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

But because the young Poins sat always silent with his eyes on the road to Ardres and slept—being privileged because he was yeoman of the King's guard—always in the little stone guard cell of the gateway at nights; because, in fact, the young man's whole faculties were set upon seeing that Thomas Culpepper did not pass unseen through the gate, it was four days before the gatewarden contrived to get himself asked why he would have spat in the dust or cast his hat on high.

From Project Gutenberg

Now," he said to the guards, "you had better take that fellow out and put him in the guard cell, the cold air will bring him round as soon as you get him out of this room.

From Project Gutenberg