Ecosystem-Definition, Different types and Examples


  • The term ecosystem was coined by A.G. Tansley (1935)
  • It is a “Life supporting system”
  • Eco=region of space where organisms live
  • System =formed by interacting organism

Pond ecosystem

Definition: Ecosystem refers to the interactions of organisms with one another and with their environment in which they occur.
It is a “Life supporting system"
Ecosystem may be of two types: Natural and Artificial (Manmade)
Examples of ecosystem


The above figure gives you a summary of different types of ecosystems and examples of each type.
Each ecosystem may be considered as two layers, six structural components and six processes.
i)  Layers: Autotrophic layer and heterotrophic layer
Autotrophic layer or green belt within which the buildup of complex substances predominates using solar energy.
Heterotrophic layer or brown layer within which further manipulation and decomposition of the complex substances predominates.

ii)Structural components:
  • Inorganic substances: it involved n material cycles.
  • organic compounds that link biotic and Abiotic sectors.
  • Climatic regime :example rain fall, temperature
  • Producers mainly green plants that manufacture food from sunlight (light energy)
  • Consumers animals that consume other organisms and particulate organic matter-primary and secondary consumers.
  • Decomposers chiefly microbes that breakdown  complex compounds with release of products that are recycled by plants
iii)  Processes:
  • Energy flow
  • Food chains
  • Water and mineral nutrient cycles
  • Development and evolution (Succession)
  • Control (Cybernetics)

  • The term ecosystem was coined by A.G. Tansley (1935)
  • It is a “Life supporting system”
  • Eco=region of space where organisms live
  • System =formed by interacting organism

Pond ecosystem

Definition: Ecosystem refers to the interactions of organisms with one another and with their environment in which they occur.
It is a “Life supporting system"
Ecosystem may be of two types: Natural and Artificial (Manmade)
Examples of ecosystem


The above figure gives you a summary of different types of ecosystems and examples of each type.
Each ecosystem may be considered as two layers, six structural components and six processes.
i)  Layers: Autotrophic layer and heterotrophic layer
Autotrophic layer or green belt within which the buildup of complex substances predominates using solar energy.
Heterotrophic layer or brown layer within which further manipulation and decomposition of the complex substances predominates.

ii)Structural components:
  • Inorganic substances: it involved n material cycles.
  • organic compounds that link biotic and Abiotic sectors.
  • Climatic regime :example rain fall, temperature
  • Producers mainly green plants that manufacture food from sunlight (light energy)
  • Consumers animals that consume other organisms and particulate organic matter-primary and secondary consumers.
  • Decomposers chiefly microbes that breakdown  complex compounds with release of products that are recycled by plants
iii)  Processes:
  • Energy flow
  • Food chains
  • Water and mineral nutrient cycles
  • Development and evolution (Succession)
  • Control (Cybernetics)
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Notes on Equisetum Systematic Position, Morphology, Gametophyte and Life Cycle


Systematic Position
Division: Sphenophyta
Class: Calamopsida
Family: Equisitaceae
Genus: Equisetum (Horse tails, Scouring rushes) Only living member


Species: Common species include E. arvense (road side), E. debile (river side)Habitat: grows in swampy soil along river side or sandy road sides
Habit: Bushy, perennial herbs
Equisetum: Plant body
Equisetum Plant body

  •     Sporophytic plant body
  •       Differentiated into root, stem and leaves
  •      Creeping or erect plant body
  •      Stem: consist of underground rhizome and upright green aerial branches.
  •       Jointed stem with nodes and internodes, internodes with longitudinal ridges and furrows and hollow interior
  •      Silica deposits in stem make it rough (Scouring rushes)
  •        Leaves: nodes with small, sessile microphyllous scale leaves in whorls
  •        Function: photosynthesis
  •      Fertile branches bear strobili after some vegetative growth
  •        Roots: Adventitious roots arise from the nodes of rhizome
  •      Other features: Homosporous nature, Eusporangiate
Equisetum Stem Anatomy T.S
     Vegetative Reproduction:  Fragmentation of rhizome, Tubers formed on rhizome
Strobilus or structure of cone
STROBILUS OF EQUISETUM

  •  Equisetum is homosporous and Eusporangiate
  •   Strobili are borne terminally and singly on aerial fertile branches.
  • Strobilus consists of a central axis on which stalked sporangiophores with sporangium are arranged in whorls
     Sporangiophore
·         Umbrella shaped structure with a slender stalk and a hexagonal peltate disc
·         The underside of peltate disc bears variable number of sac like sporangia
·         The number of sporangia in each sporangiophore may vary from 5-10
·         Sporangium consists of a 2 cell thick wall, with large number of homosporous spores.  Dehiscence along longitudinal slit. Spores are dispersed by  wind with the help of elaters
Spores and Elators
          Spores are Green, large, uninucleate, spherical, chloroplast containing structures with exine, intine and outermost epispore
          Elaters are spirally coiled , spoon shaped hygroscopic structures formed from epispore of haploid spore
          Each spore has 4 spirally arranged hygroscopic elaters
          Function: helps in dehiscence of sporangium and spore dispersal
Gametophyte or prothallus of Equisetum
Gametophyte or prothallus of Equisetum

  •     Spores falling on suitable substratum germinate to form green prothallus with rhizoids for fixation.
  •      Prothallus consists of a basal disc and number of green vertical lobes.
  •       Monoecious or bisexual: both antheridia and archegonia are present.
  •      Antheridia may occur on vertical lobes or basal disc embedded.
  •       Antheridium produces 256-512multiflagellate, spirally coiled spermatozoids.
  •      Archegonia flask shaped structures at the base of vertical lobes.
  •       Fusion forms embryo which give rise to new plant.
     Life cycle: Homomorphic alternation of generation
Life cycle of Equisetum

Systematic Position
Division: Sphenophyta
Class: Calamopsida
Family: Equisitaceae
Genus: Equisetum (Horse tails, Scouring rushes) Only living member


Species: Common species include E. arvense (road side), E. debile (river side)Habitat: grows in swampy soil along river side or sandy road sides
Habit: Bushy, perennial herbs
Equisetum: Plant body
Equisetum Plant body

  •     Sporophytic plant body
  •       Differentiated into root, stem and leaves
  •      Creeping or erect plant body
  •      Stem: consist of underground rhizome and upright green aerial branches.
  •       Jointed stem with nodes and internodes, internodes with longitudinal ridges and furrows and hollow interior
  •      Silica deposits in stem make it rough (Scouring rushes)
  •        Leaves: nodes with small, sessile microphyllous scale leaves in whorls
  •        Function: photosynthesis
  •      Fertile branches bear strobili after some vegetative growth
  •        Roots: Adventitious roots arise from the nodes of rhizome
  •      Other features: Homosporous nature, Eusporangiate
Equisetum Stem Anatomy T.S
     Vegetative Reproduction:  Fragmentation of rhizome, Tubers formed on rhizome
Strobilus or structure of cone
STROBILUS OF EQUISETUM

  •  Equisetum is homosporous and Eusporangiate
  •   Strobili are borne terminally and singly on aerial fertile branches.
  • Strobilus consists of a central axis on which stalked sporangiophores with sporangium are arranged in whorls
     Sporangiophore
·         Umbrella shaped structure with a slender stalk and a hexagonal peltate disc
·         The underside of peltate disc bears variable number of sac like sporangia
·         The number of sporangia in each sporangiophore may vary from 5-10
·         Sporangium consists of a 2 cell thick wall, with large number of homosporous spores.  Dehiscence along longitudinal slit. Spores are dispersed by  wind with the help of elaters
Spores and Elators
          Spores are Green, large, uninucleate, spherical, chloroplast containing structures with exine, intine and outermost epispore
          Elaters are spirally coiled , spoon shaped hygroscopic structures formed from epispore of haploid spore
          Each spore has 4 spirally arranged hygroscopic elaters
          Function: helps in dehiscence of sporangium and spore dispersal
Gametophyte or prothallus of Equisetum
Gametophyte or prothallus of Equisetum

  •     Spores falling on suitable substratum germinate to form green prothallus with rhizoids for fixation.
  •      Prothallus consists of a basal disc and number of green vertical lobes.
  •       Monoecious or bisexual: both antheridia and archegonia are present.
  •      Antheridia may occur on vertical lobes or basal disc embedded.
  •       Antheridium produces 256-512multiflagellate, spirally coiled spermatozoids.
  •      Archegonia flask shaped structures at the base of vertical lobes.
  •       Fusion forms embryo which give rise to new plant.
     Life cycle: Homomorphic alternation of generation
Life cycle of Equisetum
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Equisetum Stem Anatomy T.S

Equisetum morphology
Equisetum Stem Anatomy

·         Epidermis is single layered with stomata and heavily coated with silica deposits
·         Outer cortex is sclerenchymatous and chlorenchymatous
·         Often sclerenchaymatous below ridges followed by chlorenchymatous region
·         Inner cortex is made up of large parenchymatous cells with vallecular canals.
·         Vallecular canals are large air filled, intercellular spaces below the furrows in inner cortex
·         It is a hydrophytic character
·         Endodermis and pericycle single layered
·         Stele: Eustele, siphonostele; ring of vascular bundles below the ridges.
·         Vascular bundle is conjoint, collateral and closed and separated from one another by parenchyma
·         V.B consists of xylem, phloem and carinal canal
·         Xylem is poorly developed.
·         Carinal canal is a water filled region present in the vascular bundle.
·         Formed by the disintegration of protoxylem tracheids

·         Pith: Large central cavity filled with water (hydrophytic character)
Equisetum morphology
Equisetum Stem Anatomy

·         Epidermis is single layered with stomata and heavily coated with silica deposits
·         Outer cortex is sclerenchymatous and chlorenchymatous
·         Often sclerenchaymatous below ridges followed by chlorenchymatous region
·         Inner cortex is made up of large parenchymatous cells with vallecular canals.
·         Vallecular canals are large air filled, intercellular spaces below the furrows in inner cortex
·         It is a hydrophytic character
·         Endodermis and pericycle single layered
·         Stele: Eustele, siphonostele; ring of vascular bundles below the ridges.
·         Vascular bundle is conjoint, collateral and closed and separated from one another by parenchyma
·         V.B consists of xylem, phloem and carinal canal
·         Xylem is poorly developed.
·         Carinal canal is a water filled region present in the vascular bundle.
·         Formed by the disintegration of protoxylem tracheids

·         Pith: Large central cavity filled with water (hydrophytic character)
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Complex Tissues in Plants - Xylem and Phloem

A tissue made up of more than one type of cells functioning as a unit is called complex tissue. The vascular tissues as known as complex tissues. Xylem and Phloem are together called conducting tissues (vascular tissues) and are organised into vascular bundles. 
Types of Complex Tissues: Xylem and Phloem
Complex tissues in plants
Refer: Difference between Xylem and Phloem
A tissue made up of more than one type of cells functioning as a unit is called complex tissue. The vascular tissues as known as complex tissues. Xylem and Phloem are together called conducting tissues (vascular tissues) and are organised into vascular bundles. 
Types of Complex Tissues: Xylem and Phloem
Complex tissues in plants
Refer: Difference between Xylem and Phloem
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Different Types of Sclerenchyma -Fiberes and Sclereids and their Function

Sclerenchyma: (Gk; Sclerous: hard; enchyma: infusion)
       Non-living mechanical tissue
       Thick walled, lignified and pitted cells without protoplasm at maturity
       Distribution: cortex, hypodermis, vascular regions of stem, leaves, fruit wall etc
Types of Sclerenchyma - Fibres and Sclereids
    1. Sclerenchyma Fibres

Sclerenchyma Fibres

  • Thick, elongated, spindle shaped cells with pointed tips.
  • Narrow lumen with simple rounded pits and lignified secondary wall
  • Distribution: cortex, pericycle, xylem and phloem
Types of Fibres:
  • a. Surface fibres: found on fruit wall and seed coat (e.g., coconut)
  • b. Xylary or Wood fibres: associated with xylem
  • c. Extraxylary or Bast fibres: seen associated with cortex, pericycle and phloem
Function of Fibres:
  • Provide mechanical support to the plant parts
  • Surface fibres help in seed and fruit dispersal
      2. Sclereids
Sclereids
       Small sclerenchymatous cells with highly thickened lignified walls and narrow lumen. 
      Distribution: pulp of fruits, fruit walls, cortex, pith etc





  Different types of Sclereids
Different types of Sclereids

       a. Brachysclereids: isodiametric sclerieds called as stone cells
Grit cells: Numerous Stone cells present in the pulp of fruits (guava, sapota)
Distribution: cortex, pith, pericarp of coconut shell
       b. Macrosclereids: rod like sclerieds- present in bark and seed coat of leguminous plants
       c. Osteosclerieds: Bone like sclerieds with lobed ends-seed coat and fruit wall
       d. Astrosclereids: star shaped sclerieds- dicot leaves and gymnosperms

Functions of Scelrenchyma
  • Dead mechanical tissue providing strength and support to the plant
  • Protects from damages
  • Xylem fibres in water conduction
  •  Fibrous sclerenchyma of fruits and seeds helps in seed dispersal.
Sclerenchyma: (Gk; Sclerous: hard; enchyma: infusion)
       Non-living mechanical tissue
       Thick walled, lignified and pitted cells without protoplasm at maturity
       Distribution: cortex, hypodermis, vascular regions of stem, leaves, fruit wall etc
Types of Sclerenchyma - Fibres and Sclereids
    1. Sclerenchyma Fibres

Sclerenchyma Fibres

  • Thick, elongated, spindle shaped cells with pointed tips.
  • Narrow lumen with simple rounded pits and lignified secondary wall
  • Distribution: cortex, pericycle, xylem and phloem
Types of Fibres:
  • a. Surface fibres: found on fruit wall and seed coat (e.g., coconut)
  • b. Xylary or Wood fibres: associated with xylem
  • c. Extraxylary or Bast fibres: seen associated with cortex, pericycle and phloem
Function of Fibres:
  • Provide mechanical support to the plant parts
  • Surface fibres help in seed and fruit dispersal
      2. Sclereids
Sclereids
       Small sclerenchymatous cells with highly thickened lignified walls and narrow lumen. 
      Distribution: pulp of fruits, fruit walls, cortex, pith etc





  Different types of Sclereids
Different types of Sclereids

       a. Brachysclereids: isodiametric sclerieds called as stone cells
Grit cells: Numerous Stone cells present in the pulp of fruits (guava, sapota)
Distribution: cortex, pith, pericarp of coconut shell
       b. Macrosclereids: rod like sclerieds- present in bark and seed coat of leguminous plants
       c. Osteosclerieds: Bone like sclerieds with lobed ends-seed coat and fruit wall
       d. Astrosclereids: star shaped sclerieds- dicot leaves and gymnosperms

Functions of Scelrenchyma
  • Dead mechanical tissue providing strength and support to the plant
  • Protects from damages
  • Xylem fibres in water conduction
  •  Fibrous sclerenchyma of fruits and seeds helps in seed dispersal.
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Collenchyma Structure and Function

       Living mechanical tissue with thickened corners
       A typical supporting tissue of growing organs and mature herbaceous organs that      lack secondary growth or only slightly modified by secondary growth
       Function: provide tensile strength to organs
       Distribution: In dicots, hypodermis of stem, petiole, petals of flowers etc
       Sometimes act as meristamatic cells (cork cambium)

Collenchyma with thickened corners

Function of Collenchyma:
       Living mechanical tissue specifically adapted for supporting growing organs
       Prevents bending and breaking of stems by wind due to its tensile strength
       Some possess chloroplast and carry out photosynthesis
       Gives flexibility to plant organs during their growth

Refer: Difference between Parenchyma and Collenchyma
       Living mechanical tissue with thickened corners
       A typical supporting tissue of growing organs and mature herbaceous organs that      lack secondary growth or only slightly modified by secondary growth
       Function: provide tensile strength to organs
       Distribution: In dicots, hypodermis of stem, petiole, petals of flowers etc
       Sometimes act as meristamatic cells (cork cambium)

Collenchyma with thickened corners

Function of Collenchyma:
       Living mechanical tissue specifically adapted for supporting growing organs
       Prevents bending and breaking of stems by wind due to its tensile strength
       Some possess chloroplast and carry out photosynthesis
       Gives flexibility to plant organs during their growth

Refer: Difference between Parenchyma and Collenchyma
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Parenchyma: Different types, Structure and Function

Parenchyma
•Simplest and the least specialized living tissue.
•Fundamental tissue of the plant body
•Shape: isodiametric or polygonal
•Thin walled with prominent nucleus and vacoulated cytoplasm.
•Distribution: all parts of the plant body.
•Epidermis, cortex, pith, leaf mesophyll, fruit, endosperm.
Different types of Parenchyma
Different types of Parenchyma based on structure and function

Different types of parenchyma diagram
Functions of Parenchyma:
•Fundamental tissue of the plant body
•Storage of reserve food materials
•Bouyancy and gaseous exchange in hydrophytes by aerenchyma
•Mechanical support especially prosenchyma
•Xylem and phloem parenchyma helps in transport of materials
•Parenchyma regains dividing capacity and forms secondary meristems
Parenchyma
•Simplest and the least specialized living tissue.
•Fundamental tissue of the plant body
•Shape: isodiametric or polygonal
•Thin walled with prominent nucleus and vacoulated cytoplasm.
•Distribution: all parts of the plant body.
•Epidermis, cortex, pith, leaf mesophyll, fruit, endosperm.
Different types of Parenchyma
Different types of Parenchyma based on structure and function

Different types of parenchyma diagram
Functions of Parenchyma:
•Fundamental tissue of the plant body
•Storage of reserve food materials
•Bouyancy and gaseous exchange in hydrophytes by aerenchyma
•Mechanical support especially prosenchyma
•Xylem and phloem parenchyma helps in transport of materials
•Parenchyma regains dividing capacity and forms secondary meristems
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Difference between Fibres and Sclereids

The cells of sclerenchyma vary in size and shape. They are placed in two groups: the fibres and sclereids. The cells of the fibres are elongate whereas the cells of sclereids are short isodiametric or irregular in shape.
                                           Fibres vs Sclereids
Fibres
  1. Fibres are elongated
  2. Have tapering end walls
  3. Generally unbranched.
  4. Originate from meristematic cells.
Sclereids (Sclerotic cells)

  1. Sclerids are broad.
  2. End walls are blunt
  3. May be branched or unbranched.
  4. They are formed secondarily by the thickening of parenchyma cells 
The cells of sclerenchyma vary in size and shape. They are placed in two groups: the fibres and sclereids. The cells of the fibres are elongate whereas the cells of sclereids are short isodiametric or irregular in shape.
                                           Fibres vs Sclereids
Fibres
  1. Fibres are elongated
  2. Have tapering end walls
  3. Generally unbranched.
  4. Originate from meristematic cells.
Sclereids (Sclerotic cells)

  1. Sclerids are broad.
  2. End walls are blunt
  3. May be branched or unbranched.
  4. They are formed secondarily by the thickening of parenchyma cells 
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Difference between Corm and Rhizome

Rhizome and corm are the underground stem modifications in which stems are seen below the surface of the soil and are modified to store the food.
Rhizome vs Corm
Rhizome

1.       It is flattened underground stem.
2.       It grows horizontantly
3.       Adventitious roots arise profusely from nodes

Example of Rhizome: Ginger, Canna, Turmeric, Banana
Corm

1.       It is cylindrical underground stem
2.       It grows vertically
3.       Adventitious roots arise from the lower nodes of the corm

Example of Corm: Gladious, Colocasia Amorphophallus
Rhizome and corm are the underground stem modifications in which stems are seen below the surface of the soil and are modified to store the food.
Rhizome vs Corm
Rhizome

1.       It is flattened underground stem.
2.       It grows horizontantly
3.       Adventitious roots arise profusely from nodes

Example of Rhizome: Ginger, Canna, Turmeric, Banana
Corm

1.       It is cylindrical underground stem
2.       It grows vertically
3.       Adventitious roots arise from the lower nodes of the corm

Example of Corm: Gladious, Colocasia Amorphophallus
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What are Knots?

Definition:
knots
Knots
The portion of the branches enclosed within the woods are called knots.
It is a type of natural defect in timber
Knots disfigure the appearance and reduces the strength of wood.

Based on size, knots are classified into 4 types, pin knots, small knots, medium knots and large knots.
Definition:
knots
Knots
The portion of the branches enclosed within the woods are called knots.
It is a type of natural defect in timber
Knots disfigure the appearance and reduces the strength of wood.

Based on size, knots are classified into 4 types, pin knots, small knots, medium knots and large knots.
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Anomalous Secondary Thickening in Dracaena, a Monocot

Dracaena is a typical example of Anomalous secondary thickening  in monocots.
Typically, secondary thickening is absent in monocots. Therefore, secondary thickening itself is an anomaly as Dracaena is a monocot.
Dracaena young stem cross section
Young stem has typical monocot structure
1.Epidermis single layered
2.Hypodermis is sclerenchymatous
3.Numerous closed, collateral vascular bundles scattered in the parenchymatous ground tissue
4.Xylem is endarch
Anomalous secondary thickening in Dracaena
In Dracaena, secondary growth is due to
a) Extrastelar cambial ring in a monocot stem at the cortex
b) Abnormal activity of cambium
Dracaena anomalous secondary thickening TS, cross section
During Secondary thickening
1.Formation of secondary meristem or secondary cambium occurs in the inner region of parenchymatous cortex
2.The activity of cambium is abnormal
3.It produces secondary vascular bundles on its inner side only and parenchymatous cells on the outer side.
4.The secondary vascular bundles are amphivasal where phloem is surrounded by xylem
5.Later cambium produces more parenchymatous cells to the inside that pushes newly formed vascular bundles to the centre. The activity and position of vascular bundles keep on changing and vascular bundles are arranged in concentric rings. The second ring of vascular bundles is alternating in position with the first ring. The vascular bundles in the last inner ring are embedded in a mass of lignified conjunctive tissue.
6.Cork cambium activity is normal and produces cork and secondary cortex at the outer region.
See notes on Anomalous Secondary Thickening in Bignonia
Dracaena is a typical example of Anomalous secondary thickening  in monocots.
Typically, secondary thickening is absent in monocots. Therefore, secondary thickening itself is an anomaly as Dracaena is a monocot.
Dracaena young stem cross section
Young stem has typical monocot structure
1.Epidermis single layered
2.Hypodermis is sclerenchymatous
3.Numerous closed, collateral vascular bundles scattered in the parenchymatous ground tissue
4.Xylem is endarch
Anomalous secondary thickening in Dracaena
In Dracaena, secondary growth is due to
a) Extrastelar cambial ring in a monocot stem at the cortex
b) Abnormal activity of cambium
Dracaena anomalous secondary thickening TS, cross section
During Secondary thickening
1.Formation of secondary meristem or secondary cambium occurs in the inner region of parenchymatous cortex
2.The activity of cambium is abnormal
3.It produces secondary vascular bundles on its inner side only and parenchymatous cells on the outer side.
4.The secondary vascular bundles are amphivasal where phloem is surrounded by xylem
5.Later cambium produces more parenchymatous cells to the inside that pushes newly formed vascular bundles to the centre. The activity and position of vascular bundles keep on changing and vascular bundles are arranged in concentric rings. The second ring of vascular bundles is alternating in position with the first ring. The vascular bundles in the last inner ring are embedded in a mass of lignified conjunctive tissue.
6.Cork cambium activity is normal and produces cork and secondary cortex at the outer region.
See notes on Anomalous Secondary Thickening in Bignonia
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Anomalous Secondary Thickening in Bignonia

Bignonia belongs to the family Bignoniaceae.
Bignonia young stem cross section details:
1.Wavy outline with prominent ridges and furrows
2.Epidermis single layered with cuticle
3.Hypodermis is collenchymatous
4.Cortex is parenchymatous
5.Endodermis not prominent
6.Pericycle unilayered
7.Vascular Bundles are conjoint, collateral, open and arranged in a ring around pith
8.Xylem is endarch
Bignonia: Anomalous secondary thickening
Anomalous Secondary Thickening in Bignonia cross section c.s
Anomalous secondary thickening is due to the
a) Abnormal functioning of cambium.
During Secondary thickening
1.At the beginning, fascicular cambium and interfascicular cambium join to form a cambial ring. The cambium behaves normally producing more secondary xylem towards the inner side and less secondary phloem to the outside.
2.After some time, the cambium develops unidirectional areas of abnormal activity at four diagonal points. At this points, cambium produces lesser amount of secondary xylem and more amount of secondary phloem
3.This phloem masses form four deep wedges supported by transverse bands of sclerotic cells
4.Thus four wedges of secondary phloem intrudes into secondary xylem.
5.Thus 4 wedges of secondary phloem and 4 ridges of secondary xylem are formed.
6.Periderm formation is normal as activity of cork cambium is normal
See notes on Anomalous Secondary thickening in Dracaena
Bignonia belongs to the family Bignoniaceae.
Bignonia young stem cross section details:
1.Wavy outline with prominent ridges and furrows
2.Epidermis single layered with cuticle
3.Hypodermis is collenchymatous
4.Cortex is parenchymatous
5.Endodermis not prominent
6.Pericycle unilayered
7.Vascular Bundles are conjoint, collateral, open and arranged in a ring around pith
8.Xylem is endarch
Bignonia: Anomalous secondary thickening
Anomalous Secondary Thickening in Bignonia cross section c.s
Anomalous secondary thickening is due to the
a) Abnormal functioning of cambium.
During Secondary thickening
1.At the beginning, fascicular cambium and interfascicular cambium join to form a cambial ring. The cambium behaves normally producing more secondary xylem towards the inner side and less secondary phloem to the outside.
2.After some time, the cambium develops unidirectional areas of abnormal activity at four diagonal points. At this points, cambium produces lesser amount of secondary xylem and more amount of secondary phloem
3.This phloem masses form four deep wedges supported by transverse bands of sclerotic cells
4.Thus four wedges of secondary phloem intrudes into secondary xylem.
5.Thus 4 wedges of secondary phloem and 4 ridges of secondary xylem are formed.
6.Periderm formation is normal as activity of cork cambium is normal
See notes on Anomalous Secondary thickening in Dracaena
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What is Bark?

Bark is the thick extrastelar outer covering.
It consists of periderm and secondary phloem. So it consists of all living and dead cells outside vascular cambium. (primary and secondary phloem, phelloderm, phellogen and phellum).
bark
The cork part of the bark in commercially important.
-Used in making of bottle cork, shock absorbers, sports goods etc.
Bark is formed associated with secondary thickening
Bark is the thick extrastelar outer covering.
It consists of periderm and secondary phloem. So it consists of all living and dead cells outside vascular cambium. (primary and secondary phloem, phelloderm, phellogen and phellum).
bark
The cork part of the bark in commercially important.
-Used in making of bottle cork, shock absorbers, sports goods etc.
Bark is formed associated with secondary thickening
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Difference between Manoxylic wood and Pycnoxylic wood

Wood of Gymnosperms are classified into manoxylic or pycnoylic. This classification is based on the amount of xylem cells in the wood.
manoxylic and pycnoxylic wood
Manoxylic wood:
It is the non-compact wood with large amount of parenchyma, large pith and cortex mixed with less amount of xylem tracheids or wood.
-Parenchyma cells are filled with starch grains
-Not important commercially as wood is not durable
-In Cycas

Pycnoxylic wood:
It is the compact strong wood with large amount of xylem tracheids or wood and small amount of cortex and pith with little Parenchyma.
-Durable and yields timber
-In Pinus
Wood of Gymnosperms are classified into manoxylic or pycnoylic. This classification is based on the amount of xylem cells in the wood.
manoxylic and pycnoxylic wood
Manoxylic wood:
It is the non-compact wood with large amount of parenchyma, large pith and cortex mixed with less amount of xylem tracheids or wood.
-Parenchyma cells are filled with starch grains
-Not important commercially as wood is not durable
-In Cycas

Pycnoxylic wood:
It is the compact strong wood with large amount of xylem tracheids or wood and small amount of cortex and pith with little Parenchyma.
-Durable and yields timber
-In Pinus
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Definition and Characteristics of Meristems

We have a definite growth pattern and growth stops at certain stage or age. But plant growth is indefinite. All the time, the plant body possess certain cells that are actively dividing and adding new cells thereby effecting growth. These cells are called as meristem.
Definition: Meristems are actively dividing immature cells that form new cells by cell division.
Shoot and root meristem
Characteristics of Meristamatic cells
1. Isodiametric, spherical, oval or polygonal cells
2. Thin walled as these cells are in continuous division
3. Large nucleus
4. Dense protoplasm
5. Less number of vacuoles
6. Arranged without intercellular spaces
7. Always in active metabolic state
The above characters are typical of cells with high metabolic activity.
Learn more:
Plant Meristem: Definition and Classification based on origin, position and plane of division
We have a definite growth pattern and growth stops at certain stage or age. But plant growth is indefinite. All the time, the plant body possess certain cells that are actively dividing and adding new cells thereby effecting growth. These cells are called as meristem.
Definition: Meristems are actively dividing immature cells that form new cells by cell division.
Shoot and root meristem
Characteristics of Meristamatic cells
1. Isodiametric, spherical, oval or polygonal cells
2. Thin walled as these cells are in continuous division
3. Large nucleus
4. Dense protoplasm
5. Less number of vacuoles
6. Arranged without intercellular spaces
7. Always in active metabolic state
The above characters are typical of cells with high metabolic activity.
Learn more:
Plant Meristem: Definition and Classification based on origin, position and plane of division
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