Is the uptake and loss of water in plant cells due to changes in cell wall size?

The cell wall has changes, but its elasticity is worse than that of protoplasts, because it is composed of substances such as cellulose and pectin, so when there is a difference in the concentration of the inner and outer solutions, it does not change as much as the protoplast, so the plasma wall separation and recovery of the plasma wall is caused by the difference in the expansion and contraction ability of the two when they absorb water.

The cell wall of a plant cell is made up of cellulose and pectin. The inadequacy of water absorption and water loss in plant cells is due to changes in cell wall size. The main thing is the result of changes in the cytoplasm of the substance inside.

The cell wall is unchanging, and the cell wall is a bit like a framework of a plant cell. Dehydration absorbs only the inside. Plant cell walls are cellulose and pectin, which are less elastic but can also protect cells.

Water absorption and water loss in plant cells are caused by the difference in concentration between the inside and outside of the cell, which is the same as in animal cells.

Normal saline is commonly used in daily life to prevent cells from absorbing too much water and rupturing.

The cell wall is not elastic.

The cell wall of a plant cell is made up of cellulose and pectin. When plasma wall separation occurs in plant cells, the cell wall size and shape remain unchanged.

Water absorption and water loss in plants are due to the opening and closing of stomata on plant leaves, independent of changes in cell wall size.

There are also changes, but the changes are much smaller than the cell membranes, so there is separation

It is not a cell wall, it should be a cell membrane, and the size of the cell wall is generally constant.

The cell wall is unchanged and the cell membrane changes because it is the cytoplasm that changes.

This is because the concentration of the cell fluid inside the cell wall is different from the concentration outside.

Not necessarily, forPlant cellsIt doesn't have to be the same.

Ideally, the optic cell membrane.

It is a semi-permeable membrane, solvent molecules pass freely, solute molecules cannot pass through, ignoring the size of the molecule. then the amount of concentration of the substance.

Water molecules when equal.

The speed of entry and exit is equal.

But for plant cells, most of the bacterial cells, etc., there is a cell wall.

In the case of cells, due to the support of the cell wall, even the concentration of intracellular fluid is smaller than that of extracellular orange liquid.

concentration, nor can it continue to absorb water and rise. The osmotic pressure caused by the concentration difference at this time.

The force and the pressure of the cell wall are balanced, and the water molecules enter and exit at equal speeds.

At this time, the concentration of the inner and outer liquids is different.

The principle and conditions of water entering and exiting cells

The principles and conditions of water entering and exiting cells include the concept of osmosis, osmosis device, the conditions for osmosis to occur, the principle and the phenomenon analysis, etc., and the details of the principles and conditions of water entering and exiting cells are as follows

Permeation refers to the diffusion of water molecules (or other solvent molecules) through a semi-permeable membrane from a low-concentration solution to a high-concentration solution, which is a form of free diffusion.

Conditions under which osmosis occurs:

It has a semi-permeable membrane.

There is a concentration circle bond difference between the solutions on both sides of the semipermeable membrane.

A two-point analysis after the osmosis reaches equilibrium.

The magnitude of the concentration on both sides of the semi-permeable membrane: the concentration on the side with a high liquid level is still high.

The reason why the liquid level no longer rises: the concentration on side A is greater than the concentration on side B, the water absorption on side A will rise, the concentration will decrease, and when the osmotic pressure difference between A and B is equal to the pressure generated by the height difference between A and B hail ΔH, the liquid level remains stable.

Materials used to observe water absorption and water loss in plant cells: the outer skin of the onion, which is particularly dark in purple, a sucrose solution with a mass concentration of 0 3 g ml, and water.

Method steps: 1. Draw a small square on the outer surface of the onion scale leaf with a blade, tear off this small piece of onion skin with tweezers, on the outer skin of the onion, use the blade to cut some squares, and gently tear a small piece with tweezers (tear only the outer skin, don't tear it too thick, still leave it as a problem for students).

2. When taking the specimen, you can fold the inner epidermis of the onion outward and the outer epidermis inward, not too hard, and then take its outer epidermis as the material, put it flat in the water droplet of the glass slide**, and cover the coverslip.

1. Experimental preparation.

a) Ingredients: Thicker seedlings, radish strips or potato fries.

2) Supplies: beakers, test tubes, water, salt water.

Second, the method and steps.

1) Take two pieces of radish strips or potato fries, put them in a beaker filled with water and salt water respectively and soak them, and after a period of time, you can see that the radish strips in the clear water are stiff, and the radish strips in the salt water are soft. This suggests that plant cells can absorb or lose water, and that water absorption and water loss are related to the concentration of the solution in the environment. It should be noted that this experiment should be done before the class or given to the students during the previous lesson.

The experimental process takes about 20 minutes.

2) In this experiment, two plant seedlings can also be used, respectively, their roots are inserted in two test tubes filled with water and salt water (or sugar water), about 20min, two seedlings are taken out from the test tube for comparison, it can be seen that the seedlings in the clear water are stiff, and the seedlings in the salt water (or sugar water) are wilted. This also proves that plant cells can absorb water and can also lose it. At the same time, this experiment also illustrates the reason that excessive soil solution concentration or excessive fertilization affects the water absorption of roots.

3. Teaching suggestions.

The water absorption experiment of plant cells is not only a demonstration experiment in the section "Water Absorption by Roots" in the textbook, but also an introduction to this lesson. This experiment takes about 20 minutes. Therefore, students can be mobilized to carry out experiments with commonly used utensils before class, and then bring them to the class for demonstration.

During the presentation, a blank piece of paper should be added as a background behind the experimental material so that students can observe it clearly.

Only one copy was found.

Mature cells (with large vacuoles) of plants are generally selected for meristem cells (rectangular) or apical cells, and onion epidermal cells (with color and easy to observe) are generally selected, which are suitable for plasmo-wall isolation experiments.

Because the cell wall of a plant cell is very tough, it cannot continue to grow in size after absorbing water when it reaches its limit.

Determining whether a mature plant cell is losing water and absorbing water cannot be judged by observing the change in the volume of the cell for the following reasons:

Mature plant cells have been buried in membranous tightening and thickening, and are highly elastic and able to withstand large volume changes. Therefore, changes in cell volume do not immediately reflect changes in intracellular water.

Mature plant cells contain a lot of starch, which can absorb water and swell, which can play a role in regulating cell volume. Therefore, changes in cell volume do not fully reflect changes in intracellular water.

The water content in the cells of mature plants is in a steady state, with both osmotic pressure and sequential air permeability. Therefore, even if the cell volume changes, it does not necessarily reflect the change in the intracellular water of the fine bend.

In short, to determine whether the mature plant cells are losing water and absorbing water, it cannot be judged by observing the volume change of the cells, and qualitative and quantitative analysis methods should be used to detect the changes in intracellular water.

Because plants have cell walls, the cells will not be broken by water absorption, and the largest is the size of the cell wall, and the cytoplasmic content is surrounded by the cell wall.

Problem Solving Ideas: When there is a concentration difference between the inside and outside of the plant cell, the plant cell will absorb or lose water When the concentration of the external solution of the cell is greater than the concentration inside the cell, the cell loses water, and when the concentration of the solution outside the cell is less than the concentration inside the cell, the cell absorbs water Figure B Water flows to the outside of the cell, indicating that the concentration of the outside of the cell is large, 1) The leaves of the tree that have been low and wilted will gradually stretch and stiffen and be verdant At this time, the state of the plant cell is that the water in Figure B flows into the cell, indicating that the plant cell absorbs water; When the concentration of the surrounding aqueous solution is less than the concentration of the cell sap, the plant cells will absorb water, so the plant cells will absorb water and swell, and the wilted leaves will gradually stretch and stiffen

2) When you make a cold dish with salted cucumbers, a large amount of salty soup will gradually exude At this time, the cucumber cells are in a state where the water flows to the outside of the cell, indicating that the concentration outside the cells is large, and the plant cells lose water Therefore, after a period of time, a large amount of salty soup will appear in the plate

3) The principle of water absorption and water loss in plant cells is that the cell loses water when the concentration of the external solution of the cell is greater than the concentration of the cell fluid, and the cell absorbs water when the concentration of the external solution of the cell is less than the concentration of the cell fluid

So the answer is: (1)a; （2）b；(3) Greater than

Comments: Brother Dong:

Test points of this question: Water absorption and water loss of plant cells

Comments: For the knowledge of water absorption and water loss of plant cells, first, we must learn to recognize the map, and second, clarify the names and functions of each structure of plant cells, as well as the principles of water absorption and water loss of cells; The key to this question is to understand the principle of water absorption or water loss in plant cells, and to see which is the largest concentration of cell fluid or extracellular solution, and water always flows to the side with the highest concentration

The principle of water absorption and water loss in plant cells is osmosis; The principle of water absorption by root hair cells is osmosis, and the concentration of root hair cell fluid > soil solution.

Osmosis is the way in which mature plant cells with vacuoles absorb water, and the principle is that the protoplasm layer is selectively permeable, and there is a concentration difference between the solution inside and outside the protopplasm layer, and water molecules can diffuse from the side with low solution concentration through the protoplasm layer to the side with high solution concentration.

The osmotic pressure of the solution is related to the amount of solute molecules in the solution, the more the amount of solute molecules in the solution, the higher the osmotic pressure, and vice versa.

When comparing the osmotic pressure of the two solutions, the amount of solute molecules in the two solutions is used as the standard for comparison. If the solute molecules are the same, the mass fraction can also be compared. The cell that is able to absorb water through osmosis must be a living cell.

After the plant cells absorb water, the volume of the canopy increases, at which point its s.

a.Enlarge. b.Minish.

c.No change.

d.is equal to zero.

Correct answer: The state seepage increases.