Cohesion and Adhesion
The attraction of water molecules to
other water molecules is called cohesion.
Cohesive forces are because
of the polar nature of the
water molecule.
The attraction of water molecules to molecules
of other substances is called adhesion.
water
mercury
Adhesive forces between the water and the walls of a test tube cause
water to form a concave meniscus.
In a thin capillary tube, the coloured water inches up the tube
because of cohesive and adhesive forces.
Root Pressure
Roots take in dissolved minerals from the soil
by active transport.
Water then enters the root through osmosis.
Root pressure plays a small part in the
movement of water through the xylem when
compared to transpiration pull.
From Root to Leaf: Water Transport in Plants
The evaporation of water through the stomata and lenticels in the
process of transpiration creates a tension or transpiration pull.
The Effect of Tonicity in Plant Cells
A hypertonic environment
has a high concentration of
solutes (e.g. sea water).
In a hypertonic environment,
water will move out of the
cell by osmosis.
Plant cells will undergo plasmolysis: the
cytoplasm shrinks away from the cell wall.
A hypotonic environment has
a low concentration of
solutes (e.g. distilled water).
In a hypotonic environment,
water will move into the cell
by osmosis.
Plant cells will become turgid: the cytoplasm
presses against the cell wall.
Turgid Elodea cells in a hypotonic environment.
Plasmolysis of Elodea cells in a hypertonic environment.
From Sink to Source: Sugar Transport in Plants
 read pages 315 – 321
 C3.4 Check and Reflect

page 322 #’s 1 – 5, 8