The water status of plant tissues can be expressed in terms of water potential. The magnitude of the water potential of plant tissues can, to a certain extent, reflect the water demand status of plants. Generally speaking, when the plant tissue water potential is low, it is a reflection of water demand, so in agricultural production, the measurement of the change in plant tissue water potential can be used as a reference index for irrigation.
When the plant tissue immersed in a variety of concentrations of solution, due to the exchange of water between the cells and solution, the solution concentration changes, the change in concentration caused by the change in specific gravity, therefore, when the immersed plant tissues of the solution drops back to the original corresponding solution, the droplets were floating, sinking or not moving, the droplets do not move that the solution immersed in the tissue after the concentration has not changed, the solution of the solute potential that is equal to the organization of the water potential.
Operation method
Experiments on the determination of water potential in plant tissues by the small fluid flow method
Materials and Instruments
Wheat Corn Kale Cotton Leaf Potato Tubers Beet Tubers Move I. Materials and equipment For more product details, please visit Aladdin Scientific website.
CaCl2 solution Methylene blue powder
Test tube racks Dissecting needles Finger test tubes Plugged graduated test tubes Pipettes Capillary burettes
Materials: wheat, corn, kale, cotton leaves or potato tubers, beet tubers per group: 7 pcs. of 10 ml finger test tubes, 7 pcs. of 10 ml stoppered graduated test tubes, 1 pc. of 5 ml pipette, 1 pc. of 10 ml pipette, 1 pc. of 1 ml pipette. 7 capillary burettes
Equipment: test tube rack, dissecting needle
Drugs: 1 M CaCl2 solution, methylene blue powder
II. Experimental steps
1. 14 test tubes into two rows, according to the required volume in one of the rows were added to 1 M CaCl2 solution, so that its dilution to 10 M l and the concentration range of 0.1 M -0.4 M, this group for the control group, and then respectively, with a pipette from the control tube to take 1 ml added to the other group of test tubes, (low concentration to the high concentration of the matching), this group is known as the test group.
2. Take 10 wheat plants, pick 1 piece of each allelopathic leaf of each wheat plant, each 5 pieces of head and tail stacked, take the middle part and cut it into 7 segments, each segment is 0.5 cm long, and put them into 7 test tubes of the test group respectively, (tuber roots are also acceptable), and shake the test tubes for 3-4 times within 30 minutes. 30 minutes later, use the dissecting needle to pick up the trace amount of methylenedioxymethylene blue powder, and put into the test tubes with shaking to make it dissolve completely and show blue color. dissolved and blue in color. A small amount of blue CaCl2 solution was sucked up with a capillary tube and gently inserted into the central part of the test tube corresponding to the control group, and a drop of blue solution was slowly dropped out, and it was carefully observed whether the drop was rising, falling or not moving. In a short period of time, the osmotic potential of this solution in which the blue droplet does not move or the average of the osmotic potentials of the two solutions (a slowly rising and an adjacent slowly falling solution) is the water potential of the plant tissue.
Third, the experimental results and calculations 
↑ means floating, ↓ means falling means not moving
Plant tissue water potential ψ = -iCRT
where ψ is the water potential, expressed as atmospheric pressure
R gas constant = 0.082 (at M -l/ M ol-k)
T absolute temperature (273 + t °C)
C concentration of solution in which the droplet is not moving
I van'tov correction factor ( CaCl2 i=2.6)