High school biology The absorption of water by plants

Question 1: First of all, you need to understand the function of using absorbent paper to suction, using absorbent paper to attract is not to absorb the water added dropwise, but to let the water dripping from one side to the other side, so as to soak the entire onion epidermal cells. (You said that after sucking, the sucrose is still there, yes, but because the dropwise water is added to it, its concentration is also reduced.)

When the concentration of the external solution is reduced, the plasma-wall separation and restoration can occur. ）

The principle of two operations: when the concentration of the external sucrose solution is the concentration of the cell fluid, the water molecules in the cell will diffuse from the low concentration environment in the cell to the high concentration outside, and the plasma wall separation will occur. When the cells that have undergone plasma wall separation are soaked in clean water, the water molecules will diffuse to the high concentration of cell fluid and the plasma wall will be separated and restored.

Problem 2: Immature plant cells are relatively small in size, and have not yet formed "**vacuoles" or only small vacuoles. These cells do not necessarily fail to osmosis, but only because there are no vacuoles or vacuoles are too small, so the amount of osmosis is relatively small, and their main way of water absorption is mainly based on the hydrophilic substances contained in it to absorb water by "swelling".

1.The cell wall is fully permeable, so water can pass through the cell wall without hindrance! When the cell wall is separated, the concentration of the cell fluid is quite large, which means that the cell has a strong ability to absorb water at this time, so when the water passes through the cell wall, it will be absorbed by the cell immediately.

This is why the use of absorbent paper to absorb water can only suck out the water outside the cell, of course, it can only be absorbed after the cell is in contact with water or solution for a while, otherwise the effect is not obvious) This leads to the dilution of the cell fluid concentration and the restoration of the plasma wall.

2.Just the 1stThe cell fluid referred to in it can be roughly regarded as the solution in the vacuole in the plant cell.

The main condition for osmotic water absorption is that the concentration of the cell fluid is greater than the concentration of the extracellular solution. Therefore, only in plant cells with large vacuoles can it have the ability to penetrate and absorb water. The concentration difference between the small vacuolar cells and the outside world is not very obvious, so generally the small vacuolar cells such as dried seeds absorb water by swelling!

Understand what is a solution, absorbent paper, that is usually called, here he sucks a solution, do you think, usually a rag, you just rub water.

After the cabbage leaves are placed vertically into different pigment solutions, the color spots of the corresponding pigments gradually appear in the cabbage leaves over time, and after standing for 24 hours, the color of the cabbage leaves becomes pigment color. It turns out that the roots and leaves of the plant contain tiny ducts. Under the pull of transpiration, plants transport water from the soil to the rhizomes and leaves through these ducts.

The leaf stomata will have water vapor escaping due to heat, that is, transpiration, due to the continuous loss of water in the leaves, the concentration increases, and due to the osmotic pressure, the water is forced to move from the low place of low concentration to the high place of high concentration; In this way, the root water moves towards the leaves, and the concentration increases, and in the same way, the water penetrates into the roots of the plant and moves towards the leaves.

Because 1) photosynthesis.

2) As a transport carrier.

3) Transpiration.

4) Maintain the physiological level of cells.

There are a few reasons why plants absorb water.

1, the plasmo-wall separation cannot be observed.

phenomenon, add sucrose.

The solution cells remain in their original state.

2. Suppose there is no cell wall.

After adding sucrose solution, the cells will lose water and shrink, and then add water to gradually relax and return to the original size.

3.No, because the cell wall of the plant restricts the expansion of the cell.

4 drops with sucrose solution, the location of the protoplasmic layer (separated from the cell wall?) Inward contraction?

Add water, the position of the protoplasm layer (swelling outward?) ）

1. The main organ of green plants to absorb water is the root; The main site of water absorption in green plants is the epidermal cells in the mature area of the root tip.

2. The following two conditions must be met for the generation of osmosis:

a Has a semi-permeable membrane.

b. The solution on both sides of the semipermeable membrane has a concentration difference.

3. The way plants absorb water:

Swelling and water absorption: a. Characteristics of cell structure: no large vacuoles are formed in the cytoplasm.

B. Principle: refers to the main way of water absorption before the formation of large vacuoles in the cell, and there are a large number of hydrophilic substances in the cell wall and cytoplasm of plants - cellulose, starch, protein, etc., which can absorb a large amount of water from the outside.

c. Examples: Cells and dried seeds in the apical meristem.

Osmotic water absorption: a. Characteristics of cell structure: there is a large vacuole in the cytoplasm, the cell wall is fully permeable, the protoplasmic layer is selectively permeable, and the cell fluid has a certain concentration.

b. Principle: Internal factors: the elasticity of the cell wall is smaller than that of the protoplasm layer.

External factors (concentration difference between the two sides): external solution concentration, cell fluid concentration, cell water absorption, external solution concentration, cell fluid concentration, cell water loss;

c. Verification: plasma wall separation and plasma wall separation and restoration;

d. Example: epidermal cells in mature areas, etc.

4. The trend of water flow:

The water goes to the high (where the concentration of the solution is high). The water density is small, the water potential is low (the concentration of the solution is large); The water density is high and the water potential is high (the concentration of the solution is low).

5 Pathways for water to enter the inside of the root tip:

1) Layers of cell ducts inside the epidermal cells in the mature zone.

2) Cell walls and intercellular ducts of cells in various layers of cells inside the epidermal cells of the mature zone.

6. Utilization and loss of water

a. Utilization: 1% 5 of water participates in life activities such as photosynthesis and respiration.

b. Loss: 95% 99% water is used for transpiration. The significance of water loss by plants through transpiration is the main driving force for plants to absorb water and promote water transport in the body.

7. The cell that can undergo plasmo-wall separation should be a permetic system, which is a phenomenon that only occurs in a high concentration of external solution in a living plant cell (mature plant cell) with large vacuoles. (The cells of the human body, it does not have a cell wall, so there is no plasma-wall separation.) The maize apical cells did not form large vacuoles, and the cells in the apical meristem and elongation zone of maize, cambium cells and dry seed cells did not have large vacuoles, and they mainly absorbed water by swelling and did not have plasmo-wall separation.

Onion epidermal cells and root hair cells are two types of mature plant fine. ）

The process by which plants absorb water.

Depends on the swelling effect of root hair cells.

The protoplasmic layer includes the cell membrane, the vacuolar membrane and the protoplasm in between

The protoplasmic layer is 2 membranes. The cell wall is fully permeable and the protoplasmic layer of the dead cell is fully permeable.

Cytofluid refers to the fluid inside the vacuole.

1 Plasma wall separation: Internal factors: The elasticity of the cell wall is less than that of the protoplasm layer.

Extrinsic causes: The concentration of the external solution is greater than the concentration of the cell fluid.

2 Plasma wall separation refers to the separation of the protoplasmic layer from the cell wall

3.When plasmo-wall separation occurs, the vacuole becomes smaller, the color of the vacuole becomes darker, the cell fluid concentration increases, and the size of the cell remains basically the same

Plants absorb nutrients mainly through roots and leaves.

Roots absorb water mainly through osmosis in the root hair area, as well as metal ions through active transport (which requires energy consumption).

Leaves are mainly photosynthesized by chloroplasts to synthesize carbohydrates (mainly starch), and respiration through mitochondria to produce energy substances ATP

Individual plants have heterotrophic structures that assist in absorption, such as Venus flytraps and Nepenthes, which can secrete chemicals to break down insects and then absorb them.

Trust me, my homework is the same as yours, I just learned from someone else.

It relies on the absorption of root hairs and is the result of transpiration pull.

Because water is a factor that affects the metabolism of cells.

Generally speaking, water is free water in cells, the more free water, the more vigorous the cell metabolism, and one of the most important indicators of metabolism is respiration. Therefore, the amount of water affects the strength of the respiration of the plant (water is also a reactant of respiration).

The main organ of the plant to absorb water and inorganic salts is the root The main part of the root to absorb water is the mature area of the root tip, and the mature area has a large number of root hairs, which greatly increases the area of contact between the root and the water in the soil, which is conducive to water absorption, and the root tip mature area and a part of the cells inside the upper root differentiate to form a duct, which can transport water and inorganic salts

So the answer is: roots; mature area; Hair; Surface area