Idioblasts are isolated plant cells which differ from neighboring tissues and contain non-living substances. They have various functions such as storage of reserves, excretory materials, pigments, and minerals. They could contain oil, latex, gum, resin, tannin or pigments etc. Some can contain mineral crystals such as acrid tasting and poisonous calcium oxalate or carbonate or silica. Any of the tissue or tissue systems of plants can contain idioblasts.[1] Idioblasts are divided into three main categories: excretory, tracheoid, and sclerenchymatous.
Idioblasts can contain biforine cells that form crystals. The chemicals are excreted by the plant and stored in liquid or crystalline form. In bundles they are known as druse and as crystals they can be of raphide [needle] form. When the end of an idioblast is broken the crystals or other substance is ejected by internal water pressure. Ideoblasts of calcium oxalate appear to have no function other than a poisonous deterrent to herbivores.[2]