Samacheer Class 11 Bio Botany - Tissue and Tissue System

1. Sclereids – dead cells Isodiametric – but some elongated.
2. Cell wall is very thick due to lignification
3. Lumen – much reduced
4. Pits – may be simple or branched.

Sieve tubes are long tube-like conducting elements in the phloem. These are formed from a series of cells called sieve tube elements. The sieve tube elements are arranged one above the other and form vertical sieve tube. The end wall contains a number of pores and it looks like a sieve. So it is called as sieve plate. The sieve elements show nacreous thickenings on their lateral walls. They may possess simple or compound sieve plates.
The function of sieve tubes are believed to be controlled by campanion cells In mature sieve tube, Nucleus is absent. It contains a lining layer of cytoplasm. A special protein (P. Protein = Phloem Protein) called slime body is seen in it. In mature sieve tubes, the pores in the sieve plate are blocked by a substance called callose (callose plug). The conduction of food material takes lace through cytoplasmic strands. Sieve tubes occur only in Angiosperms.

Characters
Dicot root
Monocot root
1. Pericycle
Gives rise to lateral roots, phellogen and a part of vascular cambium
Gives rise to lateral roots only.
2. Vascular tissue
Usually limited number of xylem and phloem strips.
Usually more number of xylem and phloem strips,
3. Conjunctive tissue
Parenchymatous; Its cells are differentiated into vascular cambium.
Mostly sclerenchymatous but sometimes parenchymatous. It is never differentiated in to vascular cambium.
4. Cambium
It appears as a secondary meristem at the time of secondary growth.
It is altogether absent.
5. Xylem
Usually tetrach
Usually poly arch
6. Pith
Absent
Present at the centre

Characters
Dicot root
Monocot root
1. Hypodermis
collenchymatous
Sclerenchymatous
2. Ground tissue
Differentiated into cortex, endodermis and pericycle and pith
Not differentiated, but it is a continuous mass of parenchyma.
3. StarchSheath
Present
Absent
4. Medullary rays
Present
Absent
5. Vascular bundles
a) Collateral and open
a) Collateral and closed
b) Arranged in a ring
b) Scattered in ground tissue
c) Secondary growth occurs
c) Secondary growth usually does not occur.
Part-II
11th Bio Botany Guide Tissue and Tissue System Additional Important Questions and Answers
I. Choose the correct answer

b) False – True – False – True
IV. With Reference To The Given Diagram, Identify The Incorrect Option Given Below:

:
Sclerenchyma is the tissue found in these fruits
A – Pear fruit
B – Strawberry
C – Guava

C. C → E → A → D → B
VII. From the given choose the correct answer – Regarding Assertion & Reason

• The organisation of cells and different kinds of tissues is understood.
• It is studied by means of dissection and microscopic examination.
• The organisation of cells and different kinds of tissues is understood by the study of anatomy
• The anatomical structure of different organs of plants can be compared
• The anatomical knowledge play an important role in taxonomical studies too.

The pulp of pear has Brachysclereids that make it stony and gritty, whereas the seed Coat of Peas seed coat is bony and shiny due to the presence of Osteosclereids

Centrach
Mesarch
Protoxylem lies in the centre, surrounded by metaxylem
Protoxylem lies in the centre, surrounded by metaxylem
Only one Vascular stand is developed
Eg – Selaginella sp
Here unlike cent reach many vascular bundles are developed
Eg – Ophioglossum sp.

Trichoblast
Trichomes
The root epidermis is made up of single layer of parenchyma, with big and small cells – The root hair are the extension of small cells known as trichoblast.
The epidermal layers of stems and leaves have unicellular or multicellular appendages that originate from the epidermal cells, known as trichomes, can be branched or unbranched, glandular or non glandular, helpful m dispersal of fruits & seeds. They are also protective infunction.

Exarch
Endarch
Protoxylem lies towards the periphery and metaxylem towards the centre is called Exarch condition.
Eg. – Root Anatomy
Protoxylem lies towards the centre and metaxylem, towards the periphery is known as Endarch condition.
Eg. Stem Anatomy

• In Monoeoi stem, Xylem vessels occur in the form of letter ‘ Y’. The upper two arms of has two metaxylem vessels and at the base on or two protoxylem vessels occur.
• At maturity, the lowes, basal protoxylem disintegrates and form a cavity known as Protoxylem lacuna.

Eustele
Atactostele
Vascular bundles are arranged in the form of a ring around the pith is known as Eustele
Eg. Dicot Stem (Sun flower)
Vascular bundles are simply scattered in the ground tissue. This condition is known as Atactostele
Eg. Monocot Stem (Maize)

These fibres are present in the phloem. Natural Bast fibres are strong and cellulosic. Fibres obtaining from the phloem or outer bark of jute, kenaf, flax and hemp plants. The so-called pericyclic fibres are actually phloem fibres.

• The apparently inactive centre in the root anatomy, located between root cap and differentiating cells of the root.
• It is the site of hormone synthesis and also the ultimate source of all meristematic cells of the meristem.

Xylary fibres
Bast fibres
Associated with sec xylem tissue
Present in phloem
Derived from the vascular cambium
Derived from phloem or outer bark
Many types
Eg. Teak
Eg. Jute, Kenaf, Flax & hemp plant fibres

Some cells of the upper epidermis (eg: Grasses) are larger and thin-walled. They are called bulliform cells or motor cells. These cells are helpful for the rolling and unrolling of the leaf according to the weather change.

Proto & Metaxylem
Proto & Metaphloem
From the primary Xylem derived from procambium, the first formed elements are known as protoxylem and the later formed are known as metaxylem.
From the primary phloem derived from procambium, the first formed elements are known as proto phloem are known as meta phloem.

Bundle sheath of stem
Bundle sheath of leaf
1. Bundle sheath is the surrounding tissue of the vascular bundle
1. The sheath surrounding the dicot leaf and monocot leaf is known as bundle sheath
2. In monocot stem it is sclerenchymatous
2. It is parenchymatous both in Dicot and Monocot leaf
3. It is protective in function.
3.It is also known as border parenchyma, protective in function.

Guard Cells
Subsidiary Cells
1. The two kidney-shaped cells in dicot leat and the two dumbbell-shaped cells in monocot leaf, which flank the stoma are called Guard Cells
1. These are specialised epidermal cells, distinct from other cells of the epidermis
2. Chloroplasts are present in the cells
2. Chloroplasts are absent in the cells
3.Help in opening and closing of stoma
3.She subsidiary ceils assist guard cells in the opening and closing of stoma

Radial
Collateral
1. Here, the xylem and phloem are arranged at different radius, (i.e) alternating with one another.
Eg. Root Anatomy
1. this condition, the phloem and xylem lie in the same radius, one below another.
2. Here phloem is above and xylem lies below, this condition is known as conjoint, collateral Eg. Stem Anatomy

• Plants adapted to grow in salty environmental conditions are known as Halophytes
• The secretion of ions by the salt glands, present in the leaves is the best mechanism to regulate the salt content of plant shoots.
• Eg. Mangrove Plants-Avicennia

• Main function is to provide mechanical strength.
• Grittiness in the pulp of fruits like Guava, the presence of Pear, Pyrus etc is due to the presence of Sclerenchyma tissue.
• Provide rough and stiffness to seed coats nuts etc.
• Give various types of commercially useful fibres. Eg. Jute, hemp, cotton.

A hydathode is a type of epidermal pore, commonly found in higher plants. Structurally, hydathodes are modified stomata, usually located at leaf tips or margins, especially at the teeth. Hydathodes occur in the leaves of submerged aquatic plants such as ranunculus fluitans as well as in many herbaceous land plants.

• In some leaves the upper and lower epidermis remain multilayered.
• The outer most layer has cuticle.
• In Nerium these multilayers and the culicle help to reduce the rate of transpiration.
• In Ficus the upper epidermal layer contain cystoliths made up of calcium carbonate crystals.
• These are plants that grow in dry climatic conditions and these are the Anatomical adaptations seen in xerophytic plants.

• In the Dicot stem, Dicot root and Monocot root the central part is made up of ground tissue known as pith.
• Usually, starch, fatty substances, tannin, phenol, calcium oxalate crystals are stored in the pith.
• Function: storage

• The theory was proposed by A. Schmidt (1924)
• There are two zones of tissues are found in apical meristem.
• Tunica-It is the peripheral zone of shoot apex that forms epidermis.
• Corpus – It is the inner zone of shoot apex that forms cortex and stele of the shoot.

• The Korper Kappe theory was proposed by schuepp.
• This theory is equivalent to Tunica corpus theory of shoot apex.
• The two divisions are distinguished by the type of T division.
• Korper is characterised by inverted T divisions
• Kappe is characterised by straight T divisions.

* Xylary fibres are associated with the secondary xylem tissue.
* These fibres are derived from the vascular cambium.
There are 4 types of xylary fibres.
* Libriform fibres – Long, narrow fibres with simple pits and lignified secondary walls
* Fibre tracheids – Shorter with moderate thickening pits-simple or bordered
* Septate fibres – Fibres have thin septa separating the lumen in to distinct chambers. Eg. Teak.
* Gelatinous fibres – Fibres with less lignin and more cellulose in the cell wall.

Xylem vessels are perforated at the end walls.
If the entire cell wall is dissolved – and, give rise one pore then it is known as single perforation plate. Eg. Mangifera.
If the perforation plate has many pores it is called Multiple perforation plate. Eg. Liriodendron.

* Proposed by Nagel
* Single apical cell-composes the Root meristem
* The apical initial is tetrahedral in shape and produces the root cap from one side.
* The remaining 3 sides produces epidermis cortex and vascular tissue.
* Fg. Vascular cryptogams.
IX. Identify the diagram & Label the parts.

These are the two types of Parenchyma tissue
Prosenchyma:
Here the parenchyma cells become elongated, pointed and slightly thick-walled it provide mechanical support
Chiorenchyma:
Parenchyma cells with chiorephyll is known as chiorenchyma.
Eg. Mesophyll of leaves. it can be divided in Palisade tissue and spongy tissue in dicot leaf.

Fibre
Sclereids
1. Long Cells
Short Cells
2. Narrow, Elongated pointed ends
Usually short and broad
3. Occurs in bundles
Occurs individually or in small groups
4. Commonly unbranched
Maybe branched
5. Derived directly from meristematic tissue
Develops from secondary sclerosis parenchyma cells

Quiescent centre concept was proposed by Clowes (1961) to explain root apical meristem activity. This centre is located between the root cap and differentiating cells of the roots. The apparently inactive region of cells in root promeristem is called quiescent centre. It is the site of hormone synthesis and also the ultimate source of all meristematic cells of the meristem.

Meristematic tissue
Permanent tissue
1. Cells divide repeatedly
1. Do not divide
2. Cells are undifferentiated
2. Cells are fully differentiated
3. Cells are small and Isodiametric
3. Ceils are variable in shape and size
4. Intercellular spaces are absent
4. Intercellular spaces are present
5. Vacuoles are absent
5. Vacuoles are present
6.Cell walls are thin
6.Cell walls are may be thick or thin
7. Inorganic inclusions are absent
7. Inorganic inclusions are present

Dicot Leaf
Monocot Leaf
1. Dorsiventral leaf
1. Isobilateral leaf
2. The mesophyll is differentiated into palisade and spongy parenchyma
2. Palisade parenchyma is present on both sides of the leaf and spongy parenchyma lies in the centre
3. Eg. Sunflower
3. Eg. Grass

Stomata are minute pores surrounded by two guard cells. The stomata occur mainly in the epidermis of leaves. In some plants addition to guard cells, specialised epidermal cells are present which are distinct from other epidermal cells. They are called Subsidiary cells. Based on the number and arrangement of subsidiary cells around the guard cells, the various types of stomata are recognized, The guard cells and subsidiary cells help in the opening and closing of stomata during gaseous exchange and transpiration.

Bulliform or motor cells
Silica cells
1. Some cells of upper epidermis in Grasses are larger and thin-walled, are known as bulliform or motor cells
1. Some of the epidermal cells of grass are filled with silica. They are called silica cells.
2. These cells are helpful for the rolling and unrolling of the leaf- according to the weather change in order to check transpiration
2. They provide mechanical stability and protection to the tissues

The outermost layer of the root is known as piliferous layer. It consists of single row of thin-walled parenchymatous cells without any intercellular space. Epidermal pores and cuticle are absent in the piliferous layer. Root hairs that are found in the piliferous layer are always unicellular. They absorb waer and mineral salt from the soil. Root hairs are generally short-lived. The main function of piliferous layer is protection of the inner tissues.

Sieve tube
Vessels
1. It is a component of phloem
1. It is a component of xylem
2. It is a syncyte (i.e) cell which is formed by fusion of cells is called syncyte
2. It is also a syncyte
3. Nucleus is absent but contain a lining layer of cytoplasm so known as living syncyte
3. Nucleus is absent but contain a lining layer of cytoplasm so known as living syncyte

The above two come under concentric type of vascular bundle. Here xylem and phloem are present in concentric circles one around the other, in some stems.
Amphicribral – (Halocentric)
Here xylem lies in the centre and phloem surrounding it.
Eg. Ferns – (Polypodium) dicots – aquatic Amphivasal – (Leptocentric)
Here phloem lies in the centre and xylem surrounding it.
Eg. Dragon plant – Dracena & Yucca

Dicot roots
Monocot root
1. Vascular tissue
Usually limited number of xylem and phloem strips
Usually more number of xylem and phloem strips.
2. Conjunctive tissue
Parenchymatous; Its cells are differentiated into vascular cambium
Mostly sclerenchymatous but sometimes parenchymatous. It is never differentiated in to vascular cambium
3. Cambium
It appears as a secondary meristem at the time of secondary growth
It is altogether absent
4. Xylem
Usually tetrarch
Usually poly arch

* In C 4 plants like maize, the tissue outside the vein, (vascular bundle), the bundle sheath is with large chloro- plasts where as its spongy tissue have few if any chloroplast.
* This anatomical uniqueness is known as Kranz anatomy. The border parenchyma has chloro plasts with out grana.
This kranz sheath help in efficient CO 2, fixation in C 4 plants than C 3 plants.

Primary phloem lies towards the periphery. It consists of protpphloem and metaphloem. Phloem consists of sieve tubes, companion cells and phloem parenchyma. Phloem fibres are absent in primary phloem. Phloem conduct organic foods material from the leaves to other parts of the plant body.
XI. 5 Marks Questions

1. Vascular bundles: Vascular bundles are scattered (atactostele) in the parenchyma ground tissue. Each vascular bundle is surrounded by a sheath of sclerenchymatous fibres called bundle sheath. The vascular bundles are conjoint, collateral, endarch and closed. Vascular bundles are numerous, small and closely arranged in the peripheral portion. Towards the centre, the bundles are comparatively large in size and loosely arranged. Vascular bundles are skull or oval-shaped.
2. Phloem: The phloem in the monocot stem consists of sieve tubes and companion cells. Phloem parenchyma and phloem fibres are absent. It can be distinguished into an outer crushed protophloem and an inner metaphloem.
3. Xylem: Xylem vessels are arranged in the form of ‘Y’ the two metaxylem vessels at the base. In a mature bundle, the lowest protowylem disintegrates and forms a cavity known as protoxylem lacuna.

• Schuepp (1917)- proposed it
• According to it, Root system has 2 zones – Korper and Kappe
• Korper – zone forms body and Kappe forms the cap
• This theory is comparable to Tunica – corpus theory of shoot apex.

• Sieve tubes are long tubes formed by a series of cells known as sieve tube elements.
• Arranged one above another to form vertical sieve tube.
• No. of pores occur on end walls – known as sieve plate.
• Sieve plates may be simple or compound.
• Sieve elements show nacreous thickening on their lateral walls.
• Mature sieve tube, nucleus is absent, only lining layer of cyto plasm, a special phloem protein (slimy body) is seen in it.
• Mature sieve tubes pores blocked by a substance known as callose (callose plug) sieve tube function as food conducting tissue Angiosperm.

Characters
Root
Stem
1. Epidermis
Absence of Cuticle and epidermal pores.
Presence of cuticle and epidermal pores.
Presence of unicellular root hairs.
Presence of unicellular and multicellular trichomes.
2. Outer cortical cells
Chlorenchyma absent
Chlorenchyma present
3. Endodermis
Well defined
ill-defined or absent
4. Vascular bundles
Radial arrangement
Conjoint arrangement
5. Xylem
Exarch
Endarch

Types/characters
Epidermal tissue system
Ground or fundamental tissue system
Vascular or conduction tissue system
1.Formation
Forms the outermost covering protoderm
Forms the ground meristem
Forms the procambial bundles
2. Components
epidermal cells, stomata and epidemic outgrowth
Simple permanent tissues – Parenchyma and Collenchyma
Xylem and Phloem
3.Functions
Protection of plant body; absorption of water in roots; gas exchange for photosynthesis and respiration; transpiration in shoots
Gives mechanical
support to the organs;
prepares and stores food
in leaf and stem
Conducts is water and food: gives mechanical strength

Characters
Dicot stem
Monocot stem
1. Hypodermis
Collenchymatous
Sclerenchymatous
2. Ground tissue
Differentiated into cortex, endodermis, and peri cycle and pith
Not differentiated but it is a continuous mass of parenchyma
3. Starch sheath
Present
Absent
4. Medullary rays
Present
Absent
5. Vascular bundles
a. Collateral and open
b. Arranged in a ring
c. Secondary growth occurs
a. Collateral and closed
b. Scattered in ground tissue
c. Secondary growth usually does not occur

The transverse section shows the following structure.
Piliferous layer or Epiblemma or Rhizodermis;
* Single-layer of parenchyma cells compactly arranged with out inter cellular space, devoid of circle and stomata (epidermal pores)
* Single called root hairs arise from the small cell known as trichoblast
Function: Protection & absorption
Cortex:
* Made of loosely arranged parenchyma cells with intercellular spaces.
* Starch grains are stored in, them leucoplasts occur in the cells.
Endodermis:
* Inner most layer of cortex – made up of single layer of barrel-shaped parenchyma cells.
* The radial and inner tangential walls have suberin and lignin thickening known as Casparian thickening.
* The cells opposite to protoxylem do not have Casparian thickening, known as Passage cells, which allow water to pass through but not the cells with Casparian thickening.
Stele:
All the tissue present inside endodermis comprise the stele, include pericycle & vascular bundle,
a) Pericycle:
Outer most layer of stele Single layer of parenchyma. The lateral roots originate from pericycle, so known to have endogenous origin.
Vascular bundle:
Made up of xylem and phloem.
Radial arrangement: In dicot root xylem and phloem are in different radii known as radial arrangement.
Exarch condition:
The protoxylem is pointing towards the periphery.
Tetrarch:
There are four protoxylem points, present this condition is known as tetrarch. Conjunctive tissue: The parenchyma tissue that separates xylem and phloem are known tissue.
Metaxylem – Vessels: are generally polygonal in cross-section.
Pith or Medulla: absent.

• Vascular bundles are skull-shaped, numerous, bigger bundles towards the centre and numerous small bundles arranged in the periphery.
• Vascular bundles are scattered in the parenchymatous ground tissue. This condition is known as Atactostele.
• V – Bs Conjoint Collateral, Closed and Endarch in nature
• Pith or Medulla is absent.

Epidermis:
A single layer of compactly arranged rectangular parenchymatous cells, with out intercellular space. Cuticle: on the outer walls check transpiration
Stomata: may be present here and their Chloroplasts: usually absent Multicellular hairs: occur in large numbers Function: Protective Cortex:
Lies below epidermis has 3 zones
1. Hypodermis:
Epidemial hay Made upof few layers of colknchyma cells liv- Cuticleing with thickenings at the successive tangential Epidenms avers giving mechanical inheiweeit
2. Chloresrchma:
A few layers below hypodermis with resin ducts in between
3. Parenchyma:
3rd zone, store food material.
Lndodermis or Starch Sheath:
inner most layer of cortex. barrel-shaped cells compactly managed without intercellular spaces.
Since starch grains are abundant in it. It is also a Medullary ray known as starch sheath, homologous to endodermis of root.
Stete: fonn a central ring inner to endodermis made up of Pericycle, VascuLar bundle & Pith.
Perlccle: A few layer of sclerenchyma outside the phloem, known as Hundk cap or Hard bast and also parenchynia cells between them constitute pericycic.
Vascular bundles:
Muscular bundles wedge-shaped arranged the form of a ring – (Eustelic)
Vascular bridle is made upon xylem. Phloem and cambium.
V – B is Conjoint, Collateral. Open and Endarch
Phloem: lies towards periphery.
Function: Conduction of organic food material
Cambium: brick-shaped thin-walled meristem responsible for secondary growth so. V – B is known as open V – B.
Function: Conduction of water and mineraLs from root to other parts.
Pith (Medulla): Central pith is present. It is parenchymatous.
Medullar ray: Pith extends between V – Bs as primary medullary ray.
FunctIon: Storage.

* A single layer of thin-walled cells with outer walls covered by thick cuticle.
* Stomata occur on both epidermis – stomata surrounded by dumbbell-shaped guard cells.
* Subsidiary cells: Surround guard cells.
* Bulliform cells: Occur on upper epidermis help for the rolling and un rolling of the leaf according to the weather change.
* Silica ceils: Some epidermal cells are filled with silica
Mesophyll:
* Grass, being isobilateral, mesophyll is not differentiated into palisade and spongy tissue, but compactly arranged cells with limited intercellular space.
Vascular Bundles:
* V.Bs differ in size – most of them are smaller, Large bundles occur at regular intervals
* Above and below large bundles sclerenchymatous patches occur – provide mechanical support, they are
* absent in small bundles.
* Bundle sheath – Each V.B is surrounded by a parenchymatous bundle sheath, generally contain starch grains.
* V.B has xylem upward and phloem towards the lower epidermis.
* V.Bs are Conjoint Collateral and Closed.
* In C 4 grasses the bundle sheath cells are called Kranz sheath, involve in C 4 cycle.

• Multiseriate upper and lower Epidermis.
• Thick cuticle on the surface of upper epidermis
• Mesophyll is distinguished in to upper palisade and lower spongy parenchyma.
• Well developed vascular bundles with upper xylem and lower phloem (conjoint collateral closed V.B).
• Sunken stomata on the lower epidermis with trichomes, to reduce the rate of transpiration.

Stomata
Hydathodes
1. Occur in the epidermis of leaves, young stems
Occur at the tip or margin of leaves that are grown in moist shady place.
2. Stomatal aperture is guarded by two guard cells
The aperture of hydathodes are surrounded by a ring of cuticularized cells
3. The two guard cells are generally surrounded by subsidiary cell.
Subsidiary cells are absent
4. Opening and closing of the stomatal aperture is regulated by guard cells.
Hydathodes pores remain always open.
4. These are involved in transpiration and exchange of gases.
These are involved in guttation