What can regulate the opening and closing of stomata and promote the flowering and fruiting of plants?

Opening and closing mechanism of stomata

The opening and closing of stomata is related to the water potential of guard cells. When the water potential of guard cells drops and absorbs water and expands, the stomata open, while the water potential rises and shrinks, so that the stomata close.

At present, there are several theories about the reasons for the decline and rise of water potential of guard cells.

1. starch sugar conversion theory.

Photosynthesis is necessary for stomatal opening. The guard cells of etiolated leaves have no chlorophyll, so they cannot carry out photosynthesis. Under the influence of light, stomatal movement does not occur. It has been observed for a long time that pH affects phosphorylase reaction (at pH 6. 1 ~ 7.3, starch hydrolysis is promoted; Promote starch synthesis at pH2.9~6. 1+0): According to the theory of starch sugar conversion, plants carry out photosynthesis to protect cells under light, which leads to the decrease of CO2 concentration and the increase of pH (about 5 ~ 7). Starch phosphorylase promotes the conversion of starch into glucose-1-P, and the intracellular glucose concentration is high and the water potential is reduced. When it is dark, photosynthesis stops. Due to the accumulation of CO2 and H2CO3 by respiration, the pH value decreases, and starch phosphorylase promotes the conversion of sugar into starch. The glucose concentration in guard cells is low, so the water potential increases, water is discharged from guard cells, and stomata are closed. Experiments show that leaves floating in high pH solution can open pores. On the contrary, it will cause the pores to close. But in fact, the transformation of starch and sugar in guard cells is quite slow, so it is difficult to explain the rapid opening and closing of stomata. The results showed that when the stomata just opened in the morning, starch disappeared obviously and glucose did not increase correspondingly. In the evening, after the stomata were closed, the starch did increase again, but the glucose content was also quite high. In addition, some plants (such as onions) have no starch in their guard cells. Therefore, it is unconvincing to explain the opening and closing of stomata with starch sugar conversion theory in some aspects.

2. Inorganic ion absorption theory.

According to this theory, the osmotic potential of guard cells is regulated by potassium ion concentration. ATP produced by photosynthesis is supplied to the guard cell potassium-hydrogen ion exchange pump to do work, so that potassium ions enter the guard cell, so that the water potential of the guard cell decreases and the stomata open. In 1967, M.Fujino of Japan observed that the potassium ion concentration of Commelina communis guard cells floating on the surface of KCl solution increased significantly and the stomata opened under light. When turning into darkness or turning into Na and Li under light, the stomata will close. Tearing off a piece of Commelina communis epidermis and floating in KCl solution, adding ATP can accelerate the opening of stomata under light, which shows that the potassium ion pump is started by ATP. It is proved by electron probe microanalyzer that potassium ions flow in open or closed pores, which can fully explain that the opening and closing of pores are related to the concentration of potassium ions.

3. Malic acid production theory holds that malic acid metabolism affects the opening and closing of stomata. Under light, the guard cells carry out photosynthesis, and the glucose converted from starch is converted into phosphoenolpyruvate (PEP) through glycolysis. At the same time, the CO2 concentration of guard cells decreased and the pH increased, and most of the remaining CO2 was converted into bicarbonate (HCO3). Under the action of PEP carboxylase, HCO3 and PEP combine to form oxaloacetic acid, which is then reduced to malic acid. Malic acid will produce H+, ATP will start the H-K exchange pump, protons will enter the secondary guard cells or epidermal cells, and K will enter the guard cells, so the water potential of the guard cells will drop and the stomata will open. In addition, the opening and closing of stomata is related to abscisic acid (ABA). When very low concentration of ABA was applied to leaves, stomata closed. Later, it was found that when the leaves were short of water, the ABA concentration in the leaves increased and then the stomata closed.

Main factors affecting stomatal movement

1 stomatal movement induced by light

The chloroplasts of guard cells photosynthesize under light, and the pH value in cells increases due to CO2. Starch phosphorylase hydrolyzes starch into glucose phosphate, which reduces the water potential in cells. CO2 produced by respiration in the dark reduces the pH value of guard cells, and starch phosphorylase synthesizes glucose into starch, so the concentration of cell fluid decreases, the water potential increases, the guard cells lose water and the stomata close. The osmotic system of guard cells can also be regulated by K, and the light reaction of photosynthesis (cyclic and acyclic photophosphorylation) produces ATP, which absorbs K by actively transporting counter-ion concentration difference, reduces the water potential of guard cells, and absorbs water to open stomata. Note: ① When the light intensity is lower than the light compensation point, the stomata are closed; ② Red light and blue-violet light have the best effect on the light quality that causes stomatal opening; ③ The stomata of Sedum plants are open at night, absorbing and storing CO2 (malic acid is stored in vacuoles), while the stomata are closed during the day, and malic acid is decomposed into pyruvate to release CO2 for photosynthesis.

2 carbon dioxide affects stomatal movement

Low concentration CO2 promotes stomatal opening, while high concentration CO2 makes stomatal close quickly, no matter in light or dark. The inhibition mechanism may be that the pH value of guard cells decreases, the water potential increases and the guard cells lose water. It will take some time for CO2 to be gradually consumed under light, and then the stomata will open quickly.

3 Temperature affects stomatal movement

Generally, the stomatal opening increases with the increase of temperature, reaching the maximum at about 30%. Although the stomata are exposed to light for a long time at low temperature (such as 10% or less), the stomata cannot be opened well, mainly because the activity of starch phosphorylase is not high. When the temperature is too high, transpiration is too strong, the guard cells lose water and the stomata are closed.

4. Leaf water content affects stomatal movement.

If the transpiration is too strong during the day, the stomata of the guard cells will be closed, and the leaves will be saturated with water in rainy days, and the epidermal cells will be squeezed by high water content, so the stomata will also be closed during the day.

5. wind

Breeze can promote the opening of stomata, because breeze can appropriately reduce the humidity around the leaves. Strong winds cause stomata to close.

6. Chemical substances

Phenylmercury acetate, atrazine (2- chloro -4- ethylamino -6- isopropylamino-triazine) and acetylsalicylic acid can inhibit stomatal opening and reduce transpiration. Spraying low concentration abscisic acid solution on leaves can inhibit stomatal opening for several days, and take effect quickly. Stomatal of many plants can start to close within 2 ~ 10 minutes. Cytokinin can promote stomatal opening.