"Phaeophyta Fucus receptacle 03" by Bruce Kirchoff is licensed under CC BY 2.0
Definition of Phaeophyta (Brown Algae)
Brown algae are plant-like protists that have many-celled thallus, so they can be seen macroscopically (with the naked eye). The thallus has an adhesive device to attach its body to the substrate, while the rest of the body floats on the water. Some members of the Phylum Phaeophyta such as Sargassum, Macrocystis, and Nereocystis have air bubbles that function to store nitrogen gas and to float on the surface of the water.
Brown algae contain brown pigments (xanthophylls), chlorophyll a and c. The amount of xanthophyll pigment is dominant, causing the color of the thallus to be brown. Food reserves are stored in the form of laminarin. Generally, brown algae are multicellular (multicellular). Its body shape resembles higher plants because it has parts resembling roots, stems, and leaves, making this algae easy to identify.
About 1,500 species of Phaeophyta or brown algae are known. Almost all types of Phaeophyta live in the sea, especially in cold areas, which live on rocks at the bottom of the water as deep as 1.5 - 5 meters from the water surface. All brown algae are threads or sheets and are autotrophic (capable of producing their own food).
All Phaeophyta live in colonies with shapes varying from simple to large ones with complex cell organization. In large colonies of Phaeophyta, no real organs have yet been formed, although in some species there are shapes resembling roots, stems, and leaves, the whole part is referred to as a thallus.
Characteristics of Phaeophyta (Brown Algae)
Brown algae (Phaeophyta) have general characteristics or characteristics, which are as follows.
■ Core are eukaryotic cells because the cell nucleus already had membranes.
■ multicellular (multicellular).
■ Shaped sheet, and some even resembling a tall plant (Plantae) because it has a section resembling roots, stems, and leaves.
■ It has air bubbles that served as a float.
■ Had the talus microscopic to macroscopic size.
■ Have pigment chlorophyll a, chlorophyll c, violaxantin, b-carotene, diadinoxantin, as well as the amount xantofil dominant.
In the form of branched filaments, unbranched and some are erect.
■ Characteristically autotorof, because chlorophyll to perform photosynthesis.
■ Having a single chloroplast some thread-like disk-shaped (discoid).
■ The chloroplasts contain pirenois to store food reserves.
■ Backup stored food in the form of laminarin.
■ Have a cell wall.
■ In the cell wall and intercellular space are agen (alginate acid), the inside of the cell wall composed of cellulose layers.
■ Having a network of transportation such as higher plants.
■ Almost all types of Phaeophyta habitat in the ocean, especially in the cold, that live in the rocks in the bottom waters as deep as 1,5 - 5 meters from the water's surface.
■ All Phaeophyta live in colonies with varied shapes from the simple to the form of large (over 30 meters) with complex cellular organization.
Classification of Phaeophyta (Brown Algae)
■ Laminaria , has a stem, the leaf-shaped sheets, containing iodine and alginic acid.
■ Macrocystis , produces iodine and alginic acid that serves as an industrial material.
■ Sargasum , sheet-shaped leaves, between the stem and the stem there are air bubbles.
■ Fucus , leaf shape in the form of sheets and at the edges of the leaves are bubbles.
Methods of Reproduction of Phaeophyta (Brown Algae)
Reproduction in Phaeophyta is done asexually (vegetatively) and sexually (generatively). Brown algae asexual reproduction is done by fragmentation and formation of spores (aplanospores and zoospores). The resulting zoospores have flagella that are unequal in length and are located on the lateral side (sides or edges).
Meanwhile, sexual reproduction is done by isogamy , anisogamy , or oogamy . Fucus vesiculosis is an example of brown algae that reproduces oogamously. There is a way of generative/sexual reproduction of brown algae which is similar to higher plants, namely the ends of the fertile thallus sheets form a body containing reproductive organs called receptacles .
Inside this receptacle there is a conceptacle containing antheridia which produces male sex cells in the form of spermatozoa and oogonia which produce eggs (ova) and sterile threads called paraphysis. The antheridia are funnel-shaped cells that arise from the base and edges of the conceptacle, the oogonia are bodies that sit on top of the stalk.
If a spermatozoon can fertilize an egg, a zygote will be formed. The zygote then forms a thick wall of cellulose and pectin, then attaches to a substrate such as rocks, then grows into a new individual whose chromosomes are diploid.
Examples and Roles of Phaeophyta (Brown Algae) in Life
Many types of Phaeophyta are beneficial to humans. Some species produce human food. In other countries kelp is used for animal feed and fertilizer, because the nitrogen and potassium content is high but the phosphorus content is low. Phaeophyta also produce algin (alginic acid), a colloid that is useful as a stabilizer in the manufacture of ice cream. Algin is also important in the pharmaceutical industry, namely as an ingredient for making pills, tablets, ointments, and dental cleaning drugs.
Some examples of Phaeophyta are as follows.
■ Fucus vesiculosus , height can reach 30 - 100 cm, live attached to rocks that appear when water is low. There are air bubbles along the sides of the thallus that branch like a fork. The tip is enlarged to form a conceptacle.
■ Sargassum siliquosum , live attached to rocks along the rocky coast of the tropics. However, on the northern Atlantic coast, the species of Sargasssum natans floats freely on the sea surface. Sargassum sizes vary from small to hundreds of meters in length.
■ Macrocystis integrifolia or kelp , size is very large, on the west coast of North America are found in length can reach three kilometers. Living kelp is firmly attached to rocks with the help of a root-like thallus.
■ Laminaria sinclairii is a type of brown algae producer alginic acid needed for the production of textiles, food, and cosmetics.
■ Fucus serratus , including brown algae that differentiate into a form that floats.
■ Postelsia is an example that many common brown algae.
■ Turbinaria decurens , Dictyota sp ., Dictyosiphon sp ., Nereocystis sp . is another example of Phaeophyta species or brown algae.
