SCIENCE TEMPO

Heterocysts are specialized, thick-walled cells that can be found in the trichomes of blue-green algae. They earn their name because they are distinct from regular vegetative cells. These cells appear pale-yellow in color. There are two types of heterocysts: Terminal heterocyst: Located at the terminal end of the trichome. Intercalary heterocyst: Positioned between the vegetative cells of the trichome or laterally. Heterocysts develop from vegetative cells that enlarge and transform into proheterocysts before eventually becoming heterocysts. The envelope of a heterocyst is exceptionally thick, consisting of two layers—the outer sheath and the inner cell wall. The sheath is further divided into three layers: an outer fibrous layer, a middle homogeneous layer, and an inner laminated layer. This sheath envelops the heterocyst, leaving only the junction between the heterocyst and the adjacent vegetative cell exposed. The heterocyst's cell wall consists of four layers: L1, L2, L3, and L...

Nostoc is a prokaryotic, unbranched, filamentous, colonial blue-green alga belonging to the class Cyanophyceae. It is commonly known as star jelly, witches' butter, or mars egg. This alga is found in both aquatic and terrestrial habitats and exists in a haploid form. The colony of Nostoc is globular and jelly-like, ranging in size from that of a pea seed to a plum fruit. It is surrounded by an outer firm gelatinous layer called the pellicle, which encloses a gelatinous matrix. The center of the colony remains hollow. Within the gelatinous matrix, numerous filaments are present, with each filament referred to as a trichome. These filaments are enclosed by a mucilage sheath and consist of oval cells. The trichome is composed of three types of cells: Vegetative cells Heterocysts Akinetes Each cell is bounded by an outer cell wall and an inner plasma membrane. The cell wall is primarily composed of hemicellulose and pectin, while the plasma membrane encloses the protoplasm. The protopl...

Oscillatoria is a freshwater blue-green algae belonging to the class Cyanophyceae. It is a prokaryotic organism. The vegetative thallus is a haploid gametophyte. The alga is named Oscillatoria because the tip of the trichome exhibits pendulum-like oscillating movement. The thallus consists of an unbranched trichome with uniseriate filaments surrounded by a mucilaginous sheath. The trichome is composed of closely arranged uniform cells, and the terminal cell has a thickening at the apex known as a cap or calyptra. The filament contains necridia and hormogone. Each cell in the filament is structured with an outer cell wall, a middle plasma membrane, and an inner protoplasm. The cell wall is composed of pectin and cellulose, with the plasma lying beneath it. The protoplasm is differentiated into an outer chromoplasm and an inner centroplasm containing pigments, pseudovacuoles, thylakoids, and reserve food materials, such as Cyanophycean starch and B-granules. The nuclear material in Oscil...

Habitat: Algae are predominantly found in aquatic or moist environments Thallus Structure: Algae can exist as either unicellular or multicellular organisms, with their plant body termed thallus. However, this thallus lacks differentiation into roots, stems, and leaves. Chlorophyll and Photosynthetic Pigments: Chromatophores within the thallus harbor chlorophyll and other photosynthetic pigments. Autotrophic Nutrition: Algae are primarily autotrophic, synthesizing their food through photosynthesis. Cell Type: Algal cells can be prokaryotic or eukaryotic. Nuclei: Algal cells may contain either a single nucleus (uninucleate) or multiple nuclei (multinucleate). Cell Wall Composition: The algal cell wall is rich in cellulose, providing structural support. Motility: Certain algal cells possess mobility due to the presence of cilia or flagella. Reserve Food: Starch serves as the common reserve food in algae. Reproduction: Primitive algae undergo vegetative reproduction, while higher forms exh...