Transport in plants: Phloem; translocation - Life Processes, Science, Class 10 Video Lecture

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let us now look at the process of
translocation what is translocation it
is the movement of food from leaves to
different parts of the plant let us
quickly look at the flowing tissues
phloem are generally living cells except
the phloem fibers so this is also made
up of several elements let us quickly
have a look at the phloem elements they
have sieve tubes these these tubes are
Abuna cells with perforated cell walls
so if you see their cell walls have
perforations and these perforations and
the plate is known as the sieve plates
these perforations are basically known
as the sieve that is why they are called
sieve tubes the sieve tubes are
accompanied by the companion cells the
word companion means a friend somebody
who accompanies so these companion cells
actually accompanies the sieve tubes
what will they do
they regulates the metabolic activities
of the sieve tube elements so here you
can see this is the sieve tube this is
the sieve plate with perforations and
these are the companion cells so the
companion cells are kind of supporting
them sieve tubes
now these sieve tubes along with the
companion cells are mainly used for
conduction so the sieve tubes along with
the companion cells are used for
conduction so other than this they also
have phloem Carol parenchyma which is
mainly used to support the sieve tubes
and also store food for the for example
xylem parenchyma was also mainly used
for storage similarly this flowing
parenchyma is also used primarily for
storage then we have flowing fibers
which are again dead cells and they are
only to give mechanical strength to the
plants so what did we see that in xylem
it was the track heads and vessels which
were actually used for conduction
similarly in case of phloem it is the
sieve tubes along with the
in cents which is used for
transportation so what oil does a flow
in conducts a flow in conducts the food
which is which is prepared during
photosynthesis and stored in leaves it
also conducts some other important
substances like hormones and minor acids
which are needed by the plants so
product the photosynthesis that is
starch or glucose is transferred into
flowing tissue using energy from ATP now
osmotic pressure of the flowing tissue
increases so now we are seeing what
actually causes this translocation to
take place like how we saw in case of
ascent of ZAP it occurred because of the
processes diffusion osmosis and
transpiration similar is why this
translocation occur what causes it to
occur now the product of photosynthesis
is passed into the phloem tissue using
the energy from ATP right that is the
adenosine triphosphate molecules now
once the transfer is done so what
happens to the phloem tissue the osmotic
pressure of the phloem tissue increases
now when there is a difference in
pressure the phenomenon of osmosis will
take place that as materials will start
moving from the phloem tissue which is
at higher osmotic pressure to other
tissues which are at lower osmotic
pressure and this actually leads to this
process of translocation so
translocation is mainly governed by the
change in osmotic pressure due to the
transfer of the product of
photosynthesis into the phloem tissue
loss Multi pressure of the phloem tissue
increases therefore the material start
moving from higher osmotic pressure of
flow increased to the lower optimistic
pressure of the other tissues so let us
quickly distinguish between xylem and
phloem in xylem we have unidirectional
transport that is the transport is only
in one direction that is from downwards
to upwards but in phloem it is
bi-directional transport because from
leaves it has to come to the lower
branches as well as to the upper
branches so it has to go everywhere
basically
xylem transports water and minerals from
roots to the aerial plant parts whereas
phloem
and sports food and nutrients from
leaves to different products facts xylem
are mostly dead cells at maturity phloem
are mostly living tissues except the
phloem fibers xylem occurs at the center
of the vascular bundles whereas phloem
occurs on the outer side of the vascular
bundle so you can see here this is how a
vascular bundle actually looks look like
this is the cross-section of a vascular
bundle so if you see these are the xylem
x' these are the layers of xylem and the
outer layers are the layers of the soil
so the xylem lies towards the center and
the phloem lies towards the outer side
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