Ergastic substances are non-protoplasm materials found in cells. The living protoplasm of a cell is sometimes called the bioplasm and distinct from the ergastic substances of the cell. The latter are usually organic or inorganic substances that are products of metabolism, and include crystals, oil drops, gums, tannins, resins and other compounds that can aid the organism in defense, maintenance of cellular structure, or just substance storage. During the lifetime of a cell, these can appear and disappear, indicating some level of participation in life processes. Ergastic substances may appear in the protoplasm, in vacuoles, or in the cell wall.
Although proteins are the main component of living protoplasm, proteins can occur as inactive, ergastic bodies—in an amorphous or crystalline (or crystalloid) form. A well-known amorphous ergastic protein is gluten.
Fats and oils
- Raphides are a type of elongated crystalline form of calcium oxalate aggregated in bundles within a plant cell. Because of the needle-like form, large numbers in the tissue of, say, a leaf can render the leaf unpalatable to herbivores (see Dieffenbachia and taro).