Plastids

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The plastid (Greek: πλαστός; plastós: formed, molded – plural plastids) is a major double-membrane organelle [1] found, among others, in the cells of plants and algae. Plastids are the site of manufacture and storage of important chemical compounds used by the cell. They often contain pigments used inphotosynthesis, and the types of pigments present can change or determine the cell's color. They have a common origin and possess a double-stranded DNA molecule, which is circular, like that of prokaryotes. Those plastids which contain pigments can carry out photosynthesis. Plastids can also store products like starch and can synthesisefatty acids and terpenes, which can be used for producing energy and as raw material for the synthesis of other molecules. For example, the components of the plant cuticleand its epicuticular wax, are synthesized by the epidermal cells from palmitic acid, which is synthesized in the chloroplasts of themesophyll tissue.[2] All plastids are derived from proplastids which are present in themeristematic regions of the plant. Proplastids and young chloroplasts commonly divide by binary fission, but more mature chloroplasts also have this capacity. plants, plastids may differentiate into several forms, depending upon which function they play in the cell. Undifferentiated plastids (proplastids) may develop into any of the following variants: Chloroplasts green plastids: forphotosynthesis; see also etioplasts, the predecessors of chloroplastsChromoplasts coloured plastids: for pigment synthesis and storageGerontoplasts: control the dismantling of the photosynthetic apparatus duringsenescenceLeucoplasts colourless plastids: formonoterpene synthesis; leucoplasts sometimes differentiate into more specialized plastids:Amyloplasts: for starch storage and detecting gravityElaioplasts: for storing fatProteinoplasts: for storing and modifyingproteinTannosomes: for synthesizing and producing tannins and polyphenols Depending on their morphology and...
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