2. Diffusion
▪ Net movement of molecules from a region of high
concentration to low concentration
▪ Rate of diffusion of gases is faster than liquids or
solids
3. Diffusion
▪ The pressure exerted by the diffusing particle is
known as diffusion pressure
▪ Rate of diffusion depends on
1. Diffusion pressure gradient
2. Temperature
3. Density of diffusing particle
4. Medium through which diffusion occurs
▪ Examples of diffusion in plants
1. Transpiration
2. Photosynthesis
3. Respiration
4. Passive salt uptake
4. Osmosis
▪ Diffusion of solvent molecules from a region of low
solute concentration to high solute concentration
through a semipermeable membrane
5. Osmosis
▪ Separation of two solutions or a solution and its
solvent generates pressure due to presence of
dissolved solutes i.e osmotic pressure
▪ ∏= iCRT
▪ Osmotic pressure is a colligative property
7. Significance of osmosis
1. Cell to cell movement of water
2. Opening and closing of stomata due to
osmotic entry of water which regulates
guard cell turgidity
3. The phenomena helps to maintain cell
shape
4. Turgidity of the cells in young seedlings
allows them to come out of the soil
8. Plasmolysis
It is the phenomena by which plant cell loose
water when placed in a hypertonic solution
