Internal structure of monocot stem - class-X

Xylem comprises of vessels, tracheids, xylem parenchyma, and restricted xylem strands.  the vessel is Y-molded with bigger two round set metaxylem vessels shaping the arms and littler yearly or winding protoxylem vessels, framing the base.

Vascular tissue system composed of vascular bundles and they are scattered. So, the steles are called atactostele. Hypodermis is multilayered and sclerenchymatous. Endodermis is not developed.

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 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.

Anatomy of the monocot stem shows that while the vascular bundles are oval in shape, numerous and scattered, it is by nature, conjoint, collateral, closed and endarch without any lysigenous activity.

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. 

Monocot stem vascular bundles are found irregularly scattered in the ground tissue. Towards the periphery, the bundles are smaller in size while towards the centre, they are larger in size. The smaller bundles are younger, while the larger ones are older. Hence, the arrangement is described as centrifugal. 

Monocot stem vascular bundles are found irregularly scattered in the ground tissue. Towards the periphery, the bundles are smaller in size while towards the centre, they are larger in size. The smaller bundles are younger, while the larger ones are older. Hence, the arrangement is described as centrifugal or endarch. 

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 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. 

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. 

Secondary growth is increase in the circumference / girth of the plant organs due to the formation of secondary tissues in stelar and extra stelar regions. Normally secondary growth takes place in roots and stem of dicotyledons and gymnosperms. Due to lack of cambium in monocotyledons, secondary growth is absent. But exceptionally, secondary growth takes place in some monocotyledons, such as palm, Yucca, Dracaena etc. 

In monocot stem vascular bundles are found irregularly scattered in the ground tissue. Towards the periphery, the bundles are smaller in size, while towards the centre, they are larger in size. The smaller bundles are younger, while the larger ones are older. Hence, the arrangement is described as centrifugal. 

Atactostele is a type of eustele, found in monocots, in which the vascular tissue in the stem exists as scattered bundles. Most seed plant stems possess a vascular arrangement, which has been interpreted as a derived siphonostele and is called as eustele. There is also a variant on the eustele found in monocots, like maize and rye. The variation has numerous scattered bundles in the stem and is called as an atactostele.

In the monocots, the vascular bundles are of the collateral and closed type. The closed vascular bundles lack the cambium and cannot show secondary growth. In the stem, vascular bundles are found scattered in the ground tissue. They are more in number at the periphery as compared to the centre. In the monocot roots, the vascular bundles are closed type an found in the stele.

In monocot stem, all the vascular bundles, the xylem and phloem are in the same line; cambium is absent; phloem is external to xylem; protoxylem faces the centre. Hence, the vascular bundles are described as conjoint, collateral, endarch and closed.  

The region present below the epidermis in monocot stem is hypodermis. It is composed with sclerenchyma. Sclerenchyma is dead mechanical tissue. It provides mechanical strength to the stem.

So, the correct option is 'Sclerenchyma’.

In monocot stem, the endodermis is absent. It has a single layer epidermis. The vascular bundles are scattered.

A.Sunflower – Ground tissue is differentiated into hypodermis, general cortex and endodermis, pericycle, medulla and medullary rays.

B.Pisum - Ground tissue is differentiated into hypodermis, general cortex and endodermis, pericycle, medulla and medullary rays.

C.Maize – Ground tissue is undifferentiated.

D.Cucurbita - Ground tissue is differentiated into hypodermis, general cortex and endodermis, pericycle, medulla and medullary rays.

So,
the correct option is ‘Maize’.

Secondary growth does not take place in monocotyledons, because of the absence of cambium between xylem and phloem in vascular bundles. These vascular bundles are called closed vascular bundles.

So, the correct option is ‘Closed’.

In monocot stem, cambium is absent in the vascular bundles. Due to this, grafting is not possible in monocot stem

So, the correct answer is ‘Lack cambium’

A.Monocot stem - conjoint, closed vascular bundles are present, in which phloem parenchyma is absent in the phloem.

The anatomy of monocot stem shows outer single layered epidermis with cuticle and stomata, sclerenchymatous hypodermis, large, wide parenchymatous ground tissue. In this vascular bundles are scatteredly arranged. So the stele is called Atactostele. Vascular bundles are outerly surrounded by sclerenchymatous fibres. So they are called fibrovascular bundles and are collateral, conjoint, closed with endarch xylem. Protoxylem lacuna is present. General cortex, endodermis, pericycle, medulla and medullary rays are absent.

So, the correct option is ‘Starch sheath’.

The stele is the central part of the root and stem which contains tissues derived from the procambium, in monocots, the vascular bundles are scattered and the stele is an atactostele.

The Y-shaped arrangement of xylem vessels is found in monocot stem, two metaxylem vessels are located at the upper two arms, while the base or the stick of the letter consists of one or two protoxylem vessels.

In monocot stem (Maize), the xylem appears Y shaped. The lowermost or innermost protoxylem undergoes disintegration to produce lysigenous cavities also called the protoxylem lacuna.

In a monocot stem (Example Maize), the stem is differentiated into Epidermis, hypodermis and ground tissue. In the ground tissue are embedded vascular bundles that are conjoint, colateral and closed.The vascular bundles are not enclosed by endodermis and pericycle.

Stems of monocots do not have lateral or secondary cambium. Roots of both monocots and dicots do not have secondary or lateral cambium. Hence, true secondary growth does not occur in stems and roots of monocots. But, in some exceptional cases if secondary growth takes place due to dedifferentiation of tissue cells of the cortex, pericycle etc into meristematic tissue this type of secondary growth is called anomalous secondary growth.

The first xylem formed is called as protoxylem. Protoxylem is later torn apart and a cavity is formed. The entire protoxylem is dissolved hence, such cavity is called as lysigenous cavity. The protoxylem shows an empty space, called as 'lacuna'. 

Monocot stem vascular bundles are found irregularly scattered in the ground tissue. 

Monocot stem vascular bundles are found irregularly scattered in the ground tissue. Towards the periphery, the bundles are smaller in size while towards the centre, they are larger in size. The smaller bundles are younger, while the larger ones are older. Hence, the arrangement is described as endarch. 

Monocot stems, in which the stele consists of many vascular bundles in a complex arrangement, are said to have an atactostele. 

Date palm is a monocot and lack lateral meristem; the meristem present along the sides causing the increase in girth of the plant. 

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. 

In monocot stem, cortex is not differentiated into hypodermis, general cortex and endodermis. In the place of cortex a large, wide region is present called Ground tissue is present. It is parenchymatous, stores water and food materials. In this vascular bundles are present scatteredly.

So,
the correct option is ‘monocot stem’

A.Monocot leaf – vascular bundles are covered by parenchymatous bundle sheath.

B. Monocot stem – vascular bundles are covered by sclerenchymatous fibres. So these are called fibrovascular bundles.

C. Monocot root – there is no any covering around the vascular bundles.

D. Dicot stem – there is no any covering around the vascular bundles.

So, the correct option is ‘Monocot stem’.

A.Dicot root – phloem parenchyma is present.

B.Dicot leaf – Phloem parenchyma is present.

C.Monocot stem – phloem parenchyma is absent.

D.Dicot stem – Phloem parenchyma is present.

So, the correct answer is 'Monocot stem'.

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In the anatomy of monocot stem, epidermis, hypodermis, general cortex, ground tissue and vascular bundles are present. Cortex is differentiated into hypodermis, general cortex, endodermis and stele is not differentiated into pericycle, vascular bundles, medulla and medullary rays.So, the correct option is ‘Indistinguishable’.

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A.Dicot stem – collateral, conjoint, endarch, open vascular bundles present in the form of rings.

B.Monocot stem – collateral, cojoint, endarch, closed vascular bundles present in the form of scattered manner in a ground tissue.

C.Dicot root – radial vascular bundles are present.

D.Monocot root – radial vascular bundles are present.

So, the correct option is ‘Monocot stem’.

I.Conjoint – applicable – because xylem and phloem are present side by side in the vascular bundles.

II.Endarch protoxylem – applicable – because protoxylem is present towards medulla side and metaxylem is present towards the pericycle side.

III.Open – not applicable – because, cambium is absent between the xylem and phloem in the vascular bundles.

IV.Phloem parenchyma is absent – applicable – in the phloem of monocots phloem parenchyma is not present.

So,
the correct option is ‘III’

A.Bicollateral closed vascular bundles – Not present in any plants

B.Bicollateral open vascular bundles – found in the stems of Cucurbitaceae members

C.Collateral open vascular bundles – found in the dicotyledonous stems.

D.Collateral closed vascular bundles – found in the monocotyledonous stems.

So, the correct option is ‘Collateral closed vascular bundles’.

In monocot stem, epidermis, hypodermis, ground tissue, and vascular bundles are present. General cortex, endodermis, pericycle, medulla, medullary are absent. In the phloem, phloem parenchyma is also absent. Xylem and phloem are present on same radii, and also present side by side. So they are also called Collateral and Conjoint vascular bundles. In the vascular bundles, cambium is absent between xylem and phloem, So these are closed vascular bundles. In the xylem, protoxylem is towards the centre, and metaxylem is towards the periphery. So, it is an endarch xylem. 

The monocot stem shows the following characteristics: 

In monocot stems, the vascular bundles are dispersed. In dicot stems, the vascular bundles are arranged in ring.

Monocot plants, as the name suggests have only one cotyledon. these plants have characteristic features like fibrous root system because the radicle is short-lived, thus replaced by adventitious roots. They also have parallel-veined leaves and trimerous flowers.