What is diffusion? Give one example.
Ans: The movement of molecules from higher concentration to lower concentration is called diffusion. Oxygen is utilized and carbon dioxide is removed during respiration in a leaf. This CO, collects in the intercellular spaces of the leaf Carbon dioxide diffuses from the intercellular spaces into the outer air. But oxygen diffuses in the reverse direction.
- What is Graham’s law of diffusion? Write its equation.
Ans: It states that the rates of diffusion of gases are inversely proportional to the square roots of their densities. Graham’s law is applied on the diffusion of gases.
1 d 2
- What are imbibition and imbibant?
Ans: The special type of diffusion in which an imbibant absorbs water
on its surface withcut dissolving in it is called imbibition. Imbibani is a hydrophilic surfaces like protein, starch or clay.
- Give two significance of imbibition.
Ans: Dry plant material like dry wood is placed in water. It swells and
its volume increases. Dry pea seeds are placed in water. These also swell. It helps in the g•.rmination of seed.
Differentiate between osmotic pressure and turgor pressure.
Ans: The maximum pressi re that develops when a solution is separated from its slIvent by a semi permeable membrane is called osmotic presi are. The pressure exerted by the cell sap on the cell wall of plant cell is called turgor pressure.
- What are water and solute potentials?
: The chemical potential of water is called water potential. The total kinetic energy of the molecules is called water potential. The decrease in water ‘potential due to dissolution of solute molecules or ions in water is called solute potential.
- Water is matric potential?
Ans: The decrease in the water potential due to affinity of water
molecules with the colloidal substances (protoplasm and cell wall) is called matric potential
- What is soil?
Ans: The complex composite mass made up of both inorganic and organic, components containing water and air is called soil.
- Give composition of soil.
Ans: Soil has followir 2 comlosition
- What is clayey soil? Give its advantage.
Ans: The soil consists mainly of clay particles are called clayey soils.
The clay particles are mostly of colloidal nature. They possess high water holding properties.
- Differentiate between soil texture and soil profile.
Ans: Relative proportion of the soil particles size is known as soil
texture. The arrangement of soil particles in layers is called soil profile.
- What is run away water? Give its significance for plant
Ans: Some of the water drains away along the slopes after a heavy rainfall or irrigation. This is called run-away water. It is not available to the plant.
- What is field capacity?
Ans: The amount of water retained by soil after the removal of excess water by gravitation is called the field capacity or the water holding capacity of the soil.
- What is hygroscopic water?
Ans: Water adsorbed on the surface of soil colloids is called hygroscopic water.
The water level at some depth from the soil where all pore spaces are filled with water is called wateretable.
- What is Wilting coefficient or permanent wilting point?
Ans: The amount of moisture left in the soil after a plant has
permanently wilt is called wilting coefficient.
- What is the significance of soil air for plant?
Ans: The soil particles are irregular in size and shape. Therefore,
interspaces are present between them. These interspaces are filled by air or partly by water. This soil air is essential for the proper growth of plant.
- What are Casparian strips? What is its significance?
Ans: The transverse and radial cell walls of endodermal cells have
Casparian strips. [hese strips are characteristics cell wall thickenings. These are imp-el:rifted with suberin. Subedit is impermeable to water. Therefore, the water with its dissolved substances cannot pass out of enoodermal cells.
- Differentiate between apoplast and symplast pathways.
Ans: The movement of x!, ater molecules through the adjacent cell walls is called apoplast pathway. The movement of water through the protoplast of the plant cells is called syinplast pathway.
- What is mycorrhiza? Give its significance for plant.
Ans: Mycorrhizae is an association of fungi and roots of higf:er plants.
Fungi increase the ability of absorption of water by roots.
- What is root pressure?
Ans: The hydrostatic pressure generated in the root which forces the water upward in the stem is called root pressure. Root pressure forces the water up from below.
- What is cohesion tension theory?
Ans: This theory states that the negative pressure or pull or suction is created in the leaves as a result of transpiration pulls the water upward.
- Differentiate between Absolute humidity and Relative humidity.
Ans: The amount of moisture actually present in the air is called its
absolute humidity. The percentage of the amount of moisture necessary for saturation at a particular temperature is called relative humidity.
- What is role of wind in transpiration.
Ans: Wind has a powerful effect on humidio . Dry wind removes the moist air from the i mmed kite vicinity of the plants. It lowers the amount of air moisture near plant. As a result, the humidity of the air is lowered. It promotes transpiration:,