Phloem Transport Video Lecture | Biology for JAMB

phloem transport flow from souls to sink
sucrose is transported by the vascular
tissue phloem from souls to a sink souls
is a part of blonde which synthesizes
food leaf sing the part that needs us
those food souls and sink may reverse
depending on the season
sugar stowed in the roots may be
mobilized to become a source of food in
the early spring when the butts of trees
act as sink they need energy for growth
and development of the photosynthesis
operators since the souls sink relation
is variable the direction of the
movement of phloem can be upwards or
downwards that is bi-directional food in
phloem SAP can be transported in any
required direction so long as there is
source of sugar and a sink able to stow
or remove the sugar phloem sap is mainly
water and sucrose but other sugars
Hartman's and amino acids are also
transported or translocated through
phloem pressure flow or mass flow
hypothesis translocation is a phenomenon
of conduction of organic or inorganic
solutes from one place to another the
mechanism of transport through phloem is
not perfectly understood and the
principle theories are the mass flow
hypothesis the most accepted mechanism
for translocation of sugars from source
to sink is called pressure flow
hypothesis the German physiologist munch
in 1930 formulated this hypothesis this
can be demonstrated by simple experiment
to Osmo meters
a-and be joined by horizontal tube
forming a closed system the Osmo meter a
has a membrane enclosing v these are
immersed in two tubes connected by a
glass tube water enters both the Osmo
meters but more water enters into a then
B due to higher concentrated solution
existing create greatest suction force
but as turgor pressure increases in Osmo
meter a water will move through
horizontal tube X into Osmo meter B
since the membrane is permeable only to
water water will be pressed out of be so
circulation of blood takes place from
the tube in which B is present into the
tube in which a is present through the
connecting tube Y a continuous mass
movement will take place under the
osmotic concentrations in both a and B
are equalized if there is a continuous
supply of solute to a and a continuous
removal of solute from the receiving
Osmo meter B there will be a continuous
pressure flow from A to B thus pressure
flow continues when one of the cells is
a supplying cell and the other is a
receiving cell comparison of the model
the cells of leaf are considered to be
the supplying units comparable to
osmotic cell a and the cells of root
constitute the receiving organs
comparable to osmotic cell B the xylem
is comparable to the both containing
water for both the osmotic systems the
sieve tubes of phloem correspond to
glass tube X