MadSci Network: Cell Biology |
Chromoplasts and leucoplasts are members of a dynamic group of plant cell organelles called plastids. Plastids have distinct and specialized metabolisms and structures. Yet these organelles originate from the same precursor structure, proplastids, and are interconvertible depending on the environment and requirements of the plant cell.
It is interesting that plastids are theorized to have been free-living procaryotic organisms that became involved in a symbiotic relationship with primitive plants millions of years ago. Plastids have their own circular DNA that replicates and is similar to present day procaryotes.
Chloroplasts are the most familiar plastids. These contain the green photosynthetic pigments, chlorophyll, used by plants to harvest energy from the sun.
Amyloplasts are storage organelles. Starch that is stored on a permanent basis, more than a few hours, is found in these plastids.
Chromoplasts are found in many flower petals and fruits. These are the non-photosynthetic pigments (reds, oranges, purples, blues) known as carotenoids and xanthophylls.
Elaioplasts are the storage organelles of plants that produce oils.
Leucoplasts are plastids that are basically colorless and may not have specific functions.
Etioplasts are plastids that have developed when plants are grown in the dark and have no chlorophyll. When thes plants are exposed to light the etioplasts become fully functional chlorplasts with chlorophyll. This is a good example of the interconvertible nature of plastids.