What controls the opening and closing of pores?

The opening and closing of stomata is controlled by guard cells on leaves. Normal epidermal cells have no chloroplasts, but there are chloroplasts in guard cells, which can use sunlight for weak photosynthesis. Other factors of guard cells can adjust the expansion and contraction of guard cells and control the opening and closing of stomata.

There are some secondary guard cells on both sides of the guard cells. Guard cells and surrounding cells, including the existence of secondary guard cells, the shape and number of secondary guard cells, can form various types, so they can be used as one of the basis for identifying plant species.

Extended data

Appearance characteristics: The guard cells of dicotyledonous plants are generally half-moon-shaped, while those of monocotyledonous plants such as Gramineae are like a pair of dumbbells. The cell wall of guard cells is uneven in thickness, and the half-moon cells are connected with the convex surface of epidermal cells, and the wall is thin and elastic. Near the concave surface of the hole, the wall is thick and elastic.

When the swelling pressure increases, the thin wall extends outward, the thick wall rarely extends, the whole cell is curved, and the stomata open when there is an oval gap between the two cells; When the swelling pressure drops, the cells contract, the thick wall is tight, and the stomata are closed. The cell wall of dumbbell-shaped guard cells is thin at both ends and thick in the middle. When the expansion pressure is high, the two ends expand first, then the paired cells are separated from each other and the stomata are opened.

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