Chromoplast

chromoplast [′krō·mō‚plast]

(cell and molecular biology)

Any colored cell plastid, excluding chloroplasts.

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Chromoplast 

a pigmented intracellular organelle of plant cells; a type of plastid. Chromoplasts may be spherical, spindle-shaped, sickle-shaped, or irregularly polygonal. Their orange, yellow, or brownish coloring is caused principally by carotenoids. Chromoplasts are usually formed from green plastids—chloroplasts—as green chlorophyll pigments are destroyed in the process of the ripening of the fruits of certain plants, such as mountain ash, lily of the valley, and persimmon, and during the autumn yellowing of leaves. At this stage the protein-lipid membrane of the chloroplast system decomposes. The protein flows out of the plastids, while the lipid remains inside, dissolving the carotenoids, which color the plastids orange and yellow. In some instances the chromoplasts are formed from colorless plastids—leukoplasts—for example, in carrot roots.

REFERENCES

See references under PLASTIDS.