Transcript transpirationx

Transpiration in Plants
STEP 2:
STEP 1:
Pressure Flow
Hypothesis
STEP 3:
STEP 4:
STEP 5:
Pressure Flow Hypothesis
Translocation
• Movement of
organic molecules
in plants
• What do you think
are some of these
molecules? Water,
sugar, carbon
dioxide, amino
acids, mRNA
Based on SINK AND
SOURCE dynamics
• Sink: the stored
sugar and water in
plant stems.
• Source: where you
get the nutrients
and water. Analogy:
Faucet
Leaves versus Stems:
• Which is the sink
and which is the
source ? Leaves are
the source, stem
are the sinks.
• How do you think
their roles change
with seasons? In
the winter, the stem
and the whole plant
acts as the source
to access stored
food.
STEP 2: Water from
xylem is transferred
to the phloem to
help break
down/dissolve food
in the phloem. The
water pressure is
kept at low.
STEP 3: Water is
being transferred
in the xylem
(going up) to
keep balanced
pressure.
STEP 4: water is
being transferred
from the phloem
– to maintain
pressure in the
phloem due to
excess water
from xylem from
step 2.
STEP 1: Food and water
enters phloem of the stem
through diffusion and
osmosis.
STEP 5: food is stored in the
sink cell.
Movement of water in plants
Process
Explanation/details
1. Water moves down concentration
gradients
Water moves through osmosis from an
area of higher to lower concentration.
2. Water lost by transpiration is replaced
by water from vessels
Water moves through osmosis from an
area of higher to lower concentration.
Water goes from a high water potential to
area of lower water potential. (analogy:
straw)
3. Vessel water column is maintained due
to cohesion and adhesion
Charges in water molecules and xylem
attract and repel each other to defy
gravity.
4. Tension occurs in the columns of water
in the xylem
A lot of water retained in xylem. Charges
in water molecules and xylem attract and
repel each other to defy gravity.
5. Water is pulled from the root cortex
into xylem cells
This is caused by capillary action – this is
when something is transport throughout
the system through concentration