Cyanophyta is division of Algae which includes class cyanophyceae or myxophyceae and the plants included in it are called blue green Algae because their pigment is bluish green. C-Phycocyanin. They are containing chlorophyll. They bear no well organised cell organelles. Pigments are present in chromoplasm. Nucleus is primitive type and takes nuclear membrane and nucleolus. They bear no flagella and they can move by gliding action. They are unicellular colonial in form cells are present in common gelatinous matrix. Filaments are unbranched and uniseriate or may sometimes show preudobranching. Their structure is prokaryotic. Cell wall is formed of micro fibrils held together in mucilage sheath. Orientation of fibres may vary in different species and may be reticulate as Nostoc.
Cell wall is differentiated into four layers. It is formed of mucopeptides, Carbohydrates, amino acids and fatly acids. Pain pigments are chlorophyll a, c Phycocyanin and c Phycocrythrin and they give blue green colour to algae.
Membrane bound plastids and absent. Pigments are found embedded within lamellae composed of two membranes joined at the ends. These algae show gliding jerky movements. Reserve food material is starch and protein. In Nostoc specialized structures called heterocyst are present. They may be terminal or inter calary in position as in Nostoc. Actual function of heterocyst is not known but are supposed to be centre of N2 – fixation. Reproduction takes place by vegetative and asexual methods. Vegetative reproduction takes place by cell division, fragmentation and hormogonia-formation. Asexual reproduction is by akinetes, endospores, exospores, heterospores and mannocytes e.g. Oscilaloria.
Plant body is filamcutons and unbranched. Filaments are called trichromes each of which has many cells places end to end. Each cell of the trichrome is rectangular. Cell wall has cellulose and pectin compounds. Below cell protoplast in present bearing perephral pigmented portion the chromoplasm and a central colourless region the central body or centroplasm. Chromoplasm contains pigments and reserve food material. There are no definite chromatophores, the pigments are irregularly distributed in it. The central body or Centroplasm or incipient nucleus is the nucleus without nuclear membrane.
ECONOMIC IMPORTANCE:
Mucilage is present which helps in the development and better nourishment for nitrogen fixing bacteria. Anebena and Nostoc are able to utilize and fix atoms pheric nitrogen and increase soil fertility. It has been seen that some members of Myxophyceae (Cyanophyceae) were able to fix 20 lbs of atmospheric nitrogen per acre in rice field. Rice increase was made from 15 to 20%.
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