①Water is the main component of cell protoplasm

②Water directly participates in the metabolic process in plants

③Water is a good medium for various biochemical reactions and substance absorption and transportation

④Water can keep plants in their original posture

⑤ Cell division and extension growth require sufficient water.

①Water is a plant temperature regulator (water molecules have high vaporization heat and specific heat, which can lower body temperature through transpiration, making plants less susceptible to high temperature damage)

②The regulating effect of water on the microenvironment of plant survival (increasing atmospheric humidity, improving the temperature of soil and soil surface atmosphere)

Partial molar volume: refers to the effective volume occupied by 1 mol of the substance in the mixed system under the conditions of constant temperature, constant pressure and the concentration of other components.

2.3.1.1 Plasmolysis and plasmolysis recovery

2.3.2 Water potential composition of plant cells

2.3.1.3 Water movement between cells (water potential gradient)

Diffusion is the movement of material molecules (including gas molecules, water molecules, and solute molecules) from one point to another, that is, the random and progressive movement of molecules from a higher chemical potential area to a lower chemical potential area, which usually results in diffusion of molecules. Evenly distributed.

In the presence of a pressure difference, the collective movement of a large number of molecules in a liquid is called collective flow.

Shape indicators: Growth rate decreases wilting of young leaves Stems and leaves turn red in color

Physiological indicators: Leaf water potential Cell juice concentration or osmotic potential Stomatal condition

① The transpiration pull caused by the water potential gradient caused by water loss through transpiration is the main driving force for plants to passively absorb and transport water.

②Transpiration relies on the high heat of vaporization of water to reduce the temperature of plants and leaves, preventing them from being burned by high temperature and strong light.

③The updraft caused by transpiration helps the roots transport inorganic ions and organic matter absorbed from the soil and organic matter synthesized in the roots to various parts of the plant to meet the needs of life activities.

① Transpiration rate (TR): The amount of water lost by a plant through transpiration per unit leaf area in unit time is called the transpiration rate, also known as transpiration intensity. ②Transpiration efficiency: the mass of dry matter produced by the plant per kilogram of water consumed (g) ③Transpiration coefficient: The amount of water (g) consumed by plants to produce 1g of dry matter. It is the reciprocal of transpiration efficiency.

Stomatal transpiration (guard cells: kidney-shaped, dumbbell-shaped) (open during the day and closed at night)

overall transpiration

Internal factors: structural characteristics of stomata

Environmental factors: light, atmospheric humidity, atmospheric temperature, wind, soil conditions

① There are many root hairs in the root hair area, which increases the absorption area.

②The outside of the root hair cell wall is covered with pectin material, which makes it highly sticky and hydrophilic.

③The conductive tissue in the root hair area is well developed and has little resistance to the movement of water.

④The root hairs are long and slender and can enter the soil capillaries.

① Passive water absorption (the transpiration pulling force generated by transpiration is the driving force)

② Actively absorb water (relying on root pressure as power)

soil resistance

Root-soil interface resistance

Root radial and axial resistance

2.6.4.1 Root system factors

2.6.4.2 Soil conditions