Brown seaweed: a brief description of the department

Brown algae are a numerical group of plants that live mainly in marine waters. To date, only eight species are known, which, in the course of evolution, have shifted to a freshwater environment.

Department of Brown algae: body structure

All representatives of this department have multicellular bodies - colonial and unicellular forms of existence have not been identified. As for the sizes, they can be very different - the thalli can be either microscopic or reach several meters in length. There are annual marine plants, but there are also those who live up to the age of 18.

If we talk about the shape and structure of the thalli, then there is also diversity. The body of the alga can consist of threads, plates, pouches, crusts or small shrubs. To the substrate the plant is attached either with the help of the sole, or with the system of rhizoids.

The integument covers are represented by a cell wall, which, as a rule, consists of two layers (there are also three-layer representatives). The outer, cover layer consists mainly of pectic substances, and also contains sulfated polysaccharides. The inner layer contains the bulk of cellulose fibers.

Algae Seed: cell structure

An important systematic characteristic of the cell is the presence of plastids. In the representatives of this group of plants, each cell contains a large number of small, well-developed chloroplasts. Plastids have four membranes. As a rule, the outer membrane of the chloroplast passes into the membrane of the nucleus or endoplasmic reticulum. As for chlorophyll, here it is represented by forms A, C1 and C2.

In addition, the plastids of algae contain fucoxanthin, violaxanthin, zeaxanthin and beta-carotene, which is also an important characteristic for systematics of plants.

The cell nucleus is only one, although some polynuclear species are also known. The main reserve product is chrysolaminarin, which is deposited in specialized vacuoles or in the form of cytoplasmic granules.

Brown algae and reproduction

Representatives of this department can reproduce in a vegetative, sexual and asexual way. In most species, vegetative reproduction is carried out by dividing the thallus. But, for example, in the ficus on the sole of the body there is a group of specialized cells, which, if necessary, can be transformed into a new thallus.

As for the asexual process, it is most often performed with the help of zoospores. Only some species multiply by immobile mono- or tetraspores. By the way, zoospores and gametes are the only flagellated forms of existence of brown algae.

As for the sexual process, it can be:

• Isogamous (spermatozoa and ovules are the same size).
• Heterogamous (male and female gametes have different gametes).
• Oogamous (male gametes are small and mobile, while female oogones remain immobile and are large in size).

Approximately in the 80s of the 20th century, certain chemical substances were detected by the algae organism during sexual development. This is nothing but pheromones, the active study of which continues to this day.

Brown algae and the most famous representatives

One of the most famous species is laminaria sugar, or sea kale. The plant has a large dismembered thallus, the length of which can be from 1 to 14 meters. In the thallus accumulates a huge amount of laminarin. In addition, sea kale is considered a valuable source of iodine. In some countries, this plant is actively cultivated and used for cooking salads and other dishes. From talom also make drugs used in the treatment of diseases of the thyroid gland.

The Sargassum family is also widely known, because it was due to the long, sturdy thallus of these plants that the waters of the Sargasso Sea were too dangerous to swim in due time.