Ground tissues - class-XI

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. Parenchyma cells are living cells and may remain meristematic at maturity—meaning that they are capable of cell division if stimulated. They have thin and flexible cellulose cell walls, and are generally polyhedral when close-packed, but can be roughly spherical when isolated from their neighbours. They have large central vacuoles, which allow the cells to store and regulate ions, waste products, and water. Tissue specialised for food storage is commonly formed of parenchyma cells.

Laticiferous vessels are the specialized thin walled parenchymatous cells that secrete latex and are found in the cortex. They lack pits and are composed of cellulose and hemicelluloses and serve to secrete latex. 

Ground tissue includes all tissues except epidermis and vascular bundles. The ground tissue comprises the bulk of the primary plant body. Parenchyma, collenchyma and sclerenchyma cells are common in the ground tissue.

On the basis of location and function, three main tissue systems are found in plants, dermal, vascular, and ground tissue. Dermal tissue is composed of epidermal cells, closely packed cells that secrete a waxy cuticle that aids in the prevention of water loss. The primary components of vascular tissue are the xylem and phloem. The ground tissue of plants includes all tissues that are neither dermal nor vascular. The three types of ground tissue, parenchyma, collenchyma, and sclerenchyma, function in photosynthesis, storage, regeneration, support, and protection.

The ground tissue of plants includes all tissues that are neither dermal nor vascular. It can be divided into three types parenchyma, collenchyma, and sclerenchyma. Cortex is composed of thin-walled parenchymal cells. The pericycle is a cylinder of parenchyma or sclerenchyma cells that lies just inside the endodermis and is the outer most part of the style of plants.

Medullary ray is a band of parenchyma in the secondary xylem extending into the secondary phloem of the stems of certain vascular plants, formed by the cambium and helps for the storage of food and conduction of nutrients. it helps in the gaseous exchange through the intercellular spaces.

• The roots that arise horizontally from the primary roots which provide anchorage to the plants and fixes it into the soil. 
• These roots help in the uptake of water and nutrients from the soil which is required for the growth and development of the plants.
  
• They are endogenous in nature as it is developed from the cells of the pericycle which become meristematic and undergoes periclinal (parallel to the surface of a part) and anticlinal (right angles to the surface) division.
• So, the correct answer is 'Pericycle'.

• Passage cells are also known as transfusion cells.
• They are thin-walled cells which lack suberin and are found in the endodermis (is the central innermost layer of the cortex) of vascular plants (plants which consist of vascular tissues i.e, xylem and phloem).
• They are located opposite the protoxylem strands or elements.
• They are found in the endodermis of dicots.
• So, the correct answer is 'Protoxylem elements'.

The tissues present in a plant which are dermal nor vascular are called ground tissues.

• The ground tissues consist of the following:-

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.

Passage cells forms the endodermis of older roots of monocots. They are thin walled and have casparian strips, unlike the other cells that becomes suberized and waterproof. Passage cells function to allow transfer of solutes into the stele, in order to eventually reach the transpiration system.

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 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.

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.

Passage cells are endodermal cells of older roots which have retained thin walls and Casparian strips rather than becoming suberized and waterproof like the other cells around them, to continue to allow some symplastic flow to the inside (cortex to pericycle). 

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.

The endodermis is the central, innermost layer of cortex in some land plants. It is made of compact living cells surrounded by an outer ring of endodermal cells that are impregnated with hydrophobic substances (Casparian strip) to restrict apoplastic flow of water to the inside. The endodermis is the boundary between the cortex and the stele. 

In the stem, the pith and the cortex make up the ground tissue. The pith is located within the cylinder of vascular tissue, where it often exhibits a spongy texture because of the presence of large intercellular air spaces. If the growth of the pith fails to keep up with that of the surrounding tissues, the pith may degenerate, producing a hollow stem. In general, roots lack piths, although there are exceptions to this rule. 

Casparian strip is a band of cell wall material deposited on the radial and transverse walls of the endodermis. It is chemically different from the rest of the cell wall. 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. 

In plant anatomy, 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.

Casparian strip is a band of cell wall material deposited on the radial and tangential 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. It varies in width and is often much narrower than the wall in which it occurs. It is typically located closer to the inner tangential wall than the outer. 

Passage cells are endodermal cells of older roots, which have retained thin walls and Casparian strips rather than becoming suberized and waterproof like the other cells around them, to continue to allow some symplastic flow to the inside. Passage cells function to allow transfer of solutes, such as calcium and magnesium into the stele, in order to eventually reach the transpiration system. 

In the histogen theory Henstein divided the shoot apex into various zones. Each zone consists of a group of initial cells and called as histogen or a tissue builder.

Epidermis is the part of epidermal tissue system and forms the outer protective covering of primary plant body. 

The endodermis is the central, innermost layer of cortex in some land plants. It is made of compact living cells surrounded by an outer ring of endodermal cells that are impregnated with hydrophobic substances (Casparian Strip) to restrict apoplastic flow of water to the inside. The endodermis is the boundary between the cortex and the stele. In many seedless vascular plants, the endodermis is a distinctly visible layer of cells immediately outside the vascular cylinder (stele) in roots and shoots. In most seed plants, especially woody types, an endodermis is absent from the stems but is present in roots. 

Histogen theory by Hanstein states that shoot apical meristem consists of three distinct zones- 

Protostele is the most primitive type of stele with central xylem surrounded by phloem and pericycle. Pith is absent in them. Medullation (appearance of pith) of a protostele with central pith is called as siphonostele and thus has central pith surrounded by xylem, phloem and pericycle. Separation of vascular strands by parenchyma in siphonostele give rise to eustele. Thus, the correct answer is option B.

A. Dicot leaf – Mesophyll is the ground tissue. It is differentiated into palisade and spongy parenchyma.

B. Monocot leaf – Mesophyll is the ground tissue. It is not differentiated. It shows only spongy parenchyma.

C. Cortex is the ground tissue in dicot stem. It is differentiated into hypodermis, general cortex and endodermis.

D. Monocot stem – the region present inner to the hypodermis is ground tissue. It shows scattered arrangement of vascular bundles.

So, the correct option is ‘Dicot stem’.

The cortical region present below epidermis is called ‘ Hypodermis’. It is made up of collenchyma in dicotyledons and sclerenchyma in monocotyledons.

So,
the correct option is ‘Collenchyma’.

A. The hypodermis is sclerenchymatous, vascular bundles are closed, phloem parenchyma is absent – True in. monocot stem.

B. The hypodermis is sclerenchymatous, vascular bundles are open, phloem parenchyma is absent – False because vascular bundles are closed in monocot stem.

C. Hypodermis is collenchymatous, vascular bundles are closed, phloem parenchyma is present – false, because hypodermis is sclerenchymatous and phloem parenchyma is absent in monocot stem

D. Hypodermis is sclerenchymatous, vascular bundles are closed, phloem parenchyma is present – false, because, phloem parenchyma is absent in monocot stem.

So, the correct option is ‘Hypodermis is sclerenchymatous, vascular bundles are closed, phloem parenchyma is absent’.

In internal structure of root and dicot stem, the region appears between epidermis and stele is cortex. In roots, cortex includes general cortex and endodermis, where as in dicot stems, cortex includes, hypodermis, general cortex and endodermis. In roots, cortex is concerned in the radial conduction of water, where as in dicot stems, it is concerned in the storage of food materials.

So, the
correct option is ‘Epidermis and stele’.

• The secondary cortex which is also known as phelloderm is produced by phellogen or cork cambium. 
• The cork cambium or the phellogen is a lateral meristem which is responsible for the formation of periderm.
  
• The cells of the periderm which grows inward are known as phelloderm while the cells that grow outward is known as phellem or cork.
• The periderm layer has three distinct layers:-

Ground tissue of plants consists of all tissues except epidermis and vascular tissues. It is divided into three types based on the nature of the cell walls. These are parenchyma, collenchyma and sclerenchyma. 

The ground tissue consists  majorly of parenchymatous tissue that forms the whole plant body other than the epidermis and the vascular bundles. It arises from the periblem meristematic tissue.

Ground tissue (fundamental tissue) consists of the cortex, endodermis, pericycle, and pith. Phloem is part of the vascular tissue system, not the ground tissue system.

The tissues that are involved in the secretion of gums, resins, volatile oils, nectar and latex are known as secretory tissues. These are further differentiated into glandular and laticiferous. Glandular tissue consists of special structures or glands made up of isolated cells or small group cells with granular cytoplasm filling it and with a large nucleus. Thus, the correct answer is option C.

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. As in the dicots the xylem of the bundles is pre-orientated toward the middles of the stem. Maize is a monocot. So, the vascular bundles in maize stem are scattered in ground tissue. 

Stoma (plural stomata) is a pore, found in the epidermis of leaves, stems and other organs that is used to control gas exchange. The pore is bordered by a pair of specialized parenchyma cells known as guard cells that are responsible for regulating the size of the opening. Stomata is absent in cork or phellem. A lenticel is a porous tissue consisting of cells with large intercellular spaces in the periderm of the secondarily thickened organs and the bark of woody stems and roots of dicotyledonous flowering plants. It functions as a pore, providing a pathway for the direct exchange of gases between the internal tissues and atmosphere through the bark, which is otherwise impermeable to gases. Cork contains lenticels. Thus, option A is correct. Passage cells are endodermal cells of older roots which have retained thin walls and Casparian strips rather than becoming suberized and waterproof like the other cells around them, to continue to allow some symplastic flow to the inside. Experimental evidence suggests that passage cells function to allow transfer of solutes such as calcium and magnesium into the stele, in order to eventually reach the transpiration system. Sieve tube elements lacks nuclei. Quiescent zone is present in root apex. 

A. Dermal tissue system – Epidermis 

B. Vascular tissue system – Xylem and phloem 

C. Ground tissue system – General cortex, endodermis, pericycle,medulla,      medullary rays, conjunctive tissue, mesophyll 

D. Epidermal tissue system – Epidermis

So, the correct option is ‘Ground tissue system’.

A. Medulla – central part of the stele.

B. Stele – central part of the root and dicot stem, includes pericycle, vascular bundles, medulla, medullary rays or conjuctive tissue.

C. Cortex – middle part of the dicot stem and root, includes hypodermis, general cortex and endodermis.

D. Exodermis – outer part of mature monocot root.

So, the correct option is ‘Cortex’.

A.Endodermis - Inner most layer of cortex

B.Epidermis – outer layer of organs.

C.Exodermis – outer most layer of mature monocot root.

D.Hypodermis – it is present inner to the epidermis in stems.

So, the correct option is ‘Endodermis’.

Stele in which vascular bundles are arranged in scattered manner in the ground tissue, is called Atactostele. It is found in monocot stem.

In the anatomy or internal structure of dicot stem, epidermis, followed by cortex, followed by endodermis, pericycle, phloem, xylem, medulla are present from outer to inner.

Cork cambium arises from outer most layer of the cortex which is the ground tissue. 

Grafting is a technique whereby tissues from one plant are placed or inserted into another in such a way that the vascular tissues of both the plants may join together. The plant which is selected for its roots is called as the stock and the one selected for its stems and leaves and flowers is called as the scion. For successful grafts, the events that should take place is the production of the callus tissue between the cells of the stock and scion.