tissues. Groups of tissues making up a morphologically and often functionally distinct part of organism - organ. Many brown algae have different tissues & have stem-like, root-like, leaf-like organs. Since they do not have vascular systems, these structures are not true stems, roots, or leaves. Termed rhizoid, stalk or stipe, caulalia, and phyllidia. Tissues which are relatively unspecialized- parenchyma. Usually thin-walled, often isodiametric. Most photosynthetic tissues are of this kind. Tissue char. by cell division - meristem.
IV. Life cycle
Most forms with distinct alternation of generations.
General life cycle-
One class, including Fucus has the gametophyte generation greatly reduced, and not an independent plant.
V. Representative genera.
A. Ectocarpus
Commonly found as an epiphyte of larger brown algae. Often very much branched. Isomorphic alternation of generation, L.c. essentially as above.
B. Laminaria - kelp
Mature sporophyte with distinct holdfast, stipe & blade.
Stipe erect, unbranched, XS with 3 parts
1. medulla, - some cells of which are conducting cells.
2. Cortex - with mucilaginous cells.
3. Epidermis.
Sporangia produced on both surfaces of blade - n zoospore - 32 or 64 - microscopic gametophytes, 1/2 zoosp. - Male gametophyte, 1/2 - female gametophyte syngamy - zygote - sporophyte. (Heteromorphic alt. of gen.)
C. Macrocystis - giant kelp.
D. Nereocystis
E. Postelsia palmiformis - Monterey
F. Fucus
Diploid thallus, gametophyte essentially non-existent. Only haploid portion - "gametes" - actually spores acting as gametes. Sporangia or gametangia borne in conceptacles scattered over receptacles,
G. Sargassum
tropical & subtropical. Attached or freefloating. Sargasso Sea L.C. Similar to Fucus
VI. Economic importance
A. Fertilizer
B. Burn, recover potassium & iodine No longer profitable.
C. Food - esp. Japan
D. Source of algin - stabilizer & moisture retainer in many products such as ice cream, cake frosting, paint, pharmaceutials, & processing of natural & synthetic rubber.
http://www.cs.cuc.edu/~tfutcher/Phaeophyta.html
l Rank
