In plants one or more tissues combinedly discharge a common function in different parts and constitute a tissue system. Epidermal tissue system, fascicular tissue system and fundamental tissue systems are three principal systems in any plant. All these tissue systems owe their origin to promeristem.
Epidermal tissue system develops from protoderm, ground tissue system originates from ground meristem and vascular (or fascicular) tissue system originates from procambium. Epidermal tissue system includes epidermis, stomata, and epidermal out growths such as hairs, collectors, bladders, scales, and other emergences. This system helps in protection of the inner tissues in addition to some physiological function.
Ground tissue system includes cortex, pericycle, pith and medullary rays and mainly made up of parenchymatous cells. This system mainly helps in storage of water and food material and act as a packaging system. Vascular tissue system contains discrete units of vascular strands embedded in the ground tissue.
Each vascular strand contains xylem, phloem and with or without cambium. Vascular bundles are different types: radial, conjoint (collateral/or bicollateral), concentric. Stele is the central core of plant axis (stem or root) and includes the mass of tissue encircled by pericycle. Protostele is the most primitive stele from which other steles are derived. There are mainly 3 types of steles: protostele, siphonostele and Solenostele. Solenostele is the advanced and atactostele (found in monocot stems) is the most advanced type of stele.