Brown algae are the largest group of plants that are found mainly in the offshore waters.To date, only eight known species, which in the course of evolution moved in the freshwater environment.
Department Kelp: body structure
All the members of this department are multicellular body - colonial and unicellular forms of existence are not revealed.As for the size, they can be very different - like fronds can be microscopic, and reach several meters in length.Known annual marine plants, but there are those who live up to 18 years.
If we talk about the shape and structure of the thalli, there is also diversity reigns.The body can consist of algae filaments, plates, bags, crusts or small bushes.To the substrate is fixed or plant via sole or system rhizoids.
Integument presented the cell wall, which usually consists of two layers (there are also representatives of the sandwich).The outer cover layer consists essentially of pectin substances and also contains sulfated polysaccharides.The inner layer provides the bulk of the cellulose fibers.
Drills algae: cell structure
important systematic feature of cells is the presence of plastids.The representatives of this group of plants, each cell contains a large number of small well-developed chloroplasts.Plastids have four membrane.Typically, the outer membrane of the chloroplast membrane passes into the nucleus, or the endoplasmic reticulum.As chlorophyll here it contains the forms A, C1 and C2.
In addition, plastids of algae contains fucoxanthin, violaxanthin, zeaxanthin and beta-carotene, which is also an important characteristic for the systematics of plants.
cell nucleus is only one, although there are some multi-species.The main product is the spare hrizolaminarin that is deposited in specialized vacuoles or as cytoplasmic granules.
Brown algae and reproduction
Representatives of this department can be propagated vegetatively, sexually and asexually.In most species, cloning is carried out by dividing the thallus.But, for example, ficus on the sole of the body there is a group of specialized cells, which if necessary can be transformed into a new thawed.
As asexual process, it is most often carried out by means of zoospores.Only a few species reproduce by means of fixed mono or tetraspor.By the way, zoospores and gametes - the only form of existence flagellates kelp.
As for the sexual process, it can be:
- isogamous (sperm and eggs are the same size).
- heterogamic (male and female gametes have different gametes).
- Oogamnym (male gametes are small and mobile, while women oogonia remain stationary and different large size).
about in the 80s of the 20th century have been found certain chemical substances secreted by the body during sexual algae development.This is nothing like pheromones, active learning that lasts to this day.
Brown algae and most well-known representatives
One of the most known species is considered to be sugar kelp or seaweed.The plant has a large dissected thawed, the length of which can be from 1 to 14 meters.The thallus accumulated a huge amount of laminarin.In addition, seaweed is considered a valuable source of iodine.In some countries, this plant actively cultivated and used in salads and other dishes.From Tal also make the drugs used in the treatment of thyroid diseases.
genus Sargassum is also widely known as it is because of persistent, long thalli water these plants Sargasso Sea at the time were too dangerous for swimming.
