DEFINITIONS AND KEY- POINTS FOR OBJECTIVES OF DIFFUSION, OSMOSIS, ABSORPTION

TERMS .. .
DEFINITIONS
Diffusion The  movement     of    molecules   from   higher

concentrationto     lowerconcentrationis   called

Chemical

potential       .

The total kinetic energy of the molecules is called chemical potential.•
Graham’s law It  states       thatthe   rates            of diffusionof gases     ai.

inverselyproportional to the square roots of the .r
densities.

Diffusion pressure The pressure exerted by the diffusing particles is known as diffusion pressure.
Imbibition The special type of diffusion in which an imbibant absorbs water on its surface without dissolving in it is called imbibition.
Imbibition pressure The   force  generatedby  theimbibantsis  called

imbibition pressure or metric potential.

Osmosis The movement of solvent molecules front the regiQn
  of higher concentration          to         the          region  of lower

concentration through semi permeable membrane is called osmosis.

Osmotic pressure The     maximum        pressure          that          develops          when    a

solution          is separated from        its solvent by a semi
permeable membrane is called osmotic pressure.

Water potential The chemical  potential          of water           is called water

potential. The total kinetic energy of the molecules is called water potential.

Solute potential :-. The decrease in water potential due to dissolution of

solute molecules or ions in water is called solute

.         .

Matric potential The decrease in the water potential due to affinity of

water molecules with the colloidal substances (protoplasm and cell wall) is called matric potential.

Pressure potential The turcor pressure (TP) exerted by the vacuole is called pressure potential.
Soil [he complex composite mass made up of both inorganic and organic. components containing water and air is called soil.
Soil texture Relative          proportion        of the   soil          particles           size      is

known as soil texture.

Run away water Some of the water drains away along the slopes

after a            lieu\ v   rainfall. or         irrigation.          This      is          called

run-a um u ater.

Field capacity of soil .1-he  amount            of 11 at e r       retained          by        soil       after     the


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removal of excess water by gravitation is called ths. field capacity or the water holding capacity of the soil.

Ilygroscopic water_ . Water adsorbed on the surface of soil colloids is called hygroscopic water.
Capillary water The ‘sater which fills the spaces between the non

colloidal          smallersoil       particles           is          called   capillary
water.

Water table The water level at some depth from the soil where all pore spaces are filled with water is called Water table.
Wilting coefficient The amount. of moisture left in the soil after a plant has permanently wilt is called wilting coefficient.
Apoplast pathway The movement of water molecules through the adjacent cell walls is called apoplast pathway.
Symplast pathway The movement of water through the protoplast of the plant cells is called symplast pathway.
Root pressure The hydrostatic pressure generated in the root which forces the water upward in the stem is called root pressure.
Capillary tube A glass tube with a narrow bore is called a capillary tube.
Cohesion tension theory 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.
Adhesion The attraction between the water molecules and the cell wall of the xylem cells is called adhesion.
Transpiration The evaporation of water from the aerial part of plant is called transpiration.
Saturation deficit Saturation      deficit   is          the       difference          between          the

amount of water vapour actually present in the air and the amount necessary to completely saturate it.

Absolute humidity The amount of moisture actually present in the air is called its absolute humidity
Relative humidity The percentage of the amount of moisture necessary for saturation at a particular temperature is called relative humidity.

 

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