Experiments on the effect of potassium ions on stomatal openings

Summary

The expansion and contraction of the guard cells on both sides of the stomata directly affects the opening and closing of the stomata, which significantly influences the physiological processes of photosynthesis and transpiration in the leaf. The inorganic ion uptake theory of stomatal movement suggests that stomatal movement is mainly due to K+ regulation of the osmotic system of the guard cells. The purpose of this experiment was to understand the effect of potassium ions on stomatal opening.

Principle

The basic principle of the experiment on the effect of potassium ions on stomatal opening is that the osmotic system of guard cells can be regulated by potassium ions. With the participation of ATP, the potassium-hydrogen ion exchange pump on the protoplasmic membrane of the guard cell causes the guard cell to take up potassium ions from the surrounding epidermal cells against the difference in ionic electrochemical potentials, which reduces the osmotic potential of the guard cell, and thus opens the stomata. The degree of opening and closing of stomata has a very close relationship with the accumulation of ^K+ in guard cells, non-cyclic photosynthetic phosphorylation or cyclic photosynthetic phosphorylation to form ATP, the guard cell plasma membrane with light-activated ^H+ pumps, ^H+ pumps hydrolyze ATP, the use of the release of energy will be H+ secretion to the cell wall, the opening of inward ^K+ ion channels, the transfer of external ^K+ into the guard cell, thereby lowering the water potential of the guard cell, water uptake and expansion, so that the stomata open. The stomata open.

Operation method

Experiments on the effect of potassium ions on stomatal openings

Principle

Stomata are the main channel and regulator of water and gas exchange between terrestrial plants and the external environment. It has to let the CO2 needed for photosynthesis pass through, but also to prevent excessive water loss, so the distribution, density, shape, size, and opening and closing of stomata on the leaf significantly affect the leaf photosynthesis, transpiration and other physiological processes. When studying the effects of chemicals and factors on stomatal movement, it is often necessary to observe or measure the degree of stomatal opening and closing. Stomatal MovMent (stoMatal MovMent) and the defense cell accumulation of K + has a very close relationship, photosynthetic phosphorylation to form ATP, the defense cell plasma membrane with light-activated H + pump, H + pump hydrolysis of ATP, the use of the release of energy will be secreted to the cell wall, inward K + ion channels open, the outside of the K + transfer into the defense cell, thus reducing the defense cell water potential, water absorption The stomata are opened by swelling. In this experiment, we observed the stomatal changes by artificially increasing the K+ concentration. The stomata of plant leaves opened in the light and closed in the dark. Stomatal morphology, size and stomatal opening can also be observed directly under a microscope.

Materials and Instruments

Fava bean leaves
KCl Tris-HCl buffer
Microscope Tweezers Coverslips Slides Knives Droppers Liquid tubes Petri dishes

Move

1. Take 4 petri dishes numbered, take 2 of them and prepare 250 M M, 5O MM KCl solution 2 ml (diluted with Tris-HCl buffer); take the other 2 petri dishes and add 2 ml Tris-HCl buffer to them respectively and leave them for use.

2. Tear 2-3 MM ² of broad bean leaf epidermis into the above 4 petri dishes respectively, and put 3-4 pieces in each petri dish.

3. Place one Petri dish with Tris-HCl buffer into the drawer of the laboratory bench and leave it in the dark for 1.5 hours, and the other three Petri dishes under fluorescent light for 1.5 hours.

4. Remove the leaf epidermis from the different treatments and place them on slides, cover slips and observe the stomatal opening under a microscope.

Caveat

Observe and compare the opening of epidermal stomata in different treatments and explain why.

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