Question

Short / Long answer type questions.
Write short notes on
(a) Diffusion pressure deficit, (b) Plasmolysis, (C) Water holding capacity, (d) Root pressure, (e) Water potential, (f) Guttation, (g) Osmosis, (h) Diffusion pressure, (i) Turgor pressure, (j) Capillary water, (k) Diffusion.

Answer 1

A. DPD: Diffusion pressure deficit is the difference in the diffusion pressure of the solute and the pure solvent when both are subjected to the same atmospheric pressures. To remove this deficit, the solution would absorb more solvent molecules. Water moves from low DPD to high DPD.

B. Plasmolysis: It is the withdrawal of protoplast of a plant cell from its wall due to excessive loss of water from cell due to the exosmosis. It occurs when a cell is placed in a hypertonic solution.

C. Water holding capacity: The total amount of water a soil can hold at its field capacity. Sandy soils tend to have low water holding capacity.

D. Root pressure: The pressure exerted inside the xylem channels of the root that helps in the upward movement of the water.

E. Water potential: Refer to the free energy of water which helps in the movement of water between any two systems. It is measured in pascals (Pa). Water potential of pure water at standard temperature and pressure is taken to be zero. As the solute particles are added to the water, the water potential starts lowering.

F. Guttation: It refers to the exudation of the xylem sap from the margins of the leaves through specialized pores called hydathodes. Guttation is particularly seen in grasses.

G. Osmosis: The passage of solvent molecules from a region of their higher concentration to a region of their lower concentration through a semi-permeable membrane. It occurs spontaneously due to the pressure gradient.

H: Diffusion pressure: The pressure exerted by molecules or ions during their diffusion process (from high concentration to lower concentration)

I. Turgor pressure: When a cell is placed in hypotonic solution, water diffuses into the cell causing the cytoplasm to build up pressure against the wall of the cell. This pressure is called turgor pressure. It causes rigidity in the cells.

J. Capillary water: The water that remains in the soil after gravitational water is drained out, that is subjected to laws of capillary movement.

K. Diffusion: The movement of molecules or ions from a region of their higher concentration to a region of their lower concentration, until the molecules are evenly distributed throughout.