Roots

Roots are underground plant organs that anchor the shoot system, absorb water and minerals, and store carbohydrates. Most vascular plants produce primary roots from the seed’s radicle, while many monocots develop adventitious roots. Some roots also function in vegetation reproduction.

Anatomy: The root tip is protected by the root cap, then the apical meristem, followed by zones of elongation and maturation. The outer epidermis, often with root hairs, absorbs water. The cortex stores resources, while the endodermis, with the Casparian strip, regulates radial transport into the stele, which contains xylem and phloem. The pericycle can give rise to lateral roots.

Root systems vary: taproots with a dominant central root and lateral branches (typical in many dicots) versus fibrous systems of many monocots. Adventitious roots arise from non-root tissues. Specializations include prop roots for support, pneumatophores for gas exchange, and storage roots such as carrots, beets, and potatoes.

Ecology and interactions: Roots form symbioses with mycorrhizal fungi to enhance nutrient uptake and, in legumes, with Rhizobium bacteria to fix atmospheric nitrogen in nodules. They influence soil structure, contribute to carbon storage, and respond to gravitropism and hydrotropism.

Human uses and importance: Root crops provide calories and nutrients; roots also stabilize soil and support ecosystem services. Root anatomy and physiology underpin many agricultural practices and environmental management strategies.