guard cell

American  

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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guard cell British  

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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guard cell Scientific  

/ 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.

2. See more at stoma

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Etymology

Origin of guard cell

First recorded in 1870–75

Example Sentences

These are the long-known guard cell anion channels SLAC1 and SLAH3, whose activation, however, also requires the presence of calcium.

From Science Daily • Dec. 15, 2023

The second messengers NO and Ca2+ in the signal response to changes in the concentrations of these hormones activate transcription factors that affect ion transport across guard cell membranes.

From Textbooks • Jun. 9, 2022