Water in plant tissues exists in two different states; bound water that is tightly bound to the protoplasmic colloids, and free water that is not tightly bound to the protoplasmic colloids but is free to move.

Operation method

Experiments for the determination of free water content in plant tissues

Principle

When the plant tissues were in contact with the highly concentrated sugar solution, the bound water remained in the tissues because it was adsorbed by the protoplasmic colloidal particles; the free water was extravasated into the sugar solution along the water potential gradient because it was not adsorbed by the protoplasmic colloidal particles, so that the concentration of the sugar solution was reduced. After the tissues were immersed in the sugar solution for a certain time, the free water content in the tissues could be calculated based on the decrease in the concentration of the sugar solution, while the bound water content could be calculated by drying the plant tissues to find the total water content and then subtracting the free water content.

Materials and Instruments

Potato
Sucrose solution
Weighing flasks; Perforators; Abbe Refractometers; Hand-held Sugar Meters; Electronic Analytical Balances; Rapid Moisture Analyzers; Constant Temperature Ovens

Move

1. Take 3 weighing flasks (three repetitions), number them sequentially and weigh them individually.

2 . Select several plants with consistent growth, and take several pieces of representative leaves with consistent parts, growth, and leaf age, and drill round pieces with a 0.5cm diameter perforator (pay attention to avoid thick leaf veins), randomly fill each bottle with 50 pieces, immediately add the cap, and weigh the fresh weight of the sample being tested.

If the plant under test is tuber (potato), first drill round strips with a perforator, and then cut them into round slices of about 1㎜ thickness, and weigh 1~2 g of round slices for each treatment (according to the actual weighing record).

3. Quickly add about 5 ml of 60-65% sucrose solution to each bottle (be careful to shake well and not to let the discs overlap), and weigh each bottle of sugar solution.

4. Place the bottles in a dark place for 4-6 h (if plant tubers such as potatoes are used for the experiment then treat them for about 1 h without placing them in a dark place), during which time they are shaken gently and frequently.

5. After a predetermined time, shake the sugar solution well. Then use a hand-held sugar meter or Abbe refractometer (see appendix for the use of methods) to determine the concentration of each bottle of sugar solution (%) and the original concentration of sugar solution (%). The measured sugar concentrations were corrected according to Table 1 or Table 2, and then the free water content of plant tissues was calculated according to equation (2).

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