Summary
Roots help to anchor a plant, absorb water and minerals, and serve as storage sites for food. Taproots and fibrous roots are the two main types of root systems. In a taproot system, a main root grows vertically downward with a few lateral roots. Fibrous root systems arise at the base of the stem, where a cluster of roots forms a dense network that is shallower than a taproot. The growing root tip is protected by a root cap. The root tip has three main zones: a zone of cell division (cells are actively dividing), a zone of elongation (cells increase in length), and a zone of maturation (cells differentiate to form different kinds of cells). Root vascular tissue conducts water, minerals, and sugars. In some habitats, the roots of certain plants may be modified to form aerial roots or epiphytic roots.
Glossary
adventitious root
aboveground root that arises from a plant part other than the radicle of the plant embryo
Casparian strip
waxy coating that forces water to cross endodermal plasma membranes before entering the vascular cylinder, instead of moving between endodermal cells
endodermis
layer of cells in the root that forms a selective barrier between the ground tissue and the vascular tissue, allowing water and minerals to enter the root while excluding toxins and pathogens
fibrous root system
type of root system in which the roots arise from the base of the stem in a cluster, forming a dense network of roots; found in monocots
pericycle
outer boundary of the stele from which lateral roots can arise
root cap
protective cells covering the tip of the growing root
root hair
hair-like structure that is an extension of epidermal cells; increases the root surface area and aids in absorption of water and minerals
stele
inner portion of the root containing the vascular tissue; surrounded by the endodermis
tap root system
type of root system with a main root that grows vertically with few lateral roots; found in dicots