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guard cell

noun Botany.
  1. either of two specialized epidermal cells that flank the pore of a stoma and usually cause it to open and close.
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Origin of guard cell

First recorded in 1870–75
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for guard cell

guard cell

noun
  1. botany one of a pair of crescent-shaped cells that surround a pore (stoma) in the epidermis. Changes in the turgidity of the cells cause the opening and closing of the stoma
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Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

guard cell in Science

guard cell

[gärd]
  1. One of the paired cells in the epidermis of a plant that control the opening and closing of a stoma of a leaf. When swollen with water, guard cells pull apart from each other, opening the stoma to allow the escape of water vapor and the exchange of gases. When drier, guard cells become more flaccid and move closer together, allowing the plant to conserve water. Unlike the other cells in the epidermis, guard cells have chloroplasts and conduct photosynthesis. See more at stoma.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.