II. Two basic root cites are distinguished:

Taproot System: The first root to emerge from a seed is the radicle or primary root.

• In most dicots, the radicle enlarges and forms a prominent tap root.
• Smaller branch (lateral) roots grow from the taproot.
• A taproot system is common in conifers and dicots.
• It functions as food reserves such as carbohydrate storage or for reaching water deep in the ground.
• Taproots usually control growth and development of branch roots. Taproots grow longer than branch roots.

Fibrous Root System: Most monocots have a fibrous root system consisting of an extensive mass of similarly sized roots. In these plants, the radicle is short lived and is replaced by a mass of adventitious roots which are roots that form on organs other than roots; for example the stem. Because the adventitious roots of monocots are so extensive and cling to soil particles, such plants are excellent for preventing erosion.

Adventitious Roots: The adventitious roots of most monocots begin to grow soon after the seed germinates.

• Each node in the embryo usually produces 2-6 seminal roots that grow from the seed.
• These roots are soon supplemented by a system of crown roots that grow from nodes of the shoot.
• Recent studies of monocot systems tell us they are more complex than originally thought.
• Corn plants have two types of adventitious roots, one of which is usually unbranched and has actively growing tips. These feeder roots are associated with a 1mm-thick soil sheath permeated by root hairs and cemented together by secretions of the root and the soil's microbes.
• Other roots of the root system are long, branched, and lack an encasing soil sheath. These roots lack actively growing tips; they grow determinately.
• There are several types of adventitious roots besides those of monocots. These roots are common along rhizomes of ferns, clubmosses, and horsetails. In a lot of plants, adventitious roots are a primary means of vegetative reproduction; prairie grasses and forests of aspen are often a single clone spread by adventitious roots.
• The formation of adventitious roots is controlled by hormones such as auxin, which are the active ingredients in the rooting compounds sold in stores.
• Primary roots and adventitious roots have similar function and structure.