2007-12-02 15:19:23 · 2 answers · asked by Lola S 1 in Science & Mathematics ➔ Botany
The simplest explanation is this: Guard cells have chloroplasts while other epidermal cells do not. Therefore, guard cells make sugars during the light while the rest of the epidermal cells do not make sugars. Because of the extra sugars in the guard cells, water diffuses into the cells and causes the guard cells to swell. The guard cells have thicker cell walls on the inner (stoma) surface, and that thicker side doesn't "stretch out" as the cell swells up. The other sides do stretch out a bit. This makes the guard cells change shape from oval to curved, and the stoma is open.
See a picture here. http://www.cneccc.edu.hk/subjects/bio/album/Chapter12/STOMA_OPEN.html
2007-12-02 17:17:35 · answer #1 · answered by ecolink 7 · 0⤊ 0⤋
Guard cells open and close to allow gas exchange through the stoma.
2007-12-02 23:25:35 · answer #2 · answered by admode 3 · 0⤊ 0⤋