What controls the opening and closing of the stomata

When I saw the problem, I thought it was a leaf... by light.

In general, plants close their stomata when the temperature is high, such as around 12:00. There are also plants that open their stomata at night, and there are more plants in the desert.

Closure is to reduce transpiration and water loss. It is opened to absorb carbon dioxide, the raw material for photosynthesis.

The switch of the stomata is related to the water potential of the guard cell, the water potential of the guard cell decreases and the water absorption expands, the stomata open, the water potential rises and the water loss shrinks, so that the stomata are closed. The causes of the decline and rise of the water potential of the guard cells are currently in the following theories:1

starch-glycoconversion theory; Inorganic ion absorption theory; The theory of malic acid production.

Stomata, one of the many small openings in the epithelium of leaves, stems and other plant organs, are structures unique to the epidermis of plants. Stomata are usually found in the aerial parts of plants, especially on the leaf epidermis, and can also be seen on young stems and petals, but most submerged plants do not.

In a narrow sense, the convex lens-like holes formed between guard cells are often called stomata. Guard cells differ from epidermal cells in that they contain chloroplasts in their structure, but they are smaller in size and less numerous, and their lamellar structure is underdeveloped, but they can photosynthesize and synthesize carbohydrates. It is sometimes accompanied by 2 to 4 paraguard cells adjacent to the guard cells.

The inclusion of these cells is a generalized stomata (or stomatal apparatus). Immediately below the stomata there is a wide intercellular space (air cell).

In the metabolism of gases such as carbon assimilation, exhalation and absorption, and transpiration, stomata become the passage of air and water vapor, and its passage is regulated by the opening and closing of guard cells, which is of great physiological significance.

The opening and closing of the stomata is controlled by guard cells on the leaf. Normal epidermal cells do not have chloroplasts, but there are chloroplasts in guard cells, which can use sunlight for weaker photosynthesis, plus other factors of guard cells, which regulate the expansion and contraction of guard cells, and can control the opening and closing of stomata.

There are also some paraguard cells on either side of the guard cell. Guard cells and surrounding cells, including the presence or absence of paraguard cells, the shape and number of paraguard cells, etc., can form various types, so they can be used as one of the bases for identifying plant species.

Mechanism of stomatal closure: stomatal motility is the result of altered turgor pressure within guard cells. This is caused by changing the water potential of the guard cells.

It has long been known that the opening and closing of the stomata is related to the alternation of day and night. When the temperature is right and the water is sufficient, the plants are moved from the dark to the light, and the water potential of the guard cells decreases, the water absorption expands, and the stomata open. During the day, when there is too much transpiration, the water supply is insufficient, or in the dark, the guard cells lose water and shrink due to the rising water potential, causing the stomata to close.

Closure of the stomata does not affect the respiration rate, the oxygen required for breathing is sufficient and the enzymes are in a state of high efficiency.

But photosynthesis is affected. Because the light is greater than the respiration at this time, the oxygen for respiration is enough, but the carbon dioxide for photosynthesis is not enough, closing the stomata reduces the absorption of carbon dioxide, thus affecting the photosynthetic rate.

Closing the stomata reduces the amount of carbon dioxide absorbed and weakens photosynthesis.

Reduced water absorption has little effect on the absorption of inorganic salts.