Leaf (Structure and Functions) - CBSE Class 6 Science Video Lecture

good morning children today we shall
learn about the leaves its functions and
the modifications if you look around you
would find many kinds of leaves some
leaves are small
for example the acacia leaves and some
leaves are big for example the banana
leaf not just the size even the shapes
are different like the long and thin
leaf in the grass needle-like shape in
the pine circular shape in the waterlily
etc some leaves have smooth edges like
in the banana and others such as in the
oak have jagged edges so there are many
varieties of leaves but the basic
structure of all the leaves is the same
a leaf rises from the node of the stem
the part of the leaf which is attached
to the stem is the petiole each leaf has
a broad flat surface which is generally
green in color it is called the leaf
blade or the lemon ax look carefully you
would find patterns of line on the lemon
ah
these lines on the lamina of the leaf
are called the veins observe carefully
there is a thickest Twain in the middle
of the leaf it is called the midrib the
veins act as a pipeline which carries
the water minerals and the food up and
down the leaf
you know one can tell what kind of a
root a plant has by just looking at the
leaf surprised let us see the veins in
the plant with the fibrous roots are
parallel to each other on the both the
sides of the midrib like here we see on
the banana leaf the arrangement of veins
on a leaf is called the leaf venation
and when the veins on the either side of
the midrib are parallel to each other we
call it parallel venation like here in
the case of banana leaf
in the plants with the tap root system
the veins former net-like design on the
both sides of the midrib this type of a
nation is called the reticulate venation
for example the hibiscus leaf has the
reticulate venation so we can say the
hibiscus has a tap root system what are
the functions of a leaf let us see we
all know that the main function of leaf
is to make food hence it is called the
kitchen of the plant the leaves are
green because they have a green pigment
called the chlorophyll the chlorophyll
traps the sunlight and the plant
produces the food which is glucose using
carbon dioxide water and the trapped
energy of the sunlight this process of
making the food which is glucose is
called photosynthesis
you know the photosynthesis is the main
source of oxygen on the earth
besides making food the leaves perform
some other tasks too
the leaves are full of tiny openings
which are called stomata the stomata are
used to exchange gases with the
environment like absorbing the carbon
dioxide and releasing the oxygen gas the
plants also release water vapor by the
transpiration process through the
stomata the transpiration helps the
plants to cool down there is another
advantage of transpiration you know when
the leaves lose water during the
transpiration the roots absorb the water
to make up for it and the minerals comes
into the plants along with the water
this upward pole for the transportation
of water and the minerals along with it
is caused by the transpiration process
the transpiration also helps in the
water cycle of the nature by increasing
humidity in the nature which causes the
rain later
apart from these tasks in some plants
the leaves perform some special tasks
let us see what they are in certain
plants such as cabbage spinach lettuce
etc the leaves store the food
in certain plants like the P Grapes etc
the leaf turns into thread like tendrils
the plant's coiled a tendril which is
the modified leaf around a support to
climb on it
the cactus plant grows in the desert the
leaf of the cactus plant are reduced to
spines so that the plant doesn't lose
water during their transpiration the
spines also protect the plant from
grazing animals now the question is who
makes the food well it's the green
fleshy stem which makes the food in the
case of cactus plant the needle-like
leaf modification is seen in the plants
like the pines fir spruce etc the leaves
are the needles of these trees are kept
all the year long
these leaves do not freeze in the ice
cold winters and can manufacture food
even in the winter without losing much
water
you know they are certain plants which
eat insects and they are called
insectivorous plants for example the
Venus flytrap
pitcher plant etc here
the leaves are modified to set the trap
for insects in case of the Venus flytrap
the lamina of the leaf is divided into
two parts with join at the midrib the
midrib acts like a hinge so when the
insect sits on the leaf the two parts of
the lamina fold at the midrib and come
together to trap the insect
the pitcher plant is another
insectivorous plant and the leaves in
the case of pitcher plant are modified
to form tube-like structures with hair
and this is used to trap insects so to
sum up what we learn today the functions
of leaves are to prepare the food to
exchange gases through the stomata and
to keep the plants cool by the
transpiration process
the leaves are also modified to perform
special tasks to store food for example
in the case of cabbage tendrils to climb
up the support for example in case of
peas the leaves arm also modified into
spines to reduce water loss in the case
of cactus
the needle-like leaves in the case of
pine to not freeze in the cold and
lastly the modified leaves trap insects
in the case of Venus flytrap so that was
all about the amazing leaves bye bye
children