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CBSE Questions for Class 11 Medical Biology Anatomy Of Flowering Plants Quiz 4 - MCQExams.com
CBSE
Class 11 Medical Biology
Anatomy Of Flowering Plants
Quiz 4
The waxy material deposited in the Casparian strip of the endodermis is
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0%
Pectin
0%
Suberin
0%
Cellulose
0%
Lignin
0%
Hemicellulose
Explanation
The waxy material deposited in the Casparian strip of the endodermis is suberin. The Casparian strip is a band of cell wall material deposited on the radial and transverse walls of the endodermis, and is chemically different from the rest of the cell wall - the cell wall being made of lignin and without suberin, whereas the Casparian strip is made of suberin and sometimes lignin. It blocks the passive flow of materials such as water and solutes into the stele of a plant.
Thus, the correct answer is option B.
Starch sheath is
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Endodermis of monocot stem
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Endodermis of dicot stem
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Petiole of a leaf
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Endodermis of monocot root
Explanation
The endodermis of the dicot stem is the central, innermost layer of the cortex.
The endodermis is made up of barrel-shaped cells which do not enclose intercellular space.
The endodermis helps to regulate the movement of water, ions, and hormones into and out of the vascular system. It may also store starch grains as a food reserve.
Thus, the stem of the endodermis of the dicot stem is called starch sheath.
So, the correct answer is option B.
Which of the following is an epidermal cell?
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Guard cell
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Root hair
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Trichome
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All of the above
Explanation
Guard cells are modified epidermal cells, root hairs are epidermal extensions and trichome is an epidermal appendage. The epidermis cells is a single-layered group of cells that covers plants' leaves, flowers, roots and stems. It forms a boundary between the plant and the external environment. The epidermis serves several functions, it protects against water loss, regulates gas exchange, secretes metabolic compounds and absorbs water and mineral nutrients.
Thus, the correct answer is option D.
Distinguishing feature of closed vascular bundle is
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Presence of cambium
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Absence of cambium
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Ring of vascular bundles
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No vascular bundles
Explanation
Open vascular bundle contains an interfascicular cambium in between phloem and xylem. Phloem and xylem are not in direct contact with each other.
In closed vascular bundle interfascicular cambium is absent. There is direct contact between phloem and xylem.
The continuous cytoplasmic system running through the sieve tubes is called as
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Symplast
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Ectoplast
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Protoplast
0%
Endoplast
Procambium forms the
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Cork cambium
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Vascular tissue
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Vascular cambium
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Intercalary meristem
Explanation
Procambium
forms the vascular cambium. The procambium is a meristematic tissue concerned with providing the primary tissues of the vascular system. The procambium differentiates into the vascular tissues, that is xylem, phloem, and vascular cambium. The xylem and phloem are conducting and supporting vascular tissues.
Thus, the correct answer is option B.
Identify the correct statement with reference to pericycle?
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Distinguished in monocot stems
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Innermost layer of the cortex
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Partly sclerenchymatous in roots
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The seat of origin of lateral roots
Explanation
In monocots, cortex is differentiated into hypodermis, general cortex, endodermis and stele is not differentiated into pericycle, vascular bundles, medulla and medullary rays.
Pericycle in roots may be mostly composed of parenchyma cells.
The pericycle regulates the formation of lateral roots by rapidly dividing near the xylem elements of the root. It has been known to often be confused with other parts of the plant.
Thus, the right option is D.
Jute fibres cannot deteriorate quickly because
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Cellulose content is high
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Lignin content is high
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Cellulose content is low
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Lignin content is low
Explanation
The basic constituent of jute is cellulose and lignin. Both bacteria and fungi can decompose cellulose depending upon the moisture content. The resistance to microbial damage thus depends mostly on lignin. The higher the lignin content, the more resistant the fibre will be to rotting i.e. fungal attack, which will then result in less deterioration.
So, the correct answer is option B.
The Tunica-Corpus theory was proposed by
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Haberlandt
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Schmidt
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Hanstein
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Nageli
Explanation
Schmidt proposed t
he Tunica-Corpus theory which focused on the pattern of growth of tissues present at the apex.
Tunica-Corpus theory was proposed by Schmidt. According to this theory, two tissue zones occur at the apex. They are the Tunica, consisting of one or more layers of cells forming the outer enveloping region and the corpus the central core.
Therefore, the correct answer is option B.
Conjoint, collateral, closed and endarch vascular bundles scattered in the ground tissue are found in
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Dicot root
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Monocot root
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Dicot stem
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Monocot stem
Explanation
Conjoint, collateral, closed and endarch vascular bundles scattered in the ground tissue are found in monocot stem. In a monocotyledenous stem the vascular bundles are not arranged in a circle but are usually scattered throughout the ground tissue. There is no clearly defined pith as there is in many dicotyledonous species. The vascular bundles of monocotylenous plants do not contain a layer of meristematic tissue.
Cortex and pith remain indistinguishable in
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Monocot stem
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Monocot root
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Periderm
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Dicot stem
Explanation
Cortex and pith remain indistinguishable in a monocot stem. The epidermis is a layer of cells that cover the plant body, including the stems, leaves, flowers and fruits, that protects the plant from the outside world. In old stems the epidermal layer, cortex and primary phloem become separated from the inner tissues by thicker formations of cork. But in the monocots the cortex and pith are indistinguishable.
Therefore, the correct answer is option A.
Sclerenchyma is a simple permanent tissue with thick secondary lignified cell walls.
Which one of the following statements regarding sclerenchyma is not correct?
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Sclerenchyma fibres associated with xylem tissue are called as wood fibres
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Sclerenchyma fibres associated with phloem tissue are called as bast fibres
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Endocarp of coconut is rich in sclerenchyma fibres
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Brachysclereids are isodiametric and polygonal
Sclerenchymatous bundle sheath is found in
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Sunflower
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Mango
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Grass
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Banyan
Explanation
The bundle sheath of monocot leaf is made of parenchyma but just above and below the vascular bundles are found sclerenchymatous cells up to epidermis.
The bundle sheath of dicot leaf is made of parenchyma. Just above and below the vascular bundle, some parenchymatous cells or collenchymatous cells are present up to epidermis.
Grass is a monocot and contains sclerenchymatous bundle sheath.
Sunflower, banyan and mango are dicots and contains parenchymatous or collenchymatous bundle sheath.
Thus, the correct answer is option C.
One of the following is wrong for comparison between dicot and monocot stem. In dicot stem
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Vascular bundles are arranged in ring and in monocots they are scattered
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Vascular bundles are oval and in monocots wedge shaped
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True pith is present and absent in monocot stem
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There is no protoxylem lacuna
Explanation
Presence of scattered, oval vascular bundles is characteristic feature of a monocot stem. Dicot stem has wedged shaped vascular bundles arranged in ring.
Dicot stem has pith with thin walled parenchymatous cells but monocot stem lack it.
Both monocot and dicot stem has endarch xylem in which xylem formed first is present near the centre and is termed as protoxylem, while metaxylem is present towards the periphery.
Xylem in monocot is arranged as 'Y'shape with two metaxylem vessels are situated at the upper two arms and one / two protoxylem vessels at the bottom.
Disintegration of the lowest protoxylem creates a cavity, the protoxylem lacuna, which is absent in dicots.
A narrow layer consisting of thin-walled cells which separates the wood from phloem in dicot stem is called as
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Pericycle
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Cambium
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Endodermis
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Phellogen
Explanation
A narrow layer consisting of thin-walled cells which separates the wood from phloem in dicot stem is called as cambium
.
The vascular cambium is a lateral meristem in the vascular tissue of plants. It is a cylinder of unspecialized meristem cells that divide to give rise to cells that differentiate to form the secondary vascular tissues. The vascular cambium is the source of both the secondary xylem and the secondary phloem and is located between these tissues in the stem and root. The cambium present between primary xylem and primary phloem is called as intrafasicular cambium.
Therefore, the correct answer is option B.
In a young dicot stem epidermis is covered by a waxy coating, called as
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Pectin
0%
Suberin
0%
Cuticle
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None of the above
Explanation
In a young dicot stem epidermis is covered by a waxy coating, called as cuticle. Cuticle is the waxy coating of the outer walls of epidermal cells of stem. It's function is to protect against excessive water loss, as well as protecting against mechanical injury.
Hypodermis in dicot stem is composed of
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Parenchyma
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Collenchyma
0%
Sclerenchyma
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Both (B) and (C)
Explanation
Hypodermis is a region lying immediately below the epidermis. It is represented by a few layers of collenchyma cells with angular thickenings. The cells are compactly arranged without any intercellular spaces. Hypodermis provides mechanical support and additional protection. So, hypodermis of a dicot stem is composed of collenchyma and not parenchyma or sclerenchyma.
Thus, the correct answer is option B.
A dicot root differs from a monocot root in presence of
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Piliferous layer
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Exodermis
0%
Under-developed pith
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Separate vascular bundle
Explanation
Pith is very small, with closely packed parenchyma cells in dicot root. In monocot root pith and conjunctive tissue, become lignified and sclerenchymatous and it is relatively large.
The youngest layer of secondary xylem in a five year old dicot stem is found
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Just outside the cambium
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Just inside the cambium
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Adjacent to pith
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Adjacent to cortex
Explanation
In a dicot stem, by the end of the first year, the primary structure shows the growth of vascular and cork cambiums. The growth of the secondary xylem becomes continuous with the primary xylem. The secondary growth occurs both in the stele and cortex and though simultaneously, is caused by separate strips of secondary meristem. The cambial ring exhibits mitotic activity on both the sides and ones towards the inner surface results in the formation of xylem cells.
Ground tissue includes
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All tissues internal to endodermis
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All tissues external to endodermis
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All tissues except epidermis and vascular bundles
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Epidermis and cortex
Explanation
Correct option: C
Explanation:
Based upon the type of cell walls, ground tissue is subdivided into-
parenchyma, collenchyma and sclerenchyma
.
These all are present between the epidermis and the vascular bundles.
Parenchyma cell
s remain alive on maturation.
Collenchyma and Sclerenchyma cells
are mostly dead and have thickenings.
Hence, g
round tissue includes "
a
ll tissues except epidermis and vascular bundles".
Intercalary meristem at base of
Pinus
leaves or nodes of grasses is responsible for
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Primary growth
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Secondary growth
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Phellem formation
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Abscission formation
Explanation
Intercalary meristem
at base of leaves or nodes of grasses is responsible for primary growth. Meristems are classified by their location in the plant as apical located at root and shoot tips, lateral in the vascular and cork cambia, and intercalary at internodes or stem regions between the places at which leaves attach, and leaf bases. Intercalary meristem cells possess the ability to divide and produce new cells, as do apical and lateral meristems. They differ, however, in being situated between regions of mature tissue, such as at the base of grass leaves, which are themselves located on mature stem tissue.
Therefore, the correct answer is option A.
Collenchymatous hypodermis is characteristic feature of
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Dicot stem
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Monocot stem
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Monocot as well as dicot stem
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Hydrophytes
Explanation
Hypodermis is a region lying immediately below the epidermis. It is represented by a few layers of collenchyma cells with angular thickenings in dicot stem. The cells are compactly arranged without any intercellular spaces. Hypodermis provides mechanical support and additional protection. Thus, option A is correct.
Sclerenchymatous hypodermis is present in monocot stem.
Hypodermis in hydrophytes is poorly developed and is not collenchymatous.
Fibre , the longest plant cell belongs to which tissue?
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Parenchyma
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Collenchyma
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Sclerenchyma
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Aerenchyma
Explanation
Sclerenchyma is a simple permanent tissue which is mainly composed of dead cells. The walls consist of cellulose, hemicellulose and lignin. These are the principal supporting cells in plant tissues that have ceased elongation.
Sclerenchyma fibres are of great economical importance, since they constitute the source material for many fabrics (flax, hemp, jute, ramie).
So, the correct answer is option C.
The character of monocot is
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Net-veined leaves
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Annual rings
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Seed with two masses of stored food
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Conducting strands scattered in ground tissue
Explanation
Net-veined leaves, annual rings and seed with two masses of stored food are characteristic features of dicots.
In a monocotyledenos, the vascular bundles are not arranged in a circle but are usually scattered throughout the ground tissue. There is no clearly defined pith as there is in many dicotyledonous species. The vascular bundles of monocotylenous plants do not contain a layer of meristematic tissue (cambium) as the dicots do. Thus, no new cells can be formed inside the vascular bundles of monocots and their vascular bundles are termed as closed, whereas those of dicot plants are open.
Stems of few dicot plants are getting mechanical strength mainly because of ......... tissue, before secondary growth.
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Sclerenchyma
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Collenchyma
0%
Parenchyma
0%
None of the above
Explanation
Collenchyma tissue is composed of elongated cells with irregularly thickened walls. They provide structural support, particularly in growing shoots and leaves. Collenchyma tissue makes up things such as the resilient strands in stalks of celery. Collenchyma cells are usually living and have only a thick primary cell wall made up of cellulose and pectin. Cell wall thickness is strongly affected by mechanical stress upon the plant. Collenchyma cells are most often found adjacent to outer growing tissues such as the vascular cambium and are known for increased structural support and integrity. So, the stems of few dicot plants are getting mechanical strength mainly because of collenchyma before secondary growth. Parenchyma is a versatile ground tissue that generally constitutes the filler tissue in soft parts of plants. It forms, among other things, the cortex and pith of stems, the cortex of roots, the mesophyll of leaves, the pulp of fruits, and the endosperm of seeds. Sclerenchyma is the supporting tissue in plants after secondary growth.
Thus, the correct answer is option B.
In dicotyledonous roots, the initiation of lateral roots takes place in
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Endodermal cells
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Cortical cells
0%
Epidermal cells
0%
Procambial cells
0%
Pericycle cells
Explanation
The pericycle is a cylinder of parenchyma or sclerenchyma cells that lies just inside the endodermis and is the outer most part of the stele of plants. Although it is composed of non-vascular parenchyma cells, it is still considered part of the vascular cylinder, because it arises from the procambium as do the vascular tissues it surrounds.
In dicot stems, the pericycle strengthens the stem and provides protection for the vascular bundles.
In dicot roots, the vascular cambium is completely secondary in origin and it originates from a portion of pericycle tissue. Since it has the capacity to produce lateral roots, the pericycle also, therefore, regulates the formation of lateral roots.
Resin ducts are found in
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Pine
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Bamboos
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Teak
0%
Sal
Explanation
Resin canals is an o
pen, tube-like spaces bordered by special cells. These are tubular and helps in secretion at a particular specific site so these are also known as resin ducts. These can be specifically traced in conifers. These
have the ability to secrete pitch or resin into the neighboring opening (canal) forms the resin duct. One of the apparent purposes of these ducts is to protect and seal up a wound by exuding resin to cover the damaged area of the tree.
Pines are evergreen, coniferous resinous trees (or, rarely, shrubs) growing 3–80 m (10–260 ft) tall.
So, the correct answer is option A.
Meristem present at lamina margin is
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Apical meristem
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Intercalary meristem
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Mass meristem
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Marginal meristem
Explanation
A meristem is made of dividing cells. They are in parts of the plant where growth can take place. Marginal meristem is present in leaf margins for growth to occur.
Hence the correct option is D.
Torus is composed of
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Suberin
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Chitin
0%
Cutin
0%
Lignin
Explanation
Torus is composed of suberin. Torus is the thickened part of a stem, the receptacle, from which the flower and fruit parts grow. Torus, a structure of the xylem. Suberin is highly hydrophobic and a somewhat rubbery material. Its main function is to prevent water from penetrating the tissue. In roots, suberin is deposited in the radial and transverse cell walls of the endodermal cells.
Thus, the correct answer is option A.
In roots, the pericycle gives rise to:
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Lateral roots and cork cambium
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Cortex and pith
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Xylem and phloem
0%
Epidermis and vascular bundles
Explanation
Pericycle is a primary tissue of plant roots and is the site for the initiation of lateral roots and two secondary meristems, the vascular cambium and cork cambium (phellogen).
The pericycle is a cylinder of parenchyma or sclerenchyma cells that lies just inside the endodermis and is the outer most part of the stele of plants. Although it is composed of non-vascular parenchyma cells, it is still considered part of the vascular cylinder, because it arises from the procambium as do the vascular tissues it surrounds.
In dicots, it also has the capacity to produce lateral roots. Branch roots arise from this primary meristem tissue. In plants undergoing secondary growth, the pericycle contributes to the vascular cambium often diverging into a cork cambium
So, the correct answer is '
Lateral roots and cork cambium'
In general, the cells of cortex lack
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Chlorophyll
0%
Nucleus
0%
Reserve food
0%
Nucleolus
Explanation
Cortex is the ground tissue present between epidermis and endodermis. It is mostly composed of parenchymatous cells. Parenchymatous cells are thin walled polyhedral, isodiametric living cells with sufficient cytoplasm, one or more nuclei and nucleolus. They serve to store food.
Chlorophyll is present in
chlorenchyma
which are specialized to perform photosynthesis and are present in leaves. Thus, the correct answer is option A.
Growth rings are formed due to the activity of
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Intrastelar Cambium
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Intercalary Cambium
0%
Extrastelar cambium
0%
Primary cambium
Explanation
As we know that Intrafascicular or intrastelar cambium is present between xylem and phloem in dicot stem and roots. Pith rays, present between the edges of intrafascicular cambium, divide to form a new cambium strip between the two vascular bundle i.e. interfascicular cambium. Thus, inter and intra fascicular cambium together forms a complete cambium ring called as vascular cambium or just cambium which forms secondary xylem on inner side and secondary phloem on outer side. Differential cambial activity during autumn and spring season result in narrow and wide secondary xylem rings respectively which together forms the annual growth ring. Thus annual growth ring is derived from vascular cambium which is derived from inter and intrastelar cambium.
A cambium is lateral meristem, not intercalary. The extra stelar cambium, present outside the stele region is termed as cork cambium or phellogen. It is derived from pericycle (a primary permanent tissue) and produces cork or phellem towards the periphery and phelloderm or secondary cortex on inside, they are the extra stelar secondary tissues and are not part of annual growth rings.
Primary cambium or procambium is the embryonic tissues that give rise to primary vascular bundle; annual growth rings are formed by secondary vascular bundles.
Therefore, the correct answer is option A.
Polyarch and exarch vascular bundles are the characteristic of
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Dicot stem
0%
Dicot root
0%
Monocot stem
0%
Monocot root
Explanation
In monocot root, vascular bundles are radial in arrangement. There are eight bundles each of xylem and phloem. Hence, the condition is described as polyarch. Xylem is described as exarch.
Polyarch - Primary xylem of root with a large number of protoxylem strands. When protoxylem is pointing towards periphery, it is called as exarch xylem and when it is pointing towards the centre, it is called as endarch. So, polyarch and exarch vascular bundles are the characteristic of monocot root and not of dicot stem (endarch), dicot root (exarch) and monocot stem (endrach xylem).
Thus, the correct answer is option D.
Lysigenous cavity and Y-shaped xylem occurs in
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Dicot stem
0%
Monocot root
0%
Monocot stem
0%
Dicot root
Explanation
Lysigenous intercellular spaces is type of intercellular space arises through dissolution of entire cells, which are therefore called as lysigenous cavity. These cavities of intercellular spaces store up water, gases and essential oils in them. The examples are commonly found in water plants and many monocotyledonous stems. The secretory cavities in Eucalyptus,
Citrus
and
Gossypium
are good examples. In monocot stem the vascular bundle encloses both xylem and phloem. Xylem is found towards the inner surface and phloem towards the outer surface. Cambium is absent. Hence, the vascular bundles are described as conjoint, collateral and closed. In the xylem, there are two metaxylem and two protoxylem vessels arranged in the shape of Y.
Eustele is characteristic of
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Monocots
0%
Dicots
0%
Pteridophytes
0%
Bryophytes
Explanation
Eustele - In this arrangement, the primary vascular tissue consists of vascular bundles, usually in one or two rings around the pith. In addition to being found in stems, the eustele appears in the roots of monocot flowering plants. The vascular bundles in a eustele can be collateral with the phloem on only one side of the xylem or bicollateral with phloem on both sides of the xylem, as in some Solanaceae. So, eustele is the characteristic of monocots and absent in dicots, pteridophytes and bryophytes.
Thus, the correct answer is option A.
The layers of cells lying between endodermis and vascular bundle is
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Cortex
0%
Pith
0%
Pericycle
0%
Exodermis
Explanation
The layers of cells lying between endodermis and vascular bundle is pericycle. The pericycle is a cylinder of parenchyma or sclerenchyma cells that lies just inside the endodermis and is the outer most part of the stele of plants. Although it is composed of non-vascular parenchyma cells, it is still considered part of the vascular cylinder, because it arises from the procambium as do the vascular tissues it surrounds.
The hypodermis present in maize stem is
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0%
Parenchymatous
0%
Collenchymatous
0%
Sclerenchymatous
0%
Meristematic
Explanation
Parenchymatous cells are thin walled polyhedral, isodiametric living cells with sufficient cytoplasm and one or more nuclei. Collenchymatous cells have thick non lignified walls that provide mechanical support and tensile strength to the growing organs. Sclerenchymatous cell are thick walled dead lignified cells without any secretory function; these cells together with collenchyma makes major part of mechanical tissues of plant. Cell with ability to produce new cells are said to have meristematic activity and are termed as meristematic cells. Maize stem has single layered epidermis which is covered with well developed cuticle. It is followed by sclerenchymatous hypodermis which is 5-7 layers thick outer cortical region which in turn surrounds aerenchymatous ground tissues.
Therefore, the correct answer is option C.
Innumerable vascular bundles, lack of cambium and lack of a well demarcated pith is found in
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Sugarcane
0%
Sunflower
0%
Radish
0%
Pea
Hard bast (bundle cap) occurs in
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0%
Sunflower stem
0%
Wheat stem
0%
Sunflower root
0%
Both of (A) and (C)
Explanation
Hard bast is the patch of sclerenchyma present on outside of each vascular bundle, thereby forming a bundle cap over each bundle. They serve to provide additional mechanical support to the stem and are present in Sunflower stem. Wheat stem represent a monocot stem in which each vascular bundle is surrounded by thick walled bundle sheath, they do not have hard bust. Root is marked by presence of primary xylem and phloem in different radii, separated from each other.
Therefore, the correct answer is option A.
Cortex and pith are not distinguished in
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0%
Monocot stem
0%
Monocot root
0%
Dicot stem
0%
Dicot root
Explanation
The ground tissues in dicot stem are well differentiated into cortex, endodermis, pericycle and pith but are undifferentiated in monocot stem. Dicot stem has pith with thin walled parenchymatous cells but monocot stem lacks it. Primary dicot root has no or reduced pith, whereas a large pith, sometimes sclerenchymatous, is present in the monocot root.
Therefore, the correct answer is option A.
Extrastelar secondary growth takes place by
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0%
Vascular cambium
0%
Phellogen
0%
Phellem
0%
Phelloderm
Explanation
Intrafascicular cambium (present between xylem and phloem) and interfascicular cambium together form a complete cambium ring called as vascular cambium or just cambium. Vascular cambium exhibits two patterns of division; multiplicative divisions or additive divisions.
During secondary growth, rupturing of the
epidermal
cell and outer cortex by secondary tissues induces the
formation
of the
new
protective layer, periderm. Pericycle resumes the meristematic activity and divides to form cork cambium /phellogen. The cork cambium exhibit meristematic activity and produces cork /phellem towards the periphery and phelloderm on inside i.e.,
extra stellar
growth
So, the correct answer is '
Phellogen'
Wound meristem is
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Secondary meristem
0%
Inducible cambium
0%
Lateral meristem
0%
All of the above
Explanation
Wound meristem is produced by any permanent tissue, mostly epidermis, as a response to wound/injuries. The meristem, which is derived from a primary permanent tissue is termed as secondary meristem.
Wound meristem is present along the sides and serves as cork cambium to produce secondary extra stelar tissues, phelloderm and phellem, which in turn increase the girth of the plant part.
Meristem present at the sides of the plant is termed as lateral meristem, they are derived from primary permanent tissues during secondary growth and cause increase in girth of the plant, thus wound meristem is a lateral meristem. Wound meristem production is induced by injuries. It is not produced during normal secondary growth. So, it is an inducible meristem.
So, the correct answer is '
All of the above'
In the T.S. of a root,
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Protoxylem and metaxylem are not present on same radius
0%
Protoxylem is absent
0%
Protoxylem is towards inside and metaxylem is towards outside
0%
Metaxylem is towards inside and protoxylem towards outside
Explanation
Root is marked by presence of primary xylem and phloem in different radii, separated from each other while stem have them arranged side by side in same radius.
Root xylem is exarch xylem in which xylem formed first is present towards the periphery and is termed as protoxylem while metaxylem is present near the centre. Metaxylem is present towards inner side.
Thus, the correct answer is option D.
Four radial vascular bundles are found in
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Dicot root
0%
Monocot root
0%
Dicot stem
0%
Monocot stem
Explanation
Vascular bundles wherein xylem and phloem lie side by side are called as radial bundles, which are the characteristic feature of the root. A number of vascular bundles vary from 2-6 in dicot root, whereas monocot roots have numerous bundles, not limited to 6. So, four radial vascular bundles can be found in dicot root.
Both monocot and dicot stem have conjoint vascular bundles, wherein xylem and phloem are separated from one another.
So, the correct answer is option A.
What is the characteristics of a vascular bundle of monocot stem?
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Open and surrounded by a sclerenchymatous bundle sheath
0%
Closed and not surrounded by bundle sheath
0%
Closed and surrounded by bundle sheath
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Open and not surrounded by a bundle sheath
Explanation
In a monocot stem the vascular bundles are not arranged in a circle but are usually scattered throughout the ground tissue. There is no clearly defined pith as there is in many dicotyledonous species.
The vascular bundles of monocotylenous plants do not contain a layer of meristematic tissue (cambium) as the dicots do. Thus, no new cells can be formed inside the vascular bundles of monocots and their vascular bundles are termed as closed, whereas those of dicot plants are open. Bundle sheath is developed either partly or completely surrounding the vascular bundle. Thus, option C is correct.
Normally in dicot stems, phellogen develops from
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Hypodermis
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Phellem
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Endodermal cells
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Epidermal and pericycle cells
Explanation
Phellogen is the extrastelar lateral meristem that produces extrasteler secondary tissue system. Epidermis is the outermost covering of the primary stem that delimits cotex on outer side and is ruptured by stelar secondary growth, therefore cannot produce phellogen. Cortex is the ground tissue which surrounds the central stele and is derived from ground meristem. Hypodermis refers to 5-7 layers of cortical cells present just beneath the epidermis which resume the meristematic activity and produce phellogen just beneath the epidermis. The innermost layer of cortex forms endodermis while the phellogen is produced just beneath the epidermis. The outermost covering of stele forms pericycle it is an intrasteler tissues present in a stele which means that phellogen (extrastelar lateral meristem) cannot be produced by pericycle. The phellogen or cork cambium produces cork or phellem towards the periphery.
Therefore, the correct answer is option A.
Secondary growth in the cortical region of a dicot stem is due to the activity of
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Cambium
0%
Phellogen
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Phellem
0%
Phelloderm
Explanation
Vascular cambium is a lateral cambium which is produced by intrafascicular (present between xylem and phloem) and interfascicular cambium. Vascular cambium adds phloem or xylem mother cell that differentiates into their respective cell types, thus, it causes secondary stellar growth. Hypodermis, the cortical cells present just beneath the epidermis, resume the meristematic activity and produce phellogen just beneath the epidermis. Phellogen is the extrastelar lateral meristem that produces extrasteler secondary tissue system. The cork cambium or phellogen produces phelloderm on inside and phellem or cork on outside thereby adding extrastelar secondary tissues.
Therefore, the correct answer is option B.
In monocot stems, secondary growth cannot occur, because vascular bundles are
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0%
Scattered
0%
Open
0%
Closed
0%
Radial
Explanation
Secondary growth refers to the growth that results from cell division in the cambia or lateral meristems and that causes the stems and roots to thicken, while primary growth is growth that occurs as a result of cell division at the tips of stems and roots, causing them to elongate and gives rise to primary tissue.
In monocot stem vascular bundles are closed, because cambia is absent. So, secondary growth can not occur
So, the correct answer is '
Closed'
Which is not correct about heartwood?
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It is formed of living cells.
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It contains resins, tannin and other organic contents.
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It is of dark colour.
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It lies in the centre region.
Explanation
Heartwood is also called as 'duramen'. It is dead, central wood of trees. Its cells usually contain tannins or other substances that make it dark in colour and sometimes aromatic. Heartwood is mechanically strong, resistant to decay and less easily penetrated by wood-preservative chemicals than other types of wood.
Non-porous wood is found in which plants
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Dicots
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Monocots
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Gymnosperm
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Cactus
Explanation
As wood of angiosperms contains vessels, it is called porous wood. On the other hand, the wood of gymnosperms lacks vessels and is called nonporous wood. Gymnosperms are considered 'non-porous' because they lack vessel pores. Pines are typical examples of softwood. So, non-porous wood is found in gymnosperms and not in dicots, monocots or cactus.
So, the correct answer is option C.
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Practice Class 11 Medical Biology Quiz Questions and Answers
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