.The most impotant function of the trichomes is:
(1) They prevent water loss due to transpiration
(2) They prevent herbivory
(3) They are sensory structures that decipher the wind velocity and direction
(4) They play an important part in pollination of plants
.
.
Answer ▽ ✅Verified
(1) They prevent water loss due to transpiration
Epidermal Tissue System
The epidermal tissue system forms the outer-most covering of the whole
plant body and comprises epidermal cells, stomata and the epidermal
appendages – the trichomes and hairs. The epidermis is the outermost
layer of the primary plant body. It is made up of elongated, compactly
arranged cells, which form a continuous layer. Epidermis is usually single layered.
Epidermal cells are parenchymatous with a small amount of
cytoplasm lining the cell wall and a large vacuole. The outside of the
epidermis is often covered with a waxy thick layer called the cuticle which
prevents the loss of water. Cuticle is absent in roots. Stomata are structures
present in the epidermis of leaves. Stomata regulate the process of
transpiration and gaseous exchange. Each stoma is composed of two bean shaped
cells known as guard cells which enclose stomatal pore. In grasses,
the guard cells are dumb-bell shaped. The outer walls of guard cells (away
from the stomatal pore) are thin and the inner walls (towards the stomatal
pore) are highly thickened. The guard cells possess chloroplasts and
regulate the opening and closing of stomata. Sometimes, a few epidermal
cells, in the vicinity of the guard cells become specialised in their shape and
size and are known as subsidiary cells. The stomatal aperture, guard
cells and the surrounding subsidiary cells are together called stomatal
apparatus. The cells of epidermis bear a number of hairs. The root hairs are
unicellular elongations of the epidermal cells and help absorb water and
minerals from the soil. On the stem the epidermal hairs are called
trichomes. The trichomes in the shoot system are usually multicellular.
They may be branched or unbranched and soft or stiff. They may even
be secretory. The trichomes help in preventing water loss due to
transpiration.
plant body and comprises epidermal cells, stomata and the epidermal
appendages – the trichomes and hairs. The epidermis is the outermost
layer of the primary plant body. It is made up of elongated, compactly
arranged cells, which form a continuous layer. Epidermis is usually single layered.
Epidermal cells are parenchymatous with a small amount of
cytoplasm lining the cell wall and a large vacuole. The outside of the
epidermis is often covered with a waxy thick layer called the cuticle which
prevents the loss of water. Cuticle is absent in roots. Stomata are structures
present in the epidermis of leaves. Stomata regulate the process of
transpiration and gaseous exchange. Each stoma is composed of two bean shaped
cells known as guard cells which enclose stomatal pore. In grasses,
the guard cells are dumb-bell shaped. The outer walls of guard cells (away
from the stomatal pore) are thin and the inner walls (towards the stomatal
pore) are highly thickened. The guard cells possess chloroplasts and
regulate the opening and closing of stomata. Sometimes, a few epidermal
cells, in the vicinity of the guard cells become specialised in their shape and
size and are known as subsidiary cells. The stomatal aperture, guard
cells and the surrounding subsidiary cells are together called stomatal
apparatus. The cells of epidermis bear a number of hairs. The root hairs are
unicellular elongations of the epidermal cells and help absorb water and
minerals from the soil. On the stem the epidermal hairs are called
trichomes. The trichomes in the shoot system are usually multicellular.
They may be branched or unbranched and soft or stiff. They may even
be secretory. The trichomes help in preventing water loss due to
transpiration.
⬆️Prev____@organised notes_____Next⬇️
.Which of the following has unevenly thick cell wall, has a primary wall (cellulose) and a secondary wall (hemicellulose or pectin), and is a simple, living, primarily mechanical tissue of the plant body?
1. Parenchyma
2. Collenchyma
3. Sclerenchyma
4. Aerenchyma
.
.
Answer ▽ ✅Verified
2. Collenchyma
Simple Tissues
A simple tissue is made of only one type of cells.The various simple tissues in plants are
parenchyma, collenchyma and sclerenchyma
.
Parenchyma forms the major
component within organs. The cells of the
parenchyma are generally isodiametric. They
may be spherical, oval, round, polygonal or
elongated in shape. Their walls are thin and made
up of cellulose. They may either be closely packed
or have small intercellular spaces. The
parenchyma performs various functions like
photosynthesis, storage, secretion.
The collenchyma occurs in layers below the
epidermis in most of the dicotyledonous plants. It is
found either as a homogeneous layer or in patches.
It consists of cells which are much thickened at the
corners due to a deposition of cellulose,
hemicellulose and pectin. Collenchymatous cells
may be oval, spherical or polygonal and often
contain chloroplasts. These cells assimilate food
when they contain chloroplasts. Intercellular spaces
are absent. They provide mechanical support to the
growing parts of the plant such as young stem and
petiole of a leaf. Collenchyma is unevenly thick cell wall, has a primary wall
component within organs. The cells of the
parenchyma are generally isodiametric. They
may be spherical, oval, round, polygonal or
elongated in shape. Their walls are thin and made
up of cellulose. They may either be closely packed
or have small intercellular spaces. The
parenchyma performs various functions like
photosynthesis, storage, secretion.
The collenchyma occurs in layers below the
epidermis in most of the dicotyledonous plants. It is
found either as a homogeneous layer or in patches.
It consists of cells which are much thickened at the
corners due to a deposition of cellulose,
hemicellulose and pectin. Collenchymatous cells
may be oval, spherical or polygonal and often
contain chloroplasts. These cells assimilate food
when they contain chloroplasts. Intercellular spaces
are absent. They provide mechanical support to the
growing parts of the plant such as young stem and
petiole of a leaf. Collenchyma is unevenly thick cell wall, has a primary wall
(cellulose) and a secondary wall (hemicellulose or pectin),
and is a simple, living, primarily mechanical tissue of the plant body.
Sclerenchyma consists of long, narrow cells
with thick and lignified cell walls having a few or
numerous pits. They are usually dead and without
protoplasts. On the basis of variation in form,
structure, origin and development, sclerenchyma
may be either fibres or sclereids. The fibres are
thick-walled, elongated and pointed cells,
generally occuring in groups, in various parts of
the plant. The sclereids are spherical, oval or
cylindrical, highly thickened dead cells with very
narrow cavities (lumen). These are commonly found in the fruit
walls of nuts; pulp of fruits like guava, pear and sapota; seed
coats of legumes and leaves of tea. Sclerenchyma provides
mechanical support to organs.
Sclerenchyma consists of long, narrow cells
with thick and lignified cell walls having a few or
numerous pits. They are usually dead and without
protoplasts. On the basis of variation in form,
structure, origin and development, sclerenchyma
may be either fibres or sclereids. The fibres are
thick-walled, elongated and pointed cells,
generally occuring in groups, in various parts of
the plant. The sclereids are spherical, oval or
cylindrical, highly thickened dead cells with very
narrow cavities (lumen). These are commonly found in the fruit
walls of nuts; pulp of fruits like guava, pear and sapota; seed
coats of legumes and leaves of tea. Sclerenchyma provides
mechanical support to organs.
⬆️Prev____@organised notes_____Next⬇️
.Identify the correct statement regarding collenchymas in plants:-
1. They occur in layers below the epidermis of monocotyledonous plants.
2. Cells are much thickened at the corners due to the deposition of lignin.
3. Collenchymatous cells do not contain chloroplasts.
4. They provide mechanical strength to the growing parts of the plant.
.
.
Answer ▽ ✅Verified
2. Cells are much thickened at the corners due to the deposition of lignin.
Simple Tissues
A simple tissue is made of only one type of cells.
The various simple tissues in plants are
parenchyma, collenchyma and sclerenchyma
. Parenchyma forms the major
component within organs. The cells of the
parenchyma are generally isodiametric. They
may be spherical, oval, round, polygonal or
elongated in shape. Their walls are thin and made
up of cellulose. They may either be closely packed
or have small intercellular spaces. The
parenchyma performs various functions like
photosynthesis, storage, secretion.
The collenchyma occurs in layers below the
epidermis in most of the dicotyledonous plants. It is
found either as a homogeneous layer or in patches.
It consists of cells which are much thickened at the
corners due to a deposition of cellulose,
hemicellulose and pectin. Collenchymatous cells
may be oval, spherical or polygonal and often
contain chloroplasts. These cells assimilate food
when they contain chloroplasts. Intercellular spaces
are absent. They provide mechanical support to the
growing parts of the plant such as young stem and
petiole of a leaf. Collenchyma is unevenly thick cell wall, has a primary wall (cellulose) and a secondary wall (hemicellulose or pectin), and is a simple, living, primarily mechanical tissue of the plant body.
Sclerenchyma consists of long, narrow cells
with thick and lignified cell walls having a few or
numerous pits. They are usually dead and without
protoplasts. On the basis of variation in form,
structure, origin and development, sclerenchyma
may be either fibres or sclereids. The fibres are
thick-walled, elongated and pointed cells,
generally occuring in groups, in various parts of
the plant. The sclereids are spherical, oval or
cylindrical, highly thickened dead cells with very
narrow cavities (lumen). These are commonly found in the fruit
walls of nuts; pulp of fruits like guava, pear and sapota; seed
coats of legumes and leaves of tea. Sclerenchyma provides
mechanical support to organs.
The various simple tissues in plants are
parenchyma, collenchyma and sclerenchyma
.
component within organs. The cells of the
parenchyma are generally isodiametric. They
may be spherical, oval, round, polygonal or
elongated in shape. Their walls are thin and made
up of cellulose. They may either be closely packed
or have small intercellular spaces. The
parenchyma performs various functions like
photosynthesis, storage, secretion.
The collenchyma occurs in layers below the
epidermis in most of the dicotyledonous plants. It is
found either as a homogeneous layer or in patches.
It consists of cells which are much thickened at the
corners due to a deposition of cellulose,
hemicellulose and pectin. Collenchymatous cells
may be oval, spherical or polygonal and often
contain chloroplasts. These cells assimilate food
when they contain chloroplasts. Intercellular spaces
are absent. They provide mechanical support to the
growing parts of the plant such as young stem and
petiole of a leaf. Collenchyma is unevenly thick cell wall, has a primary wall
Sclerenchyma consists of long, narrow cells
with thick and lignified cell walls having a few or
numerous pits. They are usually dead and without
protoplasts. On the basis of variation in form,
structure, origin and development, sclerenchyma
may be either fibres or sclereids. The fibres are
thick-walled, elongated and pointed cells,
generally occuring in groups, in various parts of
the plant. The sclereids are spherical, oval or
cylindrical, highly thickened dead cells with very
narrow cavities (lumen). These are commonly found in the fruit
walls of nuts; pulp of fruits like guava, pear and sapota; seed
coats of legumes and leaves of tea. Sclerenchyma provides
mechanical support to organs.
⬆️Prev____@organised notes_____Next⬇️
.In dicot roots, the initiation of the lateral roots and the vascular cambium during the secondary growth takes place in:
(1) Pericycle
(2) Endodermis
(3) Conjuctive tissue
(4) Epidermis
.
.
Answer ▽ ✅Verified
(1) Pericycle
- The Ground Tissue System
All tissues except epidermis and vascular bundles constitute the ground
tissue. It consists of simple tissues such as parenchyma, collenchyma
and sclerenchyma. Parenchymatous cells are usually present in cortex,
pericycle, pith and medullary rays, in the primary stems and roots. In
leaves, the ground tissue consists of thin-walled chloroplast containing
cells and is called mesophyll.
tissue. It consists of simple tissues such as parenchyma, collenchyma
and sclerenchyma. Parenchymatous cells are usually present in cortex,
pericycle, pith and medullary rays, in the primary stems and roots. In
leaves, the ground tissue consists of thin-walled chloroplast containing
cells and is called mesophyll.
The ground tissue system forms the main bulk of the
plant. It is divided into three zones – cortex, pericycle and pith.
- Dicotyledonous Root
The outermost layer is epiblema. Many of
the cells of epiblema protrude in the form of
unicellular root hairs. The cortex consists of
several layers of thin-walled parenchyma cellswith intercellular spaces. The innermostlayer of the cortex is called endodermis.It comprises a single layer of barrel-shapedcells without any intercellular spaces. Thetangential as well as radial walls of theendodermal cells have a deposition ofwater-impermeable, waxy material suberinin the form of casparian strips. Next toendodermis lies a few layers of thick-walledparenchyomatous cells referred to aspericycle. Initiation of lateral roots andvascular cambium during the secondarygrowth takes place in these cells. The pithis small or inconspicuous. Theparenchymatous cells which lie betweenthe xylem and the phloem are calledconjuctive tissue. There are usually twoto four xylem and phloem patches. Later,a cambium ring develops between thexylem and phloem. All tissues on theinnerside of the endodermis such aspericycle, vascular bundles and pithconstitute the stele.
- Monocotyledonous Root
The outermost layer is epiblema. Many of
the cells of epiblema protrude in the form of
unicellular root hairs. The cortex consists of
several layers of thin-walled parenchyma cells
the cells of epiblema protrude in the form of
unicellular root hairs. The cortex consists of
several layers of thin-walled parenchyma cells
with intercellular spaces. The innermost
layer of the cortex is called endodermis.
It comprises a single layer of barrel-shaped
cells without any intercellular spaces. The
tangential as well as radial walls of the
endodermal cells have a deposition of
water-impermeable, waxy material suberin
in the form of casparian strips. Next to
endodermis lies a few layers of thick-walled
parenchyomatous cells referred to as
pericycle. Initiation of lateral roots and
vascular cambium during the secondary
growth takes place in these cells. The pith
is small or inconspicuous. The
parenchymatous cells which lie between
the xylem and the phloem are called
conjuctive tissue. There are usually two
to four xylem and phloem patches. Later,
a cambium ring develops between the
xylem and phloem. All tissues on the
innerside of the endodermis such as
pericycle, vascular bundles and pith
constitute the stele.
- Monocotyledonous Root
The anatomy of the monocot root is similar
to the dicot root in many respects .
It has epidermis, cortex, endodermis,
pericycle, vascular bundles and pith. As
compared to the dicot root which have fewer
xylem bundles, there are usually more than
six (polyarch) xylem bundles in the monocot
root. Pith is large and well developed.
Monocotyledonous roots do not undergo
any secondary growth.
- Dicotyledonous Stem
The transverse section of a typical young
dicotyledonous stem shows that the epidermis
is the outermost protective layer of the stem.
Covered with a thin layer of cuticle, it may bear trichomes and
a few stomata. The cells arranged in multiple layers between epidermis and
pericycle constitute the cortex. It consists of three sub-zones. The outer
hypodermis, consists of a few layers of collenchymatous cells just below the
epidermis, which provide mechanical strength to the young stem. Cortical
layers below hypodermis consist of rounded thin walled parenchymatous
cells with conspicuous intercellular spaces. The innermost layer of the cortex
is called the endodermis. The cells of the endodermis are rich in starch
grains and the layer is also referred to as the starch sheath. Pericycle is
present on the inner side of the endodermis and above the phloem in the
form of semi-lunar patches of sclerenchyma. In between the vascular bundles
there are a few layers of radially placed parenchymatous cells, which constitute
medullary rays. A large number of vascular bundles are arranged in a ring ;
the ‘ring’ arrangement of vascular bundles is a characteristic of dicot stem.
Each vascular bundle is conjoint, open, and with endarch protoxylem. A
large number of rounded, parenchymatous cells with large intercellular
spaces which occupy the central portion of the stem constitute the pith.
- Secondary Growth in Roots
In the dicot root, the vascular
cambium is completely secondary in
origin. It originates from the tissue
located just below the phloem
bundles, a portion of pericycle tissue,
above the protoxylem forming a
complete and continuous wavy ring,
which later becomes circular . Further events are similar to
those already described above for a
dicotyledon stem.
- Development of root nodules in soyabean
Infected thread carries the bacteria
to the inner cortex. The bacteria get modified into rod-shaped
bacteroids and cause inner cortical and pericycle cells to divide.
Division and growth of cortical and pericycle cells lead to nodule
formation,
⬆️Prev____@organised notes_____Next⬇️
.In dicot stem the vascular bundle is:-
1. Conjoint, open and with exarch protoxylem.
2. Conjoint, open and with endarch protoxylem.
3. Conjoint and closed.
4. Scattered, each surrounded by a sclerenchymatous bundle sheath.
.
.
Answer ▽ ✅Verified
2. Conjoint, open and with endarch protoxylem.
Primary xylem is of two types – protoxylem and metaxylem.
The first formed primary xylem elements are called protoxylem
and the later formed primary xylem is called metaxylem. In
stems, the protoxylem lies towards the centre (pith) and the
metaxylem lies towards the periphery of the organ. This type
of primary xylem is called endarch: from endo- + Greek arkhē beginning..
The first formed primary xylem elements are called protoxylem
and the later formed primary xylem is called metaxylem. In
stems, the protoxylem lies towards the centre (pith) and the
metaxylem lies towards the periphery of the organ. This type
of primary xylem is called endarch: from endo- + Greek arkhē beginning..
In roots, the protoxylem
lies towards periphery and metaxylem lies towards the centre.
Such arrangement of primary xylem is called exarch.
Such arrangement of primary xylem is called exarch.
A large number of vascular bundles are arranged in a ring ;
the ‘ring’ arrangement of vascular bundles is a characteristic of dicot stem.
Each vascular bundle is conjoint, open, and with endarch protoxylem.
In conjoint type of vascular
bundles, the xylem and phloem are jointly
situated along the same radius of vascular
bundles. Such vascular bundles are common
in stems and leaves. The conjoint vascular
bundles usually have the phloem located only
on the outer side of xylem.
In dicotyledonous stems, cambium
is present between phloem and xylem. Such
vascular bundles because of the presence of
cambium possess the ability to form secondary
xylem and phloem tissues, and hence are called
open vascular bundles. In the monocotyledons,
the vascular bundles have no cambium present
in them. Hence, since they do not form secondary
tissues they are referred to as closed.
⬆️Prev____@organised notes_____Next⬇️
.Bulliform cells:
1. Are found in dorsiventral leaves and help in photosynthesis.
2. Are found in dorsiventral leaves and help in minimizing water loss.
3. Are found in isobilatetral leaves and help in minimizing water loss.
4. Are found in isobilatetral leaves and help in photosynthesis.
.
.
Answer ▽ ✅Verified
3. Are found in isobilatetral leaves and help in minimizing water loss.
Isobilateral (Monocotyledonous) Leaf
The anatomy of isobilateral leaf is similar to that of the dorsiventral leaf in
many ways. It shows the following characteristic differences. In an
isobilateral leaf, the stomata are present
on both the surfaces of the epidermis; and
the mesophyll is not differentiated into
palisade and spongy parenchyma
In grasses, certain adaxial epidermal
cells along the veins modify themselves
into large, empty, colourless cells. These
are called bulliform cells. When the
bulliform cells in the leaves have absorbed
water and are turgid, the leaf surface is
exposed. When they are flaccid due to
water stress, they make the leaves curl
inwards to minimise water loss.
The parallel venation in monocot
leaves is reflected in the near similar sizes
of vascular bundles (except in main veins)
as seen in vertical sections of the leaves.
many ways. It shows the following characteristic differences. In an
isobilateral leaf, the stomata are present
on both the surfaces of the epidermis; and
the mesophyll is not differentiated into
palisade and spongy parenchyma
In grasses, certain adaxial epidermal
cells along the veins modify themselves
into large, empty, colourless cells. These
are called bulliform cells. When the
bulliform cells in the leaves have absorbed
water and are turgid, the leaf surface is
exposed. When they are flaccid due to
water stress, they make the leaves curl
inwards to minimise water loss.
The parallel venation in monocot
leaves is reflected in the near similar sizes
of vascular bundles (except in main veins)
as seen in vertical sections of the leaves.
⬆️Prev____@organised notes_____Next⬇️
.During secondary growth in the stem:-
1. The amount of secondary xylem produced is more than the secondary phloem as the cambium is generally more active on the inner side than the outer.
2. the amount of secondary phloem produced is more than the secondary xylem as the cambium is generally more active on the inner side than the outer.
3. the amount of secondary xylem produced is more than the secondary phloem as the cambium is generally more active on the outer side than the inner.
4. the amount of secondary phloem produced is more than the secondary xylem as the cambium is generally more active on the outer side than the inner.
.
.
Answer ▽ ✅Verified
1. The amount of secondary xylem produced is more than the secondary phloem as the cambium is generally more active on the inner side than the outer.
SECONDARY GROWTH
The growth of the roots and stems in
length with the help of apical meristem is
called the primary growth. Apart from
primary growth most dicotyledonous
plants exhibit an increase in girth. This
increase is called the secondary growth.
The tissues involved in secondary growth
are the two lateral meristems: vascular
cambium and cork cambium.
length with the help of apical meristem is
called the primary growth. Apart from
primary growth most dicotyledonous
plants exhibit an increase in girth. This
increase is called the secondary growth.
The tissues involved in secondary growth
are the two lateral meristems: vascular
cambium and cork cambium.
⬆️Prev____@organised notes_____Next⬇️
.Identify the incorrect statement:
1. The presence of vessels is a characteristic of angiosperms
2. In roots the primary xylem is exarch
3. Gymnosperms lack albuminous cells and sieve cells
4. Bast fibers are generally absent in primary phloem
.
.
Answer ▽ ✅Verified
3. Gymnosperms lack albuminous cells and sieve cells
⬆️Prev____@organised notes_____Next⬇️
.Lignin is a component of the secondary walls of:-
1. Epidermis
2. Collenchyma
3. Sclerenchyma
4. Parenchyma
.
.
Answer ▽ ✅Verified
3. Sclerenchyma
Simple Tissues
A simple tissue is made of only one type of cells.The various simple tissues in plants are
parenchyma, collenchyma and sclerenchyma
.
Parenchyma forms the major
component within organs. The cells of the
parenchyma are generally isodiametric. They
may be spherical, oval, round, polygonal or
elongated in shape. Their walls are thin and made
up of cellulose. They may either be closely packed
or have small intercellular spaces. The
parenchyma performs various functions like
photosynthesis, storage, secretion.
The collenchyma occurs in layers below the
epidermis in most of the dicotyledonous plants. It is
found either as a homogeneous layer or in patches.
It consists of cells which are much thickened at the
corners due to a deposition of cellulose,
hemicellulose and pectin. Collenchymatous cells
may be oval, spherical or polygonal and often
contain chloroplasts. These cells assimilate food
when they contain chloroplasts. Intercellular spaces
are absent. They provide mechanical support to the
growing parts of the plant such as young stem and
petiole of a leaf. Collenchyma is unevenly thick cell wall, has a primary wall
component within organs. The cells of the
parenchyma are generally isodiametric. They
may be spherical, oval, round, polygonal or
elongated in shape. Their walls are thin and made
up of cellulose. They may either be closely packed
or have small intercellular spaces. The
parenchyma performs various functions like
photosynthesis, storage, secretion.
The collenchyma occurs in layers below the
epidermis in most of the dicotyledonous plants. It is
found either as a homogeneous layer or in patches.
It consists of cells which are much thickened at the
corners due to a deposition of cellulose,
hemicellulose and pectin. Collenchymatous cells
may be oval, spherical or polygonal and often
contain chloroplasts. These cells assimilate food
when they contain chloroplasts. Intercellular spaces
are absent. They provide mechanical support to the
growing parts of the plant such as young stem and
petiole of a leaf. Collenchyma is unevenly thick cell wall, has a primary wall
(cellulose) and a secondary wall (hemicellulose or pectin),
and is a simple, living, primarily mechanical tissue of the plant body.
Sclerenchyma consists of long, narrow cells
with thick and lignified cell walls having a few or
numerous pits. They are usually dead and without
protoplasts. On the basis of variation in form,
structure, origin and development, sclerenchyma
may be either fibres or sclereids. The fibres are
thick-walled, elongated and pointed cells,
generally occuring in groups, in various parts of
the plant. The sclereids are spherical, oval or
cylindrical, highly thickened dead cells with very
narrow cavities (lumen). These are commonly found in the fruit
walls of nuts; pulp of fruits like guava, pear and sapota; seed
coats of legumes and leaves of tea. Sclerenchyma provides
mechanical support to organs.
Sclerenchyma consists of long, narrow cells
with thick and lignified cell walls having a few or
numerous pits. They are usually dead and without
protoplasts. On the basis of variation in form,
structure, origin and development, sclerenchyma
may be either fibres or sclereids. The fibres are
thick-walled, elongated and pointed cells,
generally occuring in groups, in various parts of
the plant. The sclereids are spherical, oval or
cylindrical, highly thickened dead cells with very
narrow cavities (lumen). These are commonly found in the fruit
walls of nuts; pulp of fruits like guava, pear and sapota; seed
coats of legumes and leaves of tea. Sclerenchyma provides
mechanical support to organs.
⬆️Prev____@organised notes_____Next⬇️
.The vascular bundle shown in the diagram is most likely to be seen in:
(1) Monocot stem
(2) Dicot stem
(3) Monocot root
(4) Dicot root
.
.
Answer ▽ ✅Verified
(2) Dicot stem
⬆️Prev____@organised notes_____Next⬇️
.The main function of the plant tissue shown below is:
(1) Storage of nutrients
(2) Providing buoyancy to submerged plants
(3) Mechanical support to growing parts of a plant
(4) Increase in the length of the plant
.
Answer ▽ ✅Verified
(3) Mechanical support to growing parts of a plant
⬆️Prev____@organised notes_____Next⬇️
.Identify the wrong statement in context of heartwood.
(1) Organic compounds are deposited in it
(2) it is highly durable
(3) It conducts water and minerals efficiently
(4) It comprises dead elements with highly lignified walls
.
.
Answer ▽ ✅Verified
(3) It conducts water and minerals efficiently
Heartwood and sapwood
In old trees, the greater part of secondary xylem is dark brown due todeposition of organic compounds like tannins, resins, oils, gums, aromaticsubstances and essential oils in the central or innermost layers of the stem.These substances make it hard, durable and resistant to the attacks of microorganismsand insects. This region comprises dead elements with highlylignified walls and is called heartwood. The heartwood does not conductwater but it gives mechanical support to the stem. The peripheral region ofthe secondary xylem, is lighter in colour and is known as the sapwood. It isinvolved in the conduction of water and minerals from root to leaf.
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.The vascular cambium normal gives rise to.
(1) phelloderm
(2) primary phloem
(3) secondary xylem
(4) periderm
.
.
Answer ▽ ✅Verified
(3) secondary xylem
➡️Activity of the cambial ring
The cambial ring becomes active and begins to cut off new cells, both
towards the inner and the outer sides. The cells cut off towards pith,
mature into secondary xylem and the cells cut off towards periphery
mature into secondary phloem. The cambium is generally more active
on the inner side than on the outer. As a result, the amount of secondary
xylem produced is more than secondary phloem and soon forms a
compact mass. The primary and secondary phloems get gradually
crushed due to the continued formation and accumulation of secondary
xylem. The primary xylem however remains more or less intact, in or
around the centre. At some places, the cambium forms a narrow band of
parenchyma, which passes through the secondary xylem and the
secondary phloem in the radial directions. These are the secondary
medullary rays
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.Cortex is the region found between
(1) Epidermis and stele
(2) Pericycle and endodermis
(3) Endodermis and pith
(4) Endodermis and vascular bundle
.
.
Answer ▽ ✅Verified
(1) Epidermis and stele
➡️Dicotyledonous Root
The internal tissue
organisation is as follows:
The outermost layer is epiblema. Many of
the cells of epiblema protrude in the form of
unicellular root hairs. The cortex consists of
several layers of thin-walled parenchyma cells
with intercellular spaces. The innermost
layer of the cortex is called endodermis.
It comprises a single layer of barrel-shaped
cells without any intercellular spaces. The
tangential as well as radial walls of the
endodermal cells have a deposition of
water-impermeable, waxy material suberin
in the form of casparian strips. Next to
endodermis lies a few layers of thick-walled
parenchyomatous cells referred to as
pericycle. Initiation of lateral roots and
vascular cambium during the secondary
growth takes place in these cells. The pith
is small or inconspicuous. The
parenchymatous cells which lie between
the xylem and the phloem are called
conjuctive tissue. There are usually two
to four xylem and phloem patches. Later,
a cambium ring develops between the
xylem and phloem. All tissues on the
innerside of the endodermis such as
pericycle, vascular bundles and pith
constitute the stele.
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.Vascular bundles in monocotyledons are considered closed because
1. a bundle sheath surrounds each bundle
2. cambium is absent
3. there are no vessels with performations
4. xylem is surrounded all around by phloem
.
.
Answer ▽ ✅Verified
2. cambium is absent
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.Interfascicular cambium develops from the cells of ?
1. medullary rays
2. xylem parenchyma
3. endodermis
4. pericycle
.
.
Answer ▽ ✅Verified
1. medullary rays
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.Companion cells are closely associated with
(1) sieve elements
(2) vessel elements
(3) trichomes
(4) guard cells
.
.
Answer ▽ ✅Verified
(1) sieve elements
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.Closed vascular bundles lack
(1) ground tissue
(2) conjunctive tissue
(3) cambium
(4) pith
.
.
Answer ▽ ✅Verified
(3) cambium
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.Ground tissues includes
1. All tissues except epidermis and vascular bundles
2. Epidermis and cortex
3. All tissues internal to endodermis
4. All tissues external to endodermis
.
.
Answer ▽ ✅Verified
1. All tissues except epidermis and vascular bundles
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.The cork cambium, cork and secondary cortex are collectively called
1. phellogen
2. periderm
3. phellem
4. phelloderm
.
.
Answer ▽ ✅Verified
2. periderm
➡️Cork Cambium
As the stem continues to increase in girth due to the activity of vascular
cambium, the outer cortical and epidermis layers get broken and need to
be replaced to provide new protective cell layers. Hence, sooner or later,
another meristematic tissue called cork cambium or phellogen develops,
usually in the cortex region. Phellogen is a couple of layers thick. It is
made of narrow, thin-walled and nearly rectangular cells. Phellogen cuts
off cells on both sides. The outer cells differentiate into cork or phellem
while the inner cells differentiate into secondary cortex or phelloderm.
The cork is impervious to water due to suberin deposition in the cell wall.
The cells of secondary cortex are parenchymatous. Phellogen, phellem,
and phelloderm are collectively known as periderm. Due to activity of
the cork cambium, pressure builds up on the remaining layers peripheral
As the stem continues to increase in girth due to the activity of vascular
cambium, the outer cortical and epidermis layers get broken and need to
be replaced to provide new protective cell layers. Hence, sooner or later,
another meristematic tissue called cork cambium or phellogen develops,
usually in the cortex region. Phellogen is a couple of layers thick. It is
made of narrow, thin-walled and nearly rectangular cells. Phellogen cuts
off cells on both sides. The outer cells differentiate into cork or phellem
while the inner cells differentiate into secondary cortex or phelloderm.
The cork is impervious to water due to suberin deposition in the cell wall.
The cells of secondary cortex are parenchymatous. Phellogen, phellem,
and phelloderm are collectively known as periderm. Due to activity of
the cork cambium, pressure builds up on the remaining layers peripheral
to phellogen and ultimately these
layers die and slough off. Bark is a
non-technical term that refers to all
tissues exterior to the vascular
cambium, therefore including
secondary phloem. Bark refers to a
number of tissue types, viz.,
periderm and secondary phloem.
Bark that is formed early in the
season is called early or soft bark.
Towards the end of the season, late
or hard bark is formed. Name the
various kinds of cell layers which
constitute the bark.
At certain regions, the phellogen
cuts off closely arranged
parenchymatous cells on the outer
side instead of cork cells. These
parenchymatous cells soon rupture
the epidermis, forming a lensshaped
openings called lenticels.
Lenticels permit the exchange of
gases between the outer atmosphere
and the internal tissue of the stem.
These occur in most woody trees
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.Which one of the following is not a lateral meristem?
1. Cork cambium
2. Interfascicular cambium
3. Phellogen
4. Intercalary meristem
.
.
Answer ▽ ✅Verified
4. Intercalary meristem
Fascicular vascular cambium,
interfascicular cambium and cork-cambium are examples of lateral
meristems.
secondary or lateral meristem.
They are cylindrical meristems.
interfascicular cambium and cork-cambium are examples of lateral
meristems.
secondary or lateral meristem.
They are cylindrical meristems.
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.In the given diagram of section of root of maize, different parts have been indicated by alphabets. Choose the answer in which these alphabets have been correctly matched with the parts which they indicate.
1. A = Phloem, B = Xylem, C = Cortex, D = Endodermis, E = Pith, F = Root hair, G =
Epidermis
2. A = Pith, B = Root hair, C = Epiblema, D = Cortex, E = Endodermis, F = Phloem, G
= Xylem
3. A = Root hair, B = Epiblema, C = Cortex, D = Endodermis, E = Pith, F = Xylem, G
= Phloem
4. A = Epiblema, B = Root hair, C = Vascular bundle, D = Cortex, E = Phloem, F =
Xylem, G = Pith
.
.
Answer ▽ ✅Verified
3. A = Root hair, B = Epiblema, C = Cortex, D = Endodermis, E = Pith, F = Xylem, G
= Phloem
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.Fascicular cambium separates the xylem and phloem in:-
1. only dicots
2. only monocots
3. both dicots and monocots
4. none of the above.
.
.
Answer ▽ ✅Verified
1. only dicots
The meristem that occurs in the mature regions of roots and shoots of
many plants, particularly those that produce woody axis and appear
later than primary meristem is called the secondary or lateral meristem.
They are cylindrical meristems. Fascicular vascular cambium,
interfascicular cambium and cork-cambium are examples of lateral
meristems. These are responsible for producing the secondary tissues
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.
.
.
Answer ▽ ✅Verified
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.In a plant organ which is covered by periderm and in which the stomata are absent, some gaseous exchange still takes place through.
(1) aerenchyma
(2) trichomes
(3) pneumatophores
(4) lenticels
.
.
Answer ▽ ✅Verified
(4) lenticels
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.Which of the following is not true about Sclereids?
A. These are parenchyma cells with thick lignified walls
B. These are are spherical, oval or cylindrical, highly thickened dead cells
C. These are commonly found in shells of nuts and in pulp of guava, pear, etc
D. These are also called stone cells
.
.
Answer ▽ ✅Verified
A. These are parenchyma cells with thick lignified walls
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.During the formation of leaves and elongation of stem, some cells left behind from shoot apical meristem constitute _____________
(1) Axillary bud
(2) Lateral bud
(3) Apical bud
(4) Protoderm
.
.
Answer ▽ ✅Verified
(1) Axillary bud
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