Heterocyst (Simplified)
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...