Questions- photosynthesis in higher plants Video Lecture - NEET

hello friends this video on
photosynthesis and higher plants part 24
is brought to you by exam feel calm no
more fear from exam and I think it is
question time now so we will discuss a
few questions now just to give you an
idea about whatever we have discussed so
far so let us say that question number
one it says by looking at a plant
externally can you tell whether the
plant is a c3 or a c4 why and how now as
I mentioned before there are quite a few
differences which can be instead between
a c3 and a c4 plant but not all of them
can be distinguished externally most of
the differences between a c3 and c4
plant is in their anatomy so if you
start study their leaf anatomy you will
be able to find out a lot of differences
but without considering the knife
anatomy you will have to look at the
behavior of the plant so the external
features of c-4 plants are they are
adapted to dry tropical regions so
plants which are able to survive in dry
regions they can be considered as c4
because they have high temperature
tolerance that is why they are able to
manage in dry regions they have greater
biomass productivity so the biomass
which you get out of these plants that
is quite large when compared was a pre
plan so that is another way of taking
whether it is a c3 or c4 but when you
are start studying their internal
structure then you get a lot of
differences like the arrangement the
multiple layers of metal sheet cells or
the compactness of c4 plants or the
larger number of chloroplasts and c4
plants so there are many differences
when you talk about their internal
structure but externally these are some
of the things which can tell you whether
it is a c3 or a c4 question of the -
even though a very few cells in a
seafood plant gang out of the
biosynthetic Kelvin pathway yet they are
highly productive
can you discuss why so now in this case
what happens is that even though not all
the sense that he
valyok Catholic pathway so only the it
is only the bundle sheath cells where
Calvin pack will stay in place but at
the same time if you see there are many
ways in which they are able to utilize
more out of it for example when you talk
about the process of photorespiration
that is in presence of light they lose
out some they they can lose out some of
their energy but that photorespiration
doesn't take place in a c4 plant so
photorespiration occurs in c3 but does
not occur in c4 plants but again for
photorespiration also you need some ATP
to be utilized so if photorespiration is
not happening so you are able to save
some ATP there so some savings you are
doing there and then when you talk about
the process of photosynthesis in case of
c3 times it takes place only when the
stomata is open but in case of c4 times
it can also take place when the stomata
is closed so that means also it is able
to produce some more ATP so they can
perform go to photosynthesis even when
stomata is closed so that is they are
able to produce more and that is why
they are more productive when compared
to c3 plants higher rate of carbon
assimilation in c4 plants back is also
it can assimilate more and more carbon
that is because in c4 plants the carbon
dioxide which enters into the calvin
cycle it comes from the hatch and slag
pathway so you can assimilate or add
more carbon so that it can continue the
calvin cycle even in absence of light
question number 3 Rubisco is an enzyme
that acts both as a carboxy ruiz and
oxygen ease why do you think Rubisco
carries out more carboxylation in c4
trunks now talking about Rubisco not
only rubus for any enzyme has got a
binding site or which is also known as
the active site or that substract
binding
now in case of Rubisco the active site
of Rubisco can bind to both oxygen as
well as carbon dioxide and that is why
it acts as both oxygen ease as well as
Kalibak series so when it binds to
carbon dioxide it acts as skyboxes when
it binds to oxygen it acts as oxygen is
now in case of now it depends on whether
know if carbon dioxide and oxygen both
are present in its vicinity it depends
on which is present in whole quantity so
the concentration of carbon dioxide is
more in fact less carbon dioxide will
bind to to disco and Rubisco will act as
a carboxyl if the concentration of
oxygen is more then oxygen will bind to
the Pisco and it will act as an oxygen
is now in case of c-4 plants if you see
the concentration of carboxyl carbon
dioxide is greater because in this
plants there is no photo respiration and
what happens in photorespiration it is
just the opposite of photosynthesis in
photosynthesis carbon dioxide is taken
in and oxygen is given out and in
photorespiration carbon dioxide is given
out and oxygen is taken in so if
although respiration is not happening
that means you are able to save some
carbon dioxide right because you are not
giving out carbon dioxide so the
concentration of carbon dioxide is
actually increasing because
photorespiration does not happen that
means the concentration of carbon
dioxide increases so since the relative
concentration of carbon dioxide is more
than oxygen therefore the troopers who
finds more carbon dioxide around and it
binds to carbon dioxide and access
carboxyl is in c4 plants question number
4 suppose there were plants that had a
high concentration of chlorophyll b but
lacked chlorophyll a would it carry out
photosynthesis now the question is flow
of the a is the main pigment responsible
for photosynthesis it is a necessary
pigment as i mentioned before also if
which is necessary is not there that
process will not think is so even though
it has a high concentration of
chlorophyll b but chlorophyll b is an
accessory pigment so it is just too good
to have pigment so even though you have
so much of it that is of no use if
chlorophyll a which is a necessary
pigment is not there
so therefore photos and pencils will not
take place if it lacks chlorophyll e so
it will not take place without profile a
so now the next question is then why do
plants have chlorophyll T and other
necessary pigments so now in
photosynthesis can take place without
necessary pigments then what is the
point of having them and I mentioned
before these accessory pigments have got
specific rules for themselves
my rule is they have to protect
blown-off is a from photo oxidation so
the basically ensures protection of
chlorophyll a because they know
chlorophyll a is necessary so they try
to protect chlorophyll in next second is
they have to occur some photosynthesis
in other regions of the spectrum because
when you talk about chlorophyll a
chlorophyll a absorbs light only in the
blue and the red regions that is my
maximum photosynthesis occurs in these
two regions but due to the presence of
these accessory pigments some small
amount of photosynthesis also take place
in the yellow region so that is because
of these and synthetic pigments so small
amount and axon to the effect so
similarly when light falls on these
pigments accessory pigments they also
absorb some wavelength and transfer that
energy to the main pigment that is
chlorophyll a now the last question for
this lesson why does the color of belief
kept in the dark
frequently yellow or pale green in color
which pigment do you think is more
stable okay
so in this case if you keep a leaf in
dark you do not expose it to lot of
sunlight so what do you think will
happen so when there is lot of fly
the pigment inside it will try to absorb
the red and the blue regions which
pigment will try to absorb that
chlorophyll a so in that case the green
will get reflected and that is why the
leaf will appear green but now the lift
that roof is kept in back so what is
happening it is appearing yellow or pale
green that is because now the
chlorophyll 8 is not active because
chlorophyll a is good at absorbing the
viewer and the red regions of the
spectrum but now not enough light is
there so it is not able to absorb the
blue and green blue and red regions
properly so chlorophyll becomes less
stable in absence of light therefore the
green color becomes lighter because
chlorophyll is not active and you flew
over it's not active it's not be able to
absorb the blue and red regions of them
with blue and red light of the visible
spectrum so which is more stable you
think right now the reef appears yellow
so that yellowish color mostly comes
because of the pigments on two things
because they are yellowish in color so
they generally absorb all other colors
and reflect the yellow balance and that
is why xanthophylls would be more stable
under such conditions so when the light
is in dark xanthophylls are more stable
when compared to clover so with this I
end this lesson and I hope that the
concepts of photosynthesis is clear to
you now if not please replay the videos
over and again so see you all in the
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