- Anatomy is the study of internal structure of plants and other organisms.
THE TISSUES
- A tissue is a group of cells having common origin and - Cells are generally isodiametric. They may be spherical,
function. oval, round, polygonal or elongated.
- Based on the capability of cell division, plant tissues are 2 - Their walls are thin and made up
groups: Meristematic and Permanent. of cellulose.
- Cells are closely packed or have
MERISTEMATIC TISSUES (MERISTEMS)
small intercellular spaces.
These are the tissues where active cell division and growth
- Functions: Photosynthesis,
occurs. Based on the position, meristems are 3 types:
storage, secretion etc.
o Apical meristems: They occur at the tips of roots and
shoots and produce primary tissues. It is 2 types: b. Collenchyma
§ Root apical meristem: It occupies the tip of a root. - It occurs in layers below the
§ Shoot apical meristem: It occupies the distant most epidermis in dicot plants.
region of the stem axis. Some cells ‘left behind’ from - It is found as a homogeneous
shoot apical meristem, constitute the axillary bud. They layer or in patches.
are present in the axils of leaves and can form a branch - It consists of cells with much
or a flower. thickened corners due to
deposition of cellulose, hemicellulose and pectin.
- Intercellular spaces are absent.
- Cells are oval, spherical or polygonal and often contain
chloroplasts.
- Functions: They provide mechanical support to the
growing parts such as young stem and petiole of a leaf. The
cells that contain chloroplasts assimilate food.
c. Sclerenchyma
- It consists of long,
o Intercalary meristems: They occur between mature narrow cells with thick
tissues. They occur in grasses and regenerate parts and lignified cell walls
removed by the grazing herbivores. having a few or
Apical and intercalary meristems are primary meristems numerous pits.
because they appear early in a plant life and contribute to - They are usually dead
the formation of primary plant body. During that, specific without protoplasts.
regions of the apical meristem produce dermal tissues, - Based on the form, structure, origin and development,
ground tissues and vascular tissues. sclerenchyma is 2 types: fibres & sclereids.
o Secondary (lateral) meristems: The meristems that occur o Fibres: These are thick-walled, elongated and pointed
in mature regions of roots and shoots. They are cylindrical cells, generally occurring in groups.
meristems. They are seen in gymnosperms and dicots. o Sclereids: These are spherical, oval or cylindrical,
E.g. Fascicular vascular cambium, interfascicular highly thickened dead cells with very narrow cavities
cambium & cork cambium. These are responsible for (lumen). These are found in the fruit walls of nuts; pulp
producing the secondary tissues. of fruits like guava, pear and sapota; seed coats of
PERMANENT (MATURE) TISSUES legumes and leaves of tea.
- The cells produced by primary and secondary meristems, - Function: It provides mechanical support to organs.
become structurally and functionally specialized and lose 2. Complex Permanent Tissues
the ability to divide. They are called permanent (mature) - These are made of more than one type of cells and they
cells and constitute the permanent tissues. work together as a unit.
- They are 2 types: Simple and Complex. - 2 types: Xylem and Phloem.
1. Simple Permanent Tissues a. Xylem
- The tissues having all cells similar in structure & function. - It functions as a conducting tissue for water and minerals
- 3 types: Parenchyma, Collenchyma and Sclerenchyma. from roots to the stem and leaves.
a. Parenchyma - It also provides mechanical strength to the plant parts.
- It forms the major component within organs. - It is composed of 4 kinds of elements: tracheids, vessels,
xylem fibres and xylem parenchyma.
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, o Tracheids: These are elongated tube like o Sieve tube elements: These are long, tube-like structures,
dead cells with thick and lignified walls arranged longitudinally and are associated with companion
and tapering ends. Protoplasm absent. cells. Their end walls are
The inner layers of cell walls have perforated to form the sieve
thickenings which vary in form. In plates. A mature sieve element
flowering plants, tracheids & vessels are has a peripheral cytoplasm and a
the main water transporting elements. large vacuole but lacks a nucleus.
o Vessel: It is a long cylindrical tube-like The functions of sieve tubes are
structure made up of many cells (vessel controlled by the nucleus of
members), each with lignified walls and companion cells.
a large central cavity. Protoplasm absent. The first formed primary phloem (protophloem) consists
Vessel members are interconnected through perforations in of narrow sieve tubes. The later formed phloem
their common walls. The vessels are a characteristic (metaphloem) has bigger sieve tubes.
feature of angiosperms. Gymnosperms lack vessels. Function: Conduction of food materials from leaves.
o Xylem fibres: They have highly thickened walls and o Companion cells: Specialized parenchymatous cells
obliterated central lumens. They are septate or aseptate. closely associated with sieve tube elements. Sieve tube
o Xylem parenchyma: Living and thin-walled cells with elements & companion cells are connected by pit fields
cellulosic cell walls. They store food materials (starch or present between their common longitudinal walls.
fat) and other substances like tannins. Radial conduction of Function: Maintain the pressure gradient in sieve tubes.
water takes place by the ray parenchymatous cells. o Phloem parenchyma: It is made up of elongated, tapering
- Primary xylem is 2 types: cylindrical cells which have dense cytoplasm and nucleus.
o Protoxylem: The first formed primary xylem. The cell wall is composed of cellulose and has pits through
o Metaxylem: The later formed primary xylem. which plasmodesmatal connections exist between the cells.
- In stems, the protoxylem lies towards the centre (pith) and Phloem parenchyma is absent in most of the monocots.
the metaxylem lies towards the periphery of the organ. This Function: It stores food material and other substances like
type of primary xylem is called endarch. resins, latex and mucilage.
- In roots, the protoxylem lies towards periphery and o Phloem fibres (bast fibres): These are made up of
metaxylem lies towards the centre. Such arrangement of sclerenchymatous cells. Generally absent in primary
primary xylem is called exarch. phloem but are found in the secondary phloem. These are
b. Phloem (Bast) much elongated, unbranched and have pointed, needle like
It transports food materials from leaves to other parts. apices. Cell wall is quite thick. At maturity, these fibres
In angiosperms, phloem is composed of sieve tube elements, lose their protoplasm and become dead. Phloem fibres of
companion cells, phloem parenchyma & phloem fibres. jute, flax and hemp are used commercially.
Gymnosperms have albuminous cells and sieve cells. They Function: Mechanical support & protection to soft tissues.
lack sieve tubes and companion cells.
THE TISSUE SYSTEM
Based on structure and location, tissue systems are 3 types: Stomata
o Epidermal tissue system - These are structures present in the epidermis of leaves.
o Ground (fundamental) tissue system - Stomata regulate the transpiration and gaseous exchange.
o Vascular (conducting) tissue system - A stoma is made of two bean-shaped cells (guard cells).
1. Epidermal Tissue System - In grasses, the guard cells are dumbbell shaped.
- It forms the outer-most covering of the whole plant body.
- It comprises epidermal cells, stomata and epidermal
appendages (trichomes & hairs).
Epidermis
- It is the outermost layer of the primary plant body.
- Epidermis is usually single layered. - The outer walls of guard cells (away from the stomatal
- It is made up of elongated, compactly arranged pore) are thin and the inner walls (towards the stomatal
parenchymatous cells with a small amount of cytoplasm pore) are highly thickened.
lining the cell wall and a large vacuole. - The guard cells possess chloroplasts and regulate the
- The outside of the epidermis is often covered with a waxy opening and closing of stomata.
thick layer (cuticle). It prevents the loss of water. Cuticle - Sometimes, a few epidermal cells near the guard cells
is absent in roots. become specialized in their shape and size. They are
known as subsidiary cells.
2
THE TISSUES
- A tissue is a group of cells having common origin and - Cells are generally isodiametric. They may be spherical,
function. oval, round, polygonal or elongated.
- Based on the capability of cell division, plant tissues are 2 - Their walls are thin and made up
groups: Meristematic and Permanent. of cellulose.
- Cells are closely packed or have
MERISTEMATIC TISSUES (MERISTEMS)
small intercellular spaces.
These are the tissues where active cell division and growth
- Functions: Photosynthesis,
occurs. Based on the position, meristems are 3 types:
storage, secretion etc.
o Apical meristems: They occur at the tips of roots and
shoots and produce primary tissues. It is 2 types: b. Collenchyma
§ Root apical meristem: It occupies the tip of a root. - It occurs in layers below the
§ Shoot apical meristem: It occupies the distant most epidermis in dicot plants.
region of the stem axis. Some cells ‘left behind’ from - It is found as a homogeneous
shoot apical meristem, constitute the axillary bud. They layer or in patches.
are present in the axils of leaves and can form a branch - It consists of cells with much
or a flower. thickened corners due to
deposition of cellulose, hemicellulose and pectin.
- Intercellular spaces are absent.
- Cells are oval, spherical or polygonal and often contain
chloroplasts.
- Functions: They provide mechanical support to the
growing parts such as young stem and petiole of a leaf. The
cells that contain chloroplasts assimilate food.
c. Sclerenchyma
- It consists of long,
o Intercalary meristems: They occur between mature narrow cells with thick
tissues. They occur in grasses and regenerate parts and lignified cell walls
removed by the grazing herbivores. having a few or
Apical and intercalary meristems are primary meristems numerous pits.
because they appear early in a plant life and contribute to - They are usually dead
the formation of primary plant body. During that, specific without protoplasts.
regions of the apical meristem produce dermal tissues, - Based on the form, structure, origin and development,
ground tissues and vascular tissues. sclerenchyma is 2 types: fibres & sclereids.
o Secondary (lateral) meristems: The meristems that occur o Fibres: These are thick-walled, elongated and pointed
in mature regions of roots and shoots. They are cylindrical cells, generally occurring in groups.
meristems. They are seen in gymnosperms and dicots. o Sclereids: These are spherical, oval or cylindrical,
E.g. Fascicular vascular cambium, interfascicular highly thickened dead cells with very narrow cavities
cambium & cork cambium. These are responsible for (lumen). These are found in the fruit walls of nuts; pulp
producing the secondary tissues. of fruits like guava, pear and sapota; seed coats of
PERMANENT (MATURE) TISSUES legumes and leaves of tea.
- The cells produced by primary and secondary meristems, - Function: It provides mechanical support to organs.
become structurally and functionally specialized and lose 2. Complex Permanent Tissues
the ability to divide. They are called permanent (mature) - These are made of more than one type of cells and they
cells and constitute the permanent tissues. work together as a unit.
- They are 2 types: Simple and Complex. - 2 types: Xylem and Phloem.
1. Simple Permanent Tissues a. Xylem
- The tissues having all cells similar in structure & function. - It functions as a conducting tissue for water and minerals
- 3 types: Parenchyma, Collenchyma and Sclerenchyma. from roots to the stem and leaves.
a. Parenchyma - It also provides mechanical strength to the plant parts.
- It forms the major component within organs. - It is composed of 4 kinds of elements: tracheids, vessels,
xylem fibres and xylem parenchyma.
1
, o Tracheids: These are elongated tube like o Sieve tube elements: These are long, tube-like structures,
dead cells with thick and lignified walls arranged longitudinally and are associated with companion
and tapering ends. Protoplasm absent. cells. Their end walls are
The inner layers of cell walls have perforated to form the sieve
thickenings which vary in form. In plates. A mature sieve element
flowering plants, tracheids & vessels are has a peripheral cytoplasm and a
the main water transporting elements. large vacuole but lacks a nucleus.
o Vessel: It is a long cylindrical tube-like The functions of sieve tubes are
structure made up of many cells (vessel controlled by the nucleus of
members), each with lignified walls and companion cells.
a large central cavity. Protoplasm absent. The first formed primary phloem (protophloem) consists
Vessel members are interconnected through perforations in of narrow sieve tubes. The later formed phloem
their common walls. The vessels are a characteristic (metaphloem) has bigger sieve tubes.
feature of angiosperms. Gymnosperms lack vessels. Function: Conduction of food materials from leaves.
o Xylem fibres: They have highly thickened walls and o Companion cells: Specialized parenchymatous cells
obliterated central lumens. They are septate or aseptate. closely associated with sieve tube elements. Sieve tube
o Xylem parenchyma: Living and thin-walled cells with elements & companion cells are connected by pit fields
cellulosic cell walls. They store food materials (starch or present between their common longitudinal walls.
fat) and other substances like tannins. Radial conduction of Function: Maintain the pressure gradient in sieve tubes.
water takes place by the ray parenchymatous cells. o Phloem parenchyma: It is made up of elongated, tapering
- Primary xylem is 2 types: cylindrical cells which have dense cytoplasm and nucleus.
o Protoxylem: The first formed primary xylem. The cell wall is composed of cellulose and has pits through
o Metaxylem: The later formed primary xylem. which plasmodesmatal connections exist between the cells.
- In stems, the protoxylem lies towards the centre (pith) and Phloem parenchyma is absent in most of the monocots.
the metaxylem lies towards the periphery of the organ. This Function: It stores food material and other substances like
type of primary xylem is called endarch. resins, latex and mucilage.
- In roots, the protoxylem lies towards periphery and o Phloem fibres (bast fibres): These are made up of
metaxylem lies towards the centre. Such arrangement of sclerenchymatous cells. Generally absent in primary
primary xylem is called exarch. phloem but are found in the secondary phloem. These are
b. Phloem (Bast) much elongated, unbranched and have pointed, needle like
It transports food materials from leaves to other parts. apices. Cell wall is quite thick. At maturity, these fibres
In angiosperms, phloem is composed of sieve tube elements, lose their protoplasm and become dead. Phloem fibres of
companion cells, phloem parenchyma & phloem fibres. jute, flax and hemp are used commercially.
Gymnosperms have albuminous cells and sieve cells. They Function: Mechanical support & protection to soft tissues.
lack sieve tubes and companion cells.
THE TISSUE SYSTEM
Based on structure and location, tissue systems are 3 types: Stomata
o Epidermal tissue system - These are structures present in the epidermis of leaves.
o Ground (fundamental) tissue system - Stomata regulate the transpiration and gaseous exchange.
o Vascular (conducting) tissue system - A stoma is made of two bean-shaped cells (guard cells).
1. Epidermal Tissue System - In grasses, the guard cells are dumbbell shaped.
- It forms the outer-most covering of the whole plant body.
- It comprises epidermal cells, stomata and epidermal
appendages (trichomes & hairs).
Epidermis
- It is the outermost layer of the primary plant body.
- Epidermis is usually single layered. - The outer walls of guard cells (away from the stomatal
- It is made up of elongated, compactly arranged pore) are thin and the inner walls (towards the stomatal
parenchymatous cells with a small amount of cytoplasm pore) are highly thickened.
lining the cell wall and a large vacuole. - The guard cells possess chloroplasts and regulate the
- The outside of the epidermis is often covered with a waxy opening and closing of stomata.
thick layer (cuticle). It prevents the loss of water. Cuticle - Sometimes, a few epidermal cells near the guard cells
is absent in roots. become specialized in their shape and size. They are
known as subsidiary cells.
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