Biology - Osmosis

osmosis

the movement of water from a dilute solution to a more concentrated solution through a selectively permeable membrane

turgor

the state of a plant cell when it has gained enough water by osmosis for the cell membrane to push against the cell wall, making the cell firm

Plasmolysis

a plant cell that has lost water by osmosis and its membrane separates from the cell wall

what do plants use water for

-for support
-for transpiration
-for transport - as the water moves up through the plant it carries minerals
-As a raw material in photosynthesis

transpiration

the evaporation of water from mesophyll cells, followed by diffusion through the leaf air spaces and stomata

Potometer

measures the rate of water uptake by a cut shoot

weight potometer

measures the loss in mass of the pot plant

Factors affecting the rate of transpiration

Temperature, wind speed, humidity, light/darkness

Temperature

warmer conditions evaporate water faster

Wind speed

evaporation is faster in higher wind speeds as the wind rapidly removes the evaporating water away from the stomata and leaf surface, thus maintaining a steep gradient of moisture

Humidity

humid conditions restrict evaporation, as there is a decrease in moisture gradient between the leaf surface and the surrounding air

light/darkness

many plants close their stomata in darkness to reduce water loss