Plastids are a category of plant cell organelles which store materials for the plant. All plants possess some form of plastid, and only plants possess them. All plastids are double-membrane organelles; some plastids have three membranes.
Plastids include several kinds of organelles which share developmental homologies. All of them are developmentally related as they start out as proplastids, which eventually differentiate into specific plastids; due to this homology, they can also convert into another kind of plastid based on the plantβs needs, even after maturation.
The most well-known organelles are chloroplasts; other plastids include chromoplasts, leukoplasts, and amyloplasts. Each plastid stores different kinds of nutrients and materials which support the plantβs metabolism and growth.