All eukaroytic cells are divided into separate compartments, each surrounded by an independent membrane system. These compartments are called organelles, and they include the nucleus, mitochondria, vacuoles, Golgi bodies, endoplasmic reticulum, and microbodies. In addition to these organelles, plant cells contain a compartment that is unique to them. This is the plastid.

General Description of Plastids

Plastid is a term applied to an organelle that is exclusive to plant cells. Most of the compounds important to a plant, and to human diet, start out in the plastid. It is the place in the cell where carbohydrates, fats, and amino acids are made. As the name suggests, the plastid is plastic (i.e., changeable) in both appearance and function, and the different types of plastids can change from one type to another. The signals that trigger these changes can come from within the plant itself (e.g., developmental changes...