Please Do Now: 1) What forces get water into the root
from the soil?
2) How does water get to the top of a tall building?
Agenda
 Do Now
 Data analysis
 Water transport and turgor pressure notes
 Review worksheet
Data Analysis Thursdays
 Data Analysis will work slightly differently today
 It will move fast (one chart)
 There will be no unifying question
Data Analysis: Chart 1
Species
Stomata density (#/mm square) Avg. yearly rainfall
(mm)
Spinach
20
135
Arugala
35
300
Red Maple
25
255
Ginko
45
350
1. What plant has the wettest environment?
2. What plant has the most stomata?
3. How does the yearly rainfall affect stomata density?
How does water move up to the
leaves from the roots?
 Two forces involved:
osmosis and cohesion
 Just like osmosis pulls
water in from the soil,
there is a gradient that
pulls it into the leaves from
the roots
 As molecules are pulled
into the leaves, other water
molecules are pulled into
the vasculature since they
are all linked together in a
chain of cohesion
The water molecules are linked
together until they evaporate,
pulling each other up the plant
How does water travel from the
roots to the leaves?
 It goes via the xylem,
which are tubes in the
stem of the plant
Plasmodesmata
 In plants, the cytoplasm
of the cells are not
separate
 They are connected by
plasmodesmata, little
tunnels between
different cells
 They help things move
faster throughout the
plant, including water
What happens when there is not
enough water?
 Wilting
 It is when there is not
enough water to
maintain turgor pressure
Death By Wilting
 When the water content
of the leaves drops too
low, the plasmodesmata
close down
 After this point, even if
they get more water
soon, the tissues will be
dead
What is turgor pressure?
 Turgor Pressure is the force that the expanded cell puts
on the cell wall
 It keeps the cell rigid (as opposed to flaccid)
What generates turgor pressure?
 When osmosis is pulling
water into the cell, the
cell gets larger
 This will continue until
the cell begins pushing
on the rigid cell wall
 At this point the
osmotic pressure pulling
molecules into the cell is
resisted by the cell wall
pushing back on it
Plasmolysis
 When there is not much water outside the cell, like when it is
dry out, osmosis will cause water to leave the cell
 This will take away turgor pressure, and the plant will wilt
(a.k.a. undergo plasmolysis)
 The cell membrane will shrink away from the cell wall, but the
plasmodesmata will stay intact as long as possible, if they
break the leaf is dead
What is Turgor Pressure?
 Osmosis is the flow of
water from high
concentration of H20
molecules to low
 If there are less solutes in
the water outside the cell
than inside of the cell this
will cause water to
continually flow in