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, a complex, discrete green structure, or organelle, contained in the cytoplasm of plant cells. Chloroplasts are reponsible for the green color of almost all plants and are lacking only in plants that do not make their own food, such as fungi and nongreen parasitic
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a cell organelle of many algae and of Hepaticae (mosses) of the order Anthocerotales. Pyrenoids, which are rounded or angular in outline, are located in or on the chloroplast. They are always closely associated with the chloroplast and serve as the site of starch formation. The size and number of pyrenoids may change with the age of the cell. The pyrenoid consists of a central protein body—the stroma—and a starchy covering (some pyrenoids lack this covering). The stroma of the pyrenoid, like that of the chloroplast, is finely granular; however, its consistency is more solid. It has embedded lamellae consisting of a continuation of more or less reduced lamellar system of the chloroplast. New pyrenoids arise as new formations or as a result of binary fission or fragmentation. The presence or absence of pyrenoids is a taxonomic characteristic.