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Plastid

Plastids are the organelles in plants and algae in which photosynthesis occurs. They also are critical in starch and other product storage, and in the synthesis of fatty acids, terpenes, and other molecules used as cellular building blocks and critical components to plant function. Plastids are divided into several types depending on morphology and function: chloroplasts, leucoplasts, amyloplasts, and chromoplasts. One plastid may have the ability to morph into another type of plastid.

Undifferentiated plastids may develop into amyloplasts (starch storage); chloroplasts (photosynthesis); etioplasts (chloroplasts that have not been exposed to light); elaioplasts (fat storage); chromoplasts (pigment synthesis and storage); and leucoplasts (synthesis of monoterpene). Plastids contain their own genome, like mitochondria do. Typically, the genome contains around a hundred genes that encode ribosomes and RNAs as well as photosynthetic proteins.

In algae, a different type of leucoplast makes up all unpigmented plastids; the other types of plastids do not occur in algae. Algal plastids sometimes also contain pyrenoids, unlike plant plastids.

Plastids are divided into three evolutionary lineages: green plastids are chloroplasts, red plastids are rhodoplasts, and blue-green plastids are the cyanelles. There are several differences in primary structure of these plastids as well as in pigmentation.

Web Resources On Plastid

Plastid Transformation
Plastid Molecular Genetics

Book Resources On Plastid

Plastids by Simon Geir Moller (Ed)
Origins Of Plastids : Symbiogenesis, Prochlorophytes and the Origins of Chloroplasts by Ralph A. Lewin

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