Determination of water potential of plant tissue (small fluid flow method)

, experimental principle:In plant physiology, water potential is defined as the chemical potential (i.e. free energy) of water per molar volume, which is the basic measure of plant moisture energy status. Because the absolute value of water potential is not easy to measure, generally with the same temperature and atmospheric pressure of pure water as zero, other solutions compared with pure water and measured its relative water potential.
Plant
orientation
water potential determines the water exchange between it and the outside environment, if the water potential of plant tissue is lower than the permeability of the outer liquid (solute potential, i.e. the water potential of the solution), the tissue absorbs water so that the concentration of the outer liquid The proportion increases, on the other hand, if the water potential of the plant tissue is higher than the permeability of the outer liquid, that is, the water loss of the tissue makes the concentration of the outer liquid smaller and the proportion decreases, and if the two are equal, the water exchange remains dynamically balanced, and the concentration and gravity of the outer liquid remain unchanged.
Therefore, in order to determine the water potential of plant tissue, plant tissue can be placed in a series of incremental concentration solutions, if a certain concentration of solution is found before and after the plant tissue, the proportion of water between it and plant tissue can be considered to maintain a dynamic balance, the penetration potential of the solution is equal to the water potential of plant tissue. Because the concentration of the solution is known, its osmosis pressure can be calculated according to the formula, and its negative value is the permeability potential (ψπ) of the solution, representing the water potential (ψw) of the plant. ψw ψπ - P - CRTII, Materials,
Instruments
and
Reagents(i) Materials: Cabbage or Other Crop Leaves (ii) Instrument Equipment: 12 vials with pins, syringes with needles, tweezers, punchers, markers,
culture
dishes(iii) reagents: (1) sucrose series standard solution: said to take pre-dried at 60-80 degrees C sucrose 34.2g, dissolved in 70 ml distilled water,
capacity bottle
fixed capacity to 100 ml, to obtain 1mol/L standard sucrose solution. The 1mol/L standard sucrose solution was then diluted to 0.10mol/L, 0.20mol/L, 0.30mol/L, 0.40mol/L, 0.50mol/L, 0.60mol/L sucrose solution.(2) methene blue powder 3, experimental step (1) take
dry
clean penicillin bottles 9 for Group A, each bottle is added 0.10-0.60mol/L sucrose solution about 4 ml (About 2/3 of penicillin vials, another 6 dry and clean penicillin bottles for Group B, each bottle was added 0.10-0.60mol/L sucrose solution 4 ml and trace methene blue powder coloring, the above bottles with a marker pen indicated concentration.(2) take the functional blades of the sample to be tested, use a puncher to extract about 50 small discs, put in a petri dish, mixed evenly. With tweezers, 5-8 small fillets are clamped into penicillin bottles (group B) containing different concentrations of methylene blue sucrose solution. Cover with a bottle plug and immerse all the leaves in the solution. Place about 40min and shake the vial frequently to speed up moisture balance.(3) After a certain period of time, with the syringe needle to absorb a little bit of group B bottles of blue sugar, the needle inserted into the corresponding concentration of penicillin bottle solution in the middle, carefully release a small amount of fluid, observe the direction of the blue fluid flow (each determination is to be measured with the concentration of methylene blue sucrose solution to clean several injection needles).
this method to check the movement of fluid flow in each bottle. If the liquid flow rises, it indicates that the concentration of sucrose solution soaked in small fillets is reduced (i.e., the dehydration of plant tissue), which indicates that the water potential of the leaf tissue is higher than the permeability potential of the solution of the concentration, and if the blue liquid flow decreases, the water potential of the leaf tissue is lower than the permeability of the concentration; If the blue liquid flow is stationary, the water potential of the blade tissue is equal to the permeability potential of the solution of the concentration, and if it decreases in the solution of the previous concentration and rises in the solution of the 1st concentration, the water potential of the blade tissue is the average of the permeability potential of the two concentration solutions.4. ResultsCalculate the water potential of the blade tissue according to the following formula: ψw s ψπ s CRTi (MPa): ψw is the water potential (MPa) of the plant tissue; ψπ is the permeability potential (MPa) of the solution; R is the gas constant, 0.008 314L. Pa/(mol· K); T is the absolute temperature (273 plus t degrees C) K; i is the dissodiation coefficient (cane sugar s1, CaCl2 s 2.60)
5, note 1. The size and number of blades should be equal, otherwise it is easy to produce small fluid flow direction fluctuations in different concentrations of the results, so that it is impossible to determine the plant tissue water potential.。 2. The methene blue should not be added too much (the solution is slightly darker blue), otherwise the proportion of the solution in each tube of the experimental group will be increased.。 3. If the concentration range of the solution is not sufficient, several sucrose solutions can be incremented before and after this series