Brown seaweed are the lowest sporous plants living mainly in salty water and leading the attached life. Characteristic representatives - a laminaria and a fucus.
Structure of a body of brown seaweed
Brown seaweed fasten to rocks and stones, the majority of types - sea. Types of structures of a body at brown seaweed: nitchaty, raznonitchaty, fabric. The Nitchaty body represents several one-nuclear branched threads. Raznonitchaty brown seaweed remind cords. The body of seaweed can be one-year and long-term. The body of fabric type of the building can have the different form: in the form of a sphere, in the form of a bag, a plate. Some brown seaweed have in a body bubbles which help to hold vertical position.
At less developed a body it is formed by two fabrics: bark and a core, at more developed – four: bark, meristodermy, intermediate fabric and core. Can raise brown seaweed in several ways. A diffusion way – the majority of cages can shares. Top – only top cages share. Trikhotallichesky – sharing, cages form hairs over a body. Intercalary – cells of fabric of a meristem accrue up and down. Meristodermatichesky — growth at the expense of special surface fabric.
Brown seaweed contain salts of alginic acid and pectinaceous substances. Because of it cellular covers can be in a gel state. In many countries the brown seaweed are actively eaten, they are rich with minerals. Cages at brown plants have 1 kernel. In cages the spare product – polysaccharide laminarin is postponed. Covers of cages contain cellulose.
Reproduction at brown seaweed can happen on the following types: vegetative, sexual, not sexual. Vegetative reproduction – at accidental fragmentation of a body of seaweed. Not sexual reproduction is characteristic of the majority of brown seaweed. It happens by means of mobile a zoodispute. Zoodisputes ripen in special cages after several nuclear fissions. In the external environment the zoodisputes actively move within several minutes then dump zhgutik and sprout on substrate. At the majority of brown seaweed during life cycle 2 generations alternate: the gametogophyte also sporofit. The gametogophyte reminds set of threads, its products are men's and female gametes. Merging, they give rise to a sporofit. Sporofit will give disputes from which the gametogophyte will develop subsequently. Brown seaweed have pheromones which help them with reproduction. They stimulate release of men's gametes and attract them to women's.