Plant tissue into a series of increasing concentrations of sucrose or mannitol solution, after a certain period of time to achieve osmotic equilibrium, the cells in which the critical mass-wall separation of the solution osmotic potential is equal to the osmotic potential of the cytosol. This solution is called isotonic solution, its concentration is called isotonic concentration. In practice, according to the concentration of the solution that causes critical mass wall separation and the average of the concentrations of neighboring solutions that do not cause mass wall separation, the isotonic concentration is calculated, and the osmotic potential of the solution is calculated, that is, the osmotic potential of the cell.
Operation method
An experiment to determine the osmotic potential of plant tissues
Principle
Plant tissue into a series of increasing concentrations of sucrose or mannitol solution, after a certain period of time to achieve osmotic equilibrium, the cells in which the critical mass-wall separation of the solution osmotic potential is equal to the osmotic potential of the cytosol. This solution is called isotonic solution, its concentration is called isotonic concentration. In practice, according to the concentration of the solution that causes critical mass wall separation and the average of the concentrations of neighboring solutions that do not cause mass wall separation, the isotonic concentration is calculated, and the osmotic potential of the solution is calculated, that is, the osmotic potential of the cell.
Materials and Instruments
Onion bulbs Purple duckweed blades Move I. Materials and equipment For more product details, please visit Aladdin Scientific website.
Microscope, blades, pipettes, petri dishes, tweezers.
Plant material: onion bulbs, purple duck toe grass leaves.
Equipment: microscope, razor blade, pipette, 6 cm diameter Petri dish, forceps.
Reagents: 1.00 mol sucrose solution or mannitol solution.
Experimental Steps
1, 1.00 mol of sucrose solution as the mother liquor, with distilled water diluted into 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60 mol solution, shaking well and ready for use.
2, with a razor blade on the inner epidermis of onion bulbs cut out the side length of 2-5mm small square, with tweezers to peel off the epidermis. Pay attention to the thickness of the torn off epidermis should be appropriate.
3, since the high concentration of the solution, every certain time (such as 3min), in order to the concentration of decreasing sucrose solution into the 4-5 pieces of epidermal blocks (epidermal tear immediately into the solution), so that the epidermis is completely immersed in the solution. 15-20min, starting from the highest concentration of sucrose solution, according to the original order of the epidermis into the removal; in the slide drop 1-2 drops of the corresponding concentration of sucrose solution, and then remove the epidermis. After 15-20 min, remove the epidermis in the order in which it was placed, starting with the highest concentration of sucrose solution; place 1 or 2 drops of the appropriate concentration of sucrose solution on the slide, and observe several fields of view under a microscope to record and calculate the separation of the plasmodesmata. Find the concentration of sucrose solution that causes about 50% of the cell protoplasm to just separate from the cell wall at the corners of the cell wall; and the highest concentration of sucrose that causes less than 50% of the cells to undergo plasmodesmosis or not to undergo plasmodesmosis.
4. Reformulate the two concentrations of sucrose solutions for the above results and repeat the experiment 1-2 times with new epidermis until the results meet the requirements. The average value of the osmotic potential of these two sucrose solutions is the osmotic potential of the cytosol.