johnny root

Science Dictionary
root  [%PREMIUM_LINK%]     (rt, rt)  Pronunciation Key 
  1. A plant part that usually grows underground, secures the plant in place, absorbs minerals and water, and stores food manufactured by leaves and other plant parts. Roots grow in a root system. Eudicots and magnoliids have a central, longer, and larger taproot with many narrower lateral roots branching off, while monocots have a mass of threadlike fibrous roots, which are roughly the same length and remain close to the surface of the soil. In vascular plants, roots usually consist of a central cylinder of vascular tissue, surrounded by the pericycle and endodermis, then a thick layer of cortex, and finally an outer epidermis or (in woody plants) periderm. Only finer roots (known as feeder roots) actively take up water and minerals, generally in the uppermost meter of soil. These roots absorb minerals primarily through small epidermal structures known as root hairs. In certain plants, adventitious roots grow out from the stem above ground as aerial roots or prop roots, bending down into the soil, to facilitate the exchange of gases or increase support. Certain plants (such as the carrot and beet) have fleshy storage roots with abundant parenchyma in their vascular tissues. See also fibrous root, taproot.

  2. Any of various other plant parts that grow underground, especially an underground stem such as a corm, rhizome, or tuber.

  3. The part of a tooth that is embedded in the jaw and not covered by enamel.

  4. Mathematics

    1. A number that, when multiplied by itself a given number of times, produces a specified number. For example, since 2 × 2 × 2 × 2 = 16, 2 is a fourth root of 16.

    2. A solution to an equation. For example, a root of the equation x2 - 4 = 0 is 2, since 22 - 4 = 0.


The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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