Anatomy of monocot and dicot roots – Primary structure of monocotyledonous root

Anatomy of monocot and dicot roots – Primary structure of monocotyledonous root

Back to botany topic list

The embryo develops into an adult plant with roots, stem and leaves due to the activity of the apical meristem.

A mature plant has three kinds of tissue systems – the dermal, the fundamental and the vascular system.

The dermal system includes the epidermis, which is the primary outer protective covering of the plant body.

The periderm is another protective tissue that supplants the epidermis in the roots and stems that undergo secondary growth.

The fundamental tissue system includes tissues that form the ground substance of the plant in which other permanent tissues are found embedded.

Parenchyma, collenchyma and sclerenchyma are the main ground tissues.

The vascular system contains the two conducting tissues, the phloem and xylem.

In different parts of the plants, the various tissues are distributed in characteristic patterns.

This is best understood by studying their internal structure by cutting sections (transverse or longitudinal or both) of the part to be studied.

Primary structure of monocotyledonous root – Maize root

The internal structure of the monocot roots shows the following tissue systems from the periphery to the centre.

They are epiblema or rhizodermis, cortex and stele.

Rhizodermis or epiblema

It is the outermost layer of the root. It consists of a single row of thin-walled parenchymatous cells without any intercellular space.

Stomata and cuticle are absent in the rhizodermis. Root hairs that are found in the rhizodermis are always unicellular.

They absorb water and mineral salts from the soil. Root hairs are generally short lived.

The main function of rhizodermis is protection of the inner tissues.

Cortex

The cortex is homogenous. i.e. the cortex is made up of only one type of tissue called parenchyma.

It consists of many layers of thin-walled parenchyma cells with lot of intercellular spaces.

The function of cortical cells is storage. Cortical cells are generally oval or rounded in shape.

Chloroplasts are absent in the cortical cells, but they store starch. The cells are living and possess leucoplasts.

The inner most layer of the cortex is endodermis. It is composed of single layer of barrel shaped parenchymatous cells.

This forms a complete ring around the stele. There is a band like structure made of suberin present in the radial and transverse walls of the endodermal cells.

They are called Casparian strips named after Casparay who first noted the strips.

The endodermal cells, which are opposite to the protoxylem elements, are thin-walled without casparian strips.

These cells are called passage cells. Their function is to transport water and dissolved salts from the cortex to the xylem.

Water cannot pass through other endodermal cells due to casparian strips.

The main function of casparian strips in the endodermal cells is to prevent the re-entry of water into the cortex once water entered the xylem tissue.

Stele

All the tissues inside the endodermis comprise the stele. This includes pericycle, vascular system and pith.

Pericycle

Pericycle is the outermost layer of the stele and lies inner to the endodermis. It consists of a single layer of parenchymatous cells.

Vascular System

Vascular tissues are seen in radial arrangement. The number of protoxylem groups is many.

This arrangement of xylem is called polyarch. Xylem is in exarch condition.

The tissue, which is present between the xylem and the phloem, is called conjunctive tissue. In maize, the conjunctive tissue is made up of sclerenchymatous tissue.

Pith

The central portion is occupied by a large pith. It consists of thin-walled parenchyma cells with intercellular spaces.

These cells are filled with abundant starch grains.

Back to botany topic list

Describe the primary structure of a monocot root.

Explain briefly about Primary structure of monocotyledonous root – Maize root.

Draw and label the parts of transverse section of monocot root.

For more detail about monocotyledonous root  click here

Other links 

Plant anatomy – Meristematic tissue

---

Permanent tissue , simple tissue characteristics

---

Complex tissues , Xylem and its Kinds

---

Phloem and its Kinds

---

Tissue system – Epidermal,Vascular and fundamental tissue system

---

 

Structure of dicotyledonous root – Bean root

---

Anatomy of monocot stem – Maize stem

---

Primary structure of dicotyledonous stem – Sunflower stem

---

Anatomy of a dicot and monocot leaves

 

Tissue system – epidermal tissue system and Functions, Vascular tissue system

Tissue system – epidermal tissue system and Functions, Vascular-tissue-system

Back to botany topic list

The tissue system

A group of tissues performing a similar function irrespective of its position in the plant body is called a tissue system.

In 1875, Sachs recognized three tissue systems in the plants.

They are epidermal tissue system, vascular tissue system and fundamental tissue system.

Epidermal tissue system

Epidermal tissue system is the outermost covering of plants.

It consists of epidermis, stomata and epidermal outgrowths.

Epidermis is generally composed of single layer of parenchymatous cells compactly arranged without intercellular spaces.

But it is interrupted by stomata. In leaves some specialized cells which surround the stomata are called the guard cells.

Chloroplasts are present only in the guard cells of the epidermis. Other epidermal cells usually do not have chloroplasts.

The outer wall of epidermis is usually covered by cuticle.

Stoma is a minute pore surrounded by two guard cells.

The stomata occur mainly in the epidermis of leaves. In some plants such as sugarcane, the guard cells are bounded by some special cells.

They are distinct from other epidermal cells. These cells are called subsidiary or accessory cells.

Trichomes and root hairs are some epidermal outgrowths. The unicellular or multicellular appendages that originate from the epidermal cells are called trichomes.

Trichomes may be branched or unbranched. Rhizodermis has two types of epidermal cells – long cells and short cells.

The short cells are called trichoblasts. Root hairs are produced from these trichoblasts.

Functions of epidermal tissue system

1. This tissue system in the shoot checks excessive loss of water due to the presence of cuticle.

2. Epidermis protects the underlying tissues.

3. Stomata involve in transpiration and gaseous exchange.

4. Trichomes are also helpful in the dispersal of seeds and fruits.

5. Root hairs absorb water and mineral salts from the soil.

Vascular tissue system

The vascular tissue system consists of xylem and phloem. The elements of xylem and phloem are always organized in groups.

They are called vascular bundles. In dicot stem, the vascular bundle consists of cambial tissue in between xylem and phloem.

Such vascular bundle is called open vascular bundle. In monocot stem, cambium is absent in the vascular bundle, hence it is known as closed vascular bundle

In roots, xylem and phloem are arranged in an alternate manner on different radii.

It is called radial arrangement. In stems and leaves, xylem and phloem are arranged at the same radius and form a vascular bundle together.

Such vascular bundle is called conjoint vascular bundle. Depending upon the mutual relationship of xylem and phloem, conjoint vascular bundles are divided into three types.

They are collateral, bicollateral and concentric.

If xylem and phloem in a vascular bundle are arranged along the same radius with phloem towards the outside, such vascular bundle is called collateral vascular bundle.

If phloem occurs on both the outer and inner sides of xylem, the bundle is called bicollateral.

Bicollateral vascular bundles are most typically seen in Cucurbitaceae.

The bundle in which either phloem surrounds the xylem or xylem surrounds the phloem completely is known as concentric vascular bundle.

This is of two types amphicribral and amphivasal. In amphicribral concentric vascular bundles, the phloem completely surrounds the xylem. eg. Polypodium.

In amphivasal concentric vascular bundles, the xylem completely surrounds the phloem. eg. Acorus.

In roots, protoxylem vessels are present towards the periphery and the metaxylem vessels towards the centre. This arrangement of xylem is called exarch.

In stem, protoxylem vessels are towards the centre, while metaxylem towards the periphery. This condition is known as endarch.

Ground or fundamental tissue system

The ground or fundamental tissue system constitutes the main body of the plants.

It includes all the tissues except epidermis and vascular bundles.

In monocot stem, ground tissue system is a continuous mass of parenchymatous tissue in which vascular bundles are found scattered.

Here ground tissue is not differentiated into cortex, endodermis, pericycle and pith.

Generally in dicot stem, ground tissue system is differentiated into three main zones – cortex, pericycle and pith.

The cortex occurs between the epidermis and pericycle. Cortex may be a few to many layers in thickness.

In most cases, cortex is made up of parenchyma tissues. Intercellular spaces may or may not be present.

Cortical cells may contain non-living inclusions like starch grains, oils, tannins and crystal.

In the leaves, the ground tissue consists of chlorenchyma tissues. This region is called mesophyll.

The inner most layer of the cortex is called endodermis. Generally endodermis is made up of barrel shaped parenchyma cells.

These cells are arranged in a single layer without intercellular spaces.

Pericycle occurs between the endodermis and the vascular bundles. It is generally made up of parenchyma cells.

Lateral roots originate from the pericycle. Thus their origin is endogenous.

The central part of the ground tissue is known as pith or medulla. Generally this is made up of thin walled parenchyma cells which may be with or without intercellular spaces.

The cells in the pith generally store starch, fatty substances, tannins, phenols, calcium oxalate crystals, etc.

Back to botany topic list

For more details about epidermal tissue system Click Here 

Click here for more details about vascular tissue system

Other links 

Plant anatomy – Meristematic tissue

---

Permanent tissue , simple tissue characteristics

---

Complex tissues , Xylem and its Kinds

---

Phloem and its Kinds

---

 

Primary structure of monocotyledonous root – Maize root

---

Structure of dicotyledonous root – Bean root

---

Anatomy of monocot stem – Maize stem

---

Primary structure of dicotyledonous stem – Sunflower stem

---

Anatomy of a dicot and monocot leaves

 

Phloem and its Kinds – Sieve elements , Companion cells , Phloem parenchyma , Phloem fibres

Phloem and its Kinds ( Sieve elements , Companion cells , Phloem parenchyma , Phloem fibres )

Back to botany topic list

Phloem

Like xylem, phloem is also a complex tissue. It conducts food materials to various parts of the plant.

The phloem elements which are formed from the procambium of apical meristem are called primary phloem.

The phloem elements which are produced by the vascular cambium are called secondary phloem.

The primary phloem elements that develop first from the procambium are smaller in size called the protophloem, whereas those develop later are larger in size called metaphloem.

The protophloem is short lived. It is crushed by the developing metaphloem.

Phloem tissue

Phloem is composed of four kinds of cells: sieve elements, companion cells,phloem parenchyma and phloem fibres.

Companion cells are present only in angiosperms.

Companion cells are absent in pteridophytes and gymnosperms.

Phloem fibres are absent in the primary phloem of most of the angiosperms. But they are usually present in the secondary phloem.

Sieve elements

Sieve elements are the conducting elements of the phloem. They have thick primary walls.

Their end walls are transverse or oblique. The end wall contains a number of pores and it looks like a sieve. So it is called a sieve plate.

The sieve elements are arranged one above the other and form vertical sieve tubes. In matured sieve tube, nucleus is absent.

It contains a lining layer of cytoplasm. This is an important feature of sieve elements. A special protein called slime body is seen in it.

The conduction of food material takes place through cytoplasmic strands. They are distinguished into sieve cells and sieve tubes.

Sieve cells occur in pteridophytes and gymnosperms, while sieve tubes occur in angiosperms.

Sieve cells have sieve areas on their lateral walls only and are not arranged one above the other in linear rows.

They are not associated with companion cells. Sieve tubes are arranged one above the other in linear rows and have sieve plates on their end walls.

They are associated with the companion cells.

In mature sieve elements, sometimes the pores in the sieve plate are blocked by a substance called cellose.

Companion cells

The thin-walled, elongated, specialised parenchyma cells, which are associated with the sieve elements, are called companion cells.

In contrast to sieve elements, the companion cells have cytoplasm and a prominent nucleus.

They are connected to the sieve tubes through pits found in the lateral walls.

The companion cells are present only in angiosperms and absent in gymnosperms and pteridophytes.

They assist the sieve tubes in the conduction of food materials.

Phloem parenchyma

The parenchyma cells associated with the phloem are called phloem parenchyma.

These are living cells. They store starch and fats. Phloem parenchyma also contain resins and tannins in some plants.

They are present in all , pteridophytes, gymnosperms and dicots. In monocots, usually phloem parenchyma is absent.

Phloem fibres

The fibres of sclerenchyma associated with phloem are called phloem fibres or bast fibres.

They are narrow, vertically elongated cells with very thick walls and a small lumen (the cell cavity).

Among the four kinds of phloem elements, phloem fibres are the only dead tissue.

These are the strengthening and supporting cells.

Back to botany topic list

Click Here for more information

Other links 

Plant anatomy – Meristematic tissue

---

Permanent tissue , simple tissue characteristics

---

Complex tissues , Xylem and its Kinds

---

 

Tissue system – Epidermal,Vascular and fundamental tissue system

---

Primary structure of monocotyledonous root – Maize root

---

Structure of dicotyledonous root – Bean root

---

Anatomy of monocot stem – Maize stem

---

Primary structure of dicotyledonous stem – Sunflower stem

---

Anatomy of a dicot and monocot leaves

 

Complex tissues , Xylem and its Kinds

Complex tissues , Xylem and its Kinds

Back to botany topic list

Complex tissues

A tissue that consists of several kinds of cells but all of them function together as a single unit is called complex tissue. It is of two types – xylem and phloem.

Xylem

Xylem (Greek word ‘xylos’= wood) is a complex tissue that is mainly responsible for the conduction of water and mineral salts from roots to other parts of the plant.

The xylem, which is derived from procambium, is called primary xylem and the xylem, which is derived from vascular cambium, is called secondary xylem.

Earlier formed xylem elements are called protoxylem, whereas the later formed xylem elements are calledmetaxylem.

Xylem is made up of four kinds of cells – tracheids, vessels or tracheae, xylem fibres and xylem parenchyma.

Tracheids

Tracheids are elongated with blunt ends. Its lumen is broader than that of fibres. Their secondary wall is lignified.

In cross section, the tracheids appear polygonal and thick walled. The pits are simple or bordered.

There are different types of cell wall thickening due to deposition of secondary wall substances.

They are annular (ring like), spiral (spring like), scalariform (ladder like), reticulate (net like) and pitted (uniformly thick except at pits).

Tracheids are imperforate cells with bordered pits on their end walls. They are arranged one above the other.

Tracheids are chief water conducting elements in gymnosperms and pteridophytes. Here, the conduction of water and mineral salts takes place through the bordered pits.

They also offer mechanical support to the plants.

Vessels or Tracheae

Vessels are perforated at the end walls. Its lumen is wider than that of tracheids. The perforated plates at the end wall separate the vessels.

They occur parallel to the long axis of the plant body. Due to dissolution of entire end wall, a single pore is formed at the perforation plate.

It is called simple perforation plate eg. Mangifera. If the perforation plate has many pores, then it is called multiple perforation plate.

eg. Liriodendron.

The secondary wall thickenings of vessels are annular, spiral, scalariform, reticulate, or pitted as in tracheids.

Vessels are chief water conducting elements in angiosperms and they are absent in pteridophytes and gymnosperms.

However, in Gnetum of gymnosperms, vessels oc¬cur. The main function of vessel is conduction of water and minerals.

It also offers mechanical strength to the plant.

kinds of xylem cells

Xylem fibres

The fibres of sclerenchyma associated with the xylem are known as xylem fibres. They give additional mechanical support to the plant body.

They are present both in primary and secondary xylem. Xylem fibres are dead cells and have lignified walls with narrow lumen.

This xylem fibres are also called libriform fibres.

Xylem parenchyma

The parenchyma cells associated with the xylem are known as xylem parenchyma.

Xylem parenchyma is the only living tissue amongst the consituents of xylem. The cell wall is thin and made up of cellulose.

The xylem parenchyma cells store food reserves in the form of starch and fat. They also assist in conduction of water.

Back to botany topic list

For more details click here

Other links 

Plant anatomy – Meristematic tissue

---

Permanent tissue , simple tissue characteristics

---

 

Phloem and its Kinds

---

Tissue system – Epidermal,Vascular and fundamental tissue system

---

Primary structure of monocotyledonous root – Maize root

---

Structure of dicotyledonous root – Bean root

---

Anatomy of monocot stem – Maize stem

---

Primary structure of dicotyledonous stem – Sunflower stem

---

Anatomy of a dicot and monocot leaves

 

Classification of permanent tissue and simple tissue with characteristics

Permanent tissue and simple tissue and its characteristics

Back to botany topic list

Permanent tissue

The cells, which are formed by apical meristem, are differentiated into different types of permanent tissues. These tissues have lost the power of dividing either permanently or temporarily.

Classification of permanent tissue

Based on the constituent cells, the permanent tissue is classified into two types – simple tissue and complex tissue.

Simple tissue

A tissue with the cells of similar structure and function is called simple tissue. It is of three types – parenchyma, collenchyma and sclerenchyma.

Parenchyma

It is generally present in all organs of the plant. It constitutes the ground tissue in a plant. Parenchyma is the precursor of all the other tissues.

Parenchyma is a living tissue and made up of thin walled cells. The cell wall is made up of cellulose.

Parenchyma cells may be oval, spherical, rectangular, cylindrical or stellate.

The cells are usually polyhedral with 10 to12 facets. Parenchyma is of different types and some of them are discussed as follows.

In water plants, the parenchyma found in the cortex region possesses well-developed large intercellular spaces called air spaces.

This air filled parenchyma tissue is called aerenchyma. It helps the plant to float in water. eg. Nymphaea and Hydrilla.

The parenchyma cells that are stored with starch grains are called storage parenchyma. eg. stem and root tubers.

In the petioles of banana and Canna, star shaped parenchyma cells are found. These cells are called stellate parenchyma.

In green parts of the plants, the parenchymatous cells have chloroplasts.

These cells are called chlorenchyma. Its important function is photosynthesis.

Collenchyma

Collenchyma generally occurs in the dicot stems in two or more layers below the epidermis.

These layers constitute the hypodermis. It is absent in the roots of land plants. Collenchyma also occurs in petiole and pedicel.

It gives strength to young organs. Collenchyma is a living tissue. It consists of more or less elongated cells, which are polygonal in cross section.

The cell wall is unevenly thickened. The thickening is confined to the corners of the cells.

Besides cellulose, the cell wall contains high amounts of hemicellulose and pectin.

Collenchyma may contain chloroplasts and carry out photosynthesis.

Collenchyma is divided into three types –

lamellar, angular and lacunate collenchyma

In the hypodermis of Helianthus, only the tangential walls of collenchyma are thickened and the radial walls are devoid of thickening.

This type of collenchyma is called lamellar collenchyma. In the hypodermis of Datura and Nicotiana, the cell walls of collenchyma are thickened at their angles.

This type is called angular collenchyma. In the hypodermis of Ipomoea, the cell wall thickening materials are deposited on the walls bordering the intercellular spaces.

This type is called lacunate collenchyma.

Sclerenchyma

Sclerenchyma is a dead tissue. The cells have lignified secondary walls. They lack protoplasts.

On the basis of origin, structure and function, sclerenchyma is divided into two types – sclereids and fibres.

The sclereids are different from fibres in the following respects.

Sclereids are shorter whereas fibres are longer sclereids possess numerous pits as compared to the fibres.

Sclereids

The Sclereids are dead cells. They vary greatly in shape and thickness. The cell wall is very thick due to lignification. Lumen is very much reduced.

The pits may be simple or branched. Usually sclereids are isodiametric, but in some plants they are elongated.

They are responsible for the rigidity of the seed-coat. The isodiametric sclereids are called brachy-sclereids (stone cells).

They are found in bark, pith, cortex, hard endocarp and fleshy portions of some fruits. eg. pulp of Pyrus.
Elongated rod shaped sclereids are called macrosclereids (rod cells).

They are found in the outer seed coat. eg. Crotalaria. The rod shaped sclereids with dilated ends are called osteosclereids (bone cells).

eg. seed coat of Pisum.

Types of sclerenchyma

Fibres

Fibre cells are dead cells. They are very long and narrow with pointed ends. In transverse section, the fibres are polygonal with narrow lumen.

The secondary wall is evenly thickened with lignin. It possesses simple pits. Fibres are supporting tissues.

They provide mechanical strength to the plants and protect them from the strong winds.

The fibres that are found in the seed coat of some seeds are called surface fibres. eg. cotton.

Back to botany topic list

Define a permanent tissue.

What are the types of simple tissues and complex tissues?

What is a stellate parenchyma?

What is a chlorenchyma?

Differentiate angular collenchyma from lacunate collenchyma.

Write an essay on the location, structure and functions of
parenchyma.

Describe the location, structure and functions of collenchyma.

Give an account on sclerenchyma.

Other links 

Plant anatomy – Meristematic tissue

---

 

Complex tissues , Xylem and its Kinds

---

Phloem and its Kinds

---

Tissue system – Epidermal,Vascular and fundamental tissue system

---

Primary structure of monocotyledonous root – Maize root

---

Structure of dicotyledonous root – Bean root

---

Anatomy of monocot stem – Maize stem

---

Primary structure of dicotyledonous stem – Sunflower stem

---

Anatomy of a dicot and monocot leaves

 

Meristematic tissue

Plant anatomy – tissue and tissue system – meristematic

Back to botany topic list

Plant anatomy

(Ana = as under, tamnein = to cut) is the study of internal structure and organization of plants, especially of their parts by means of dissection and microscopic examination.

The simple type of plant body is unicellular. In such forms, the single cell performs all the vital functions of life.

It grows, prepares food, undergoes metabolism, reproduces and completes its span of life.

The progressive evolution in plants has resulted in increasing complexity of structures.

In higher plants, root, stem, leaves and flowers carry out different functions.

Due to these divisions of labour, the cells of the plant are differentiated to form different tissues.

Tissues and tissue systems meristematic

The study of internal structure of plants reveals many types of tissues.

Morphologically, a tissue is a group of cells, which are similar in origin, form and function.

Physiologically, a tissue is composed of dissimilar cells that perform a common function, for example, phloem elements and food conduction respectively.

The cells form various kinds of tissues. Two or more types of tissues form tissue systems.

Different tissue systems form the organs. Each tissue carries out a specific function. Tissues can be classified into two types –

Meristematic tissue

A meristematic tissue (meristos = divisible) is a group of identical cells that are in a continuous state of division.

Some cells produced by meristematic tissue stop dividing and acquire certain changes to become permanent tissues of the plant.

This change from meristematic to permanent tissue is called differentiation.

The remaining cells in the meristem retain their meristematic activity. Meristematic cells are self-perpetuating.

Characteristics of meristematic cells

The meristematic cells may be round, oval, polygonal or rectangular in shape.

They are closely arranged without intercellular spaces. Meristematic cells have dense cytoplasm with large nucleus.

They have smaller vacuoles, which are scattered throughout the cytoplasm.

Their cell walls are thin, elastic and made up of cellulose.

Classification of meristem

Based on its position, the meristem is divided into three types – apical meristem, intercalary meristem and lateral meristem.

Apical meristem

Apical meristem is found at the tips of roots, stem and branches. It is responsible for increase in length of plant.

It is divided into three zones – protoderm, procambium and ground meristem.

Protoderm gives rise to epidermal tissue; procambium gives rise to primary vascular tissues and ground meristem gives rise to cortex and pith.

Intercalary meristem

It is present in the nodal region and is prominently found in monocotyledons, eg. grasses.

As the name indicates, it is present in between the permanent tissues.

It is derived from the apical meristem and is responsible for the elongation of internodes.

Lateral meristem

The meristem that is present along the longitudinal axis of stem and root is called lateral meristem.

Vascular cambium and cork cambium (phellogen) are examples for lateral meristem.

It produces secondary permanent tissues, which result in the thickening of stem and root.

L.S of shoot – showing the positions of meristems

Back to botany topic list

For more information click here

Other links 

 

Permanent tissue , simple tissue characteristics

---

Complex tissues , Xylem and its Kinds

---

Phloem and its Kinds

---

Tissue system – Epidermal,Vascular and fundamental tissue system

---

Primary structure of monocotyledonous root – Maize root

---

Structure of dicotyledonous root – Bean root

---

Anatomy of monocot stem – Maize stem

---

Primary structure of dicotyledonous stem – Sunflower stem

---

Anatomy of a dicot and monocot leaves

 

Musaceae – Musa paradisiaca and its Economic Importance

Musaceae – Musa paradisiaca and its Economic Importance

Back to botany topic list

MONOCOT FAMILY

MUSACEAE – the banana family Systematic position

Class : Monocotyledonae
Series : Epigynae
Family : Musaceae

General characters – Musaceae

Distribution

Musaceae includes about 6 genera and about 150 species. The members of this family are widely distributed over tropical regions of the world.

In India it is represented by 2 genera and about 25 species.

Habit

Mostly perennial herbs attaining considerable height, perennating by means of rhizome (eg. Musa paradisiaca – Banana), rarely trees (eg. Ravenala madagascariensis – Traveller’s palm) and watery sap is present.

Root

Generally fibrous adventitious root system is seen.

Stem

In Musa the real stem is underground called rhizome.

The apparent, unbranched, errect and areal pseudostem is formed by the long, stiff and sheathy leaf bases which are rolled around one another to form an aerial pseudostem.

The central axis that is concealed at the bottom of the pseudostem is called shaft.

At the time of flowering, the shaft elongates, pierces through the pseudostem and produces an inflorescence terminally.

Musa is a monocorpic perennial, because it produces flowers and fruits once during its life time.

In Ravenala, the stem is aerial and woody.

Leaf

Simple with a long and strong petiole. The leaf blade is large and broad with sheathy leaf base.

The leaf is extipulate and obtuse. The pinnately parellel venation extends upto the leaf margin.

The phyllotaxy is spiral in Musa but in Ravenala it is distichous i.e. the leaves are arranged in two rows on the same sides.

Inflorescence

In Musa, the inflorescence is branced spadix.

The flowers are protected by large, brightly coloured, spirally arranged, boat shaped bracts called spathes.

When the flowers open, the spathes roll back and finally fall off. In Ravenalea, the inflorescence is a compound cyme.

In Musa, the flowers are polygamous i.e. staminate flowers, pistillate flowers and bisexual flowers are present in the same plant.

The male flowers lie within the upper bracts, the female flowers within the lower bracts and the bisexual flowers within the middle bracts.

Flowers

Brateate, ebractiolate, sessile, trimerous, unisexual or bisexual, when unisexual, the flowers are monoecious.

The flowers are zygomorphic and epigynous.

Perianth

Tepals 6, arranged in two whorls of 3 each, free or united.

In Musa, the three tepals of the outer whorl and the two lateral tepals of the inner whorl are fused by valvate aestivation to form 5 toothed tube like structure.

The inner posterior tepal is alone free. It is distinctly broad and membranous.

Androecium

Basically stamens 6, in two whorls of 3 each, arranged opposite to the tepals. In Musa only 5 stamens are fertile and the inner posterior stamen is either absent or represented by a staminode.

In Ravenala, all the 6 stamens are fertile. Anthers are dithecous and they dehisce by vertical slits.

The filament is filiform and rudimentary ovary or pistillode is often present in the male flower.

Gynoecium

Ovary inferior, tricarpellary, syncarpous, trilocular, numerous ovules on axile placentation.

The style is simple and filiform. The stigma is three lobed.

Fruit

An elongated fleshy berry without seeds eg. Musa and a capsule eg. Ravenala.

Seed:

Non – endospermous

Botanical description of Musa paradisiaca – Musaceae

Habit

Gignatic monocorpic perennial herb.

Root

Fibrous adventitious root system.

Stem

The real stem is underground called rhizome.

The apparent, unbranched, errect and areal pseudostem is formed by the long, stiff and sheathy leaf bases which are rolled around one another to form an aerial pseudostem.

The central axis that is concealed at the bottom of the pseudostem is called shaft.

At the time of flowering, the shaft elongates, pierces through the pseudostem and produces an inflorescence terminally.

Leaf

Simple with a long and strong petiole. The leaf blade is large and broad with sheathy leaf base.

The leaf is extipulate and obtuse. The pinnately parellel venation extends upto the leaf margin. The phyllotaxy is spiral.

Inflorescence

It is branced spadix.

The flowers are protected by large, brightly coloured, spirally arranged, boat shaped bracts called spathes.

When the flowers open, the spathes roll back and finally fall off.

Flowers

Brateate, ebractiolate, sessile, trimerous, unisexual or bisexual, when unisexual, the flowers are monoecious.

The flowers are zygomorphic and epigynous.

Perianth

Tepals 6, arranged in two whorls of 3 each. The three tepals of the outer whorl and the two lateral tepals of the inner whorl are fused by valvate aestivation to form 5 toothed tube like structure.

The inner posterior tepal is alone free. It is distinctly broad and membranous.

Androecium

Stamens 6, in two whorls of 3 each, arranged opposite to the tepals.

Only 5 stamens are fertile and the inner posterior stamen is either absent or represented by a staminode.

Anthers are dithecous and they dehisce by vertical slits.

The filament is filiform and rudimentary ovary or pistillode is often present in the male flower.

Gynoecium

Ovary inferior, tricarpellary, syncarpous, trilocular, numerous ovules on axile placentation.

The style is simple and filiform. The stigma is three lobed.

Fruit

An elongated fleshy berry and the seeds are not produced in cultivated varities.
Floral formulae
Male flower .. Br., Ebrl., , , P(3+2)+1, A 3+3 , G 0.
0
Female flower .. Br., Ebrl., , , P(3+2)+1, A 0, G(3).
~
Bisexual flower .. Br., Ebrl., , , P(3+2)+1, A 3+3, G(3).

ECONOMIC IMPORTANCE Musaceae

1. Food plants

The fruits of Musa paradisiaca (Banana) are edible.

The tender green bananas, the shaft and the flowers are cooked and eaten as vegetable.

The leaves are commonly used as plates on festive occassions.

The sap obtained from the sheathy leaf bases is considered to be an antidote for cobra bite.

The small fruits obtained from Musa chinensis (Dwarf banana) are sweet and edible.

2. Fibre plant

The fibres obtained from sheathy leaf bases of Musa textilis (Manila hemp) are woven into Abaca cloth and used for cordage.

It is also known as Manila hemp. This plant is extensively grown in Philippines.

3. Ornamental plants

Ravenala madagascariensis (Traveller’s palm), Strelitzia reginae (the bird of paradise flower) and Heliconia sp. are grown as ornamentals.

Back to botany topic list

QUESTION

1. What is polygamous ? Give an example.
2. What is monocorpic perennial ? Give an example
3. Write the systematic position of musaceae
4. Explain the gynoecium of Musa paradisiaca,.
5. Draw the floral diagram of bisexual flower of Musa paradisiaca and write floral formula.
6. What is pseudostem? How is it formed in Musa paradisiaca ?
7. List out the economic importance of Musa paradisiaca.
8. Write the differences between Musa and Ravenala.
9. Describe the androecium and gynoecium of Musa paradisiaca.
10. Write the economic importance of members of musaceae.
11. Describe Musa paradisiaca  in technical terms.
12. Write the general characteristic features of Musaceae

For more details click here

Other links 

TAXONOMY OF ANGIOSPERMS, TYPES OF CLASSIFICATION

---

BIOSYSTEMATICS NOMENCLATURE

---

BINOMIAL NOMENCLATURE, ICBN

---

HERBARIA AND ITS USES IMPORTANCE OF HERBARIUM

---

Bentham and Hooker’s classification of plants

---

Dicot Families – MALVACEAE

---

Botanical description of Hibiscus and Economical importance of Malvaceae

---

Solanaceae – Datura metal and Economic importance

---

Euphorbiaceae and Ricinus communis and its Economic importance

---

 

Euphorbiaceae – Ricinus communis and its Economic importance

Euphorbiaceae and Ricinus communis and its Economic importance

Back to botany topic list

EUPHORBIACEAE – the castor family

Systematic position
Class: Dicotyledonae
Sub-class: Monochlamydeae
Series: Unisexuales
Family: Euphorbiaceae

General characters of Euphorbiaceae

Distribution 

Euphorbiaceae includes more than 300 genera and about 7,500 species.

It is world wide in distribution, but particularly well represented in Africa and South America.

In India, it is represented by more than 70 genera and about 450 species.

Habit

This family includes a large number of annual herbs (eg. Phyllanthus amarus) or shrubs (eg. Ricinus communis) or trees (eg. Phyllanthus emblica).

In several species of Euphorbia, the stem is modified to perform photosynthesis.

This modified stem is called cladode and it resembles cactus.

eg. E. tirucalli and E. antiquorum (Sadhurakkalli).

This family shows a great range of variation in vegetative and floral characters.

Almost all the plants have latex which is either milky or watery.

Root

A branched tap root system.

Stem Aerial, erect or prostrate (eg. E. prostrata), cylindrical, branched, solid or hollow (eg. Ricinus communis), usually contains milky latex (eg. E. tirucalli) or watery latex (eg. Jatropha curcas).

Leaf

Stipulate or exstipulate, petiolate, alternate (eg. Ricinus communis), simple, entire or deeply lobed or trifoliately compound (eg. Hevea brasiliensis) and with unicostate or multicostate reticulate venation.

The stipules are modified into a pair of spines (eg. E.splendens) or glandular hairs (eg. Jatropha curcas). In xerophytic species of Euphorbia, leaves are reduced or absent.

The leaves around the cyathium become beautifully coloured in E. pulcherrima (Paalperukki tree).

Inflorescence

The characteristic inflorescence of Euphorbia is cyathium.

It is a collection of unisexual flowers arranged in cymose manner on a condensed axis and enclosed within a cup-shaped involucre.

Each cyathium has a single central female flower surrounded by two to many male flowers.

Each male flower is represented by a single stamen. They are arranged in centrifugal manner.

The pedicel in female flower is short or long.

If it is short, the female flower remains hidden within the involucre. If it is long, the female flower comes out of involucre.

Extra floral nectar secreting gland is also located in the cyathium.
Various types of inflorescence are seen in the members of Euphorbiaceae.

In Ricinus communis, it is a panicle where female and male flowers are arranged in racemose manner.

Female flowers are at the top and male flowers below. In Croton sparsiflorus (Eli amanakku), the inflorescence is simple raceme, whereas in Acalypha indica (Kuppaimeni), it is catkin.

In Phyllanthus amarus, the male and female flowers are axillary and solitary.

Flower

Bracteate, ebracteolate, pedicellate, unisexual, monoecious or dioecious, incomplete and hypogynous.

In Euphorbia , the male flower is represented by a single stamen and female flower by a single pistil.

Perianth

In Croton sparsiflorus, the male flowers have two whorls of perianth whereas the female flowers have a single whorl of perianth.

The male and female flowers of Euphorbia are usually devoid of perianth i.e aphyllous.

The tepals are polyphyllous in Phyllanthus amarus and gamophyllous in Ricinus communis.

Androecium

Stamen one to many, free or united. In Ricinus communis, the stamen is polyadelphous and the filaments are branched.

They are fused into several bundles. Anthers are dithecous. Rudimentary ovary called pistillode is often present in male flowers.

Gynoecium

Ovary superior, tricarpellary and syncarpous.

The ovary trilocular with one or two ovules in each locule on axile placentation.

Ovary is distinctly three lobed. Styles three, each ending in a bifid stigma.

Fruit

Most commonly schizocarpic capsule or drupe.

It is regma in Ricinus communis, dehiscing into three cocci.

Seed

Endospermous.

 

Botanical description of Ricinus communis – Euphorbiaceae

Habit

Perennial shrub.

Root

Branched tap root system.

Stem

Aerial, erect, herbaceaous but woody below, branched and hollow. Young branches are covered with hair like outgrowth. Latex is present.

Leaf

Petiolate, exstipulate, alternate, deeply palmately lobed with 7 or more lobes. Venation is palmately reticulate divergent.

Inflorescence

Compound raceme or panicle and terminal. Male flowers are seen below and female flowers near the apex.

Male Flower

Bracteate, ebracteolate, pedicellate, actinomorphic and incomplete.

Perianth

Tepals 5, arranged in single whorl, gamophyllous, valvate aestivation and odd tepal is posterior in position.

Androecium

Stamens many, polyadelphous, filaments branched and united to form five branches.

Anthers are dithecous, globose, basifixed, introrse and dehiscing by longitudinal slits.

Gynoecium

Absent but pistillode is present. Floral Formula
Br., Ebrl., ⊕, , P(5), A∝, G0. Female Flower
Bracteate, ebracteolate, pedicellate, actinomorphic, incomplete and hypogynous.

Perianth

Tepals 3 arranged in single whorl and gamophyllous showing valvate aestivation.

Androecium

Absent but staminode is present.

Gynoecium

The ovary superior, tricarpellary and syncarpous.

Ovary trilocular with one ovule in each locule on axile placentation.

Styles 3, deep red and long. Bifid with feathery stigma.

Fruit

Fruit is called regma. It is covered by spinous outgrowths.

The fruit splits into three one seeded cocci.

Seed

Endospermous
Floral Formula
Br., Ebrl.,⊕, , P (3), A 0, G (3).

ECONOMIC IMPORTANCE of Euphorbiaceae

1. Food plants

The tuberous root of Manihot esculenta (tapioca) is rich in starch and forms valuable food stuff.

The fleshy fruits of Phyllanthus emblica (Gooseberry) are rich in vitamin C. The fruit is edible and pickled.

2. Oil plants

Castor oil extracted from the seeds of Ricinus communis (Castor) is used as lubricant, vegetable oil and purgative.

Jatropha oil obtained from the seeds of Jatropha curcas (Kattamanakku) is used as purgative, to treat skin diseases and to extract bio-diesel.

3. Medicinal plants

The entire shoot system of Phyllanthus amarus (Keezhanelli) is used to treat jaundice.

The leaves and roots of Jatropha gossypifolia are used in the treatment of leprosy and snakebite.

4. Rubber plants

Over 98% of total natural rubber produced in the world is obtained from the coagulated latex of Hevea brasiliensis (para rubber) and Manihot glaziovii (manicoba rubber).

5. Ornamental plants

Euphorbia pulcherrima, Codiaeum variegatum (croton of gardens), E. tirucalli (milk bush) are examples for ornamental plants.

Back to botany topic list

QUESTION of Euphorbiaceae:

1. Write the systematic position of Euphorbiaceae.
2. What is cladode? Give an example
3. What are different types of inflorescence seen in Euphorbiaceae? Give example for each.
4. Mention the binomials of two rubber plants of Euphorbiaceae
5. Describe the inflorescence of Ricinus
6. Describe the cyathium inflorescence.
7. Give an account of  the  general  characteristic  features  of Euphorbiaceae.
8. Describe the male flower of Ricinus communis.
9. Describe the female flower of Ricinus
10. Write a brief account on different types of inflorescences of Euphorbiaceae.
11. Write a detailed  account  on  the  economic importance  of Euphorbiaceae.
12. Describe Ricinus communis in botanical terms.

For more Click here about euphorbiaceae

Other links 

TAXONOMY OF ANGIOSPERMS, TYPES OF CLASSIFICATION

---

BIOSYSTEMATICS NOMENCLATURE

---

BINOMIAL NOMENCLATURE, ICBN

---

HERBARIA AND ITS USES IMPORTANCE OF HERBARIUM

---

Bentham and Hooker’s classification of plants

---

Dicot Families – MALVACEAE

---

Botanical description of Hibiscus and Economical importance of Malvaceae

---

Solanaceae – Datura metal and Economic importance

---

 

Musaceae – Musa paradisiaca and its Economic Importance

Solanaceae – Datura metal and Economic importance

Solanaceae – Datura metal and Economic importance

Back to botany topic list

SOLANACEAE – the potato family

Systematic position
Class: Dicotyledonae
Sub-class: Gamopetalae
Series: Bicarpellatae
Order: Polemoniales
Family: Solanaceae

General Characters Solanaceae

Distribution

Solanaceae includes about 90 genera and more than 2,800 species. The plants are widely distributed in tropical and subtropical regions.

In India, this family is represented by 21 genera and 70 species.

Habit

Mostly annual herbs (eg. Solanum melongena), a few shrubs eg. Solanum tormm (Sundaikaai) and rarely trees (S. giganteum).

Root

A branched tap root system.

Stem

Aerial, erect, spinous eg. Solanum xanthocarpum (Kandangkathiri), herbaceous, woody, cylindrical, branched, hairy (eg. Petunia hybrida and Nicotiana alata). In S. tuberosum, the stem is modified into tuber.

Leaf

Petiolate, usually alternate, sometimes opposite, simple, entire (eg. Petunia hybrida), exstipulate and showing unicostate reticulate venation.

In S. xanthocarpum, the midrib and veins are found with yellowish spines.

Inflorescence

Solitary, axillary cyme (eg. Datura stramonium) or extra axillary scorpioid cyme called rhipidium (fan shaped cyme) as in S. nigrum or helicoid cyme as in S. tuberosum or umbellate cyme as in Withania somnifera.

 

Flower

Bracteate (eg. Petunia hybrida) or ebracteate

eg. S. nigrum (Manathakkaali), ebracteolate, pedicellate, dichlamydeous, pentamerous, complete, actinomorphic (eg. Datura stramonium) or Zygomorphic (eg. Schizanthus pinnatus), bisexual and hypogynous.

Calyx

Sepals 5, green, gamosepalous, tubular and showing valvate aestivation

eg. Datura metal (Oomathai) or imbricate aestivation (eg. Petunia hybrida), bell shaped and persistent (S. melongena).

Corolla

Petals 5, gamopetalous, funnel shaped, rotate, tubular, usually plicate (folded like a fan blade) showing twisted or valvate or imbricate aestivation.

Androecium Stamens 5, epipetalous, alternate with the petals, usually not equal in length and filaments are inserted in the middle or basal region of corolla tube and basifixed.

Anthers dithecous, introrse, usually basifixed or dorsifixed, dehiscing longitudinally or through apical pores (eg. S.nigrum).

In Schizanthus pinnatus, two stamens are fertile and three stamens are reduced to staminodes.

Gynoecium

Ovary superior, bicarpellary and syncarpous. Ovary bilocular, carpels obliquely placed and ovules on axile placentation.

In Datura species, bilocule becomes tetralocular by the formation of false septa. Style simple and undivided. Stigma bifid or capitate.

Fruit

A berry or septicidal capsule. In Lycopersicon esculentum, the fruit is a berry and in species of Datura and Petunia, the fruit is a capsule.

Seed

Endospermous.

Botanical description of Datura metal – Solanaceae

Habit

Large, erect and stout herb.

Root

Branched tap root system.

Stem

The stem is hollow, green and herbaceous with strong odour.

Leaf

Simple, alternate, petiolate, entire or deeply lobed, glabrous showing unicostate reticulate venation and exstipulate.

Inflorescence

Solitary and axillary cyme.

Flower

Flowers are large, greenish white, bracteate, ebracteolate, pedicellate, complete, dichlamydeous, pentamerous, regular, actinomorphic, bisexual and hypogynous.

Calyx

Sepals 5, green, gamosepalous showing valvate aestivation. Calyx is mostly persistent and odd sepal is posterior in position.

Corolla

Petals 5, greenish white, gamopetalous, plicate (folded like a fan) showing twisted aestivation, funnel shaped with wide mouth and 10 lobed.

Androecium

Stamens 5, free from one another epipetalous, alternate the petals and are inserted in the middle of the corolla tube.

Anthers are basifixed, dithecous with long filament, introrse and longitudinally dehiscent.

Gynoecium

Ovary superior, bicarpellary and syncarpous.

Ovary basically bilocular but tetralocular due to the formation of false septa.

Carpels are obliquely placed and ovules on swollen axile placenta. Style simple, long and filiform. Stigma two lobed.

Spinescent capsule opening by four apical valves with persistent calyx.

Seed

Endospermous.

ECONOMIC IMPORTANCE OF Solanaceae

1. Food plants

Tubers of Solanum tuberosum (potato) are used as common vegetable throughout the world.

Tender fruits of S. melongena (brinjal) and ripened fruits of Lycopersicon esculentum (tomato) are used as delicious vegetables.

2. Medicinal plants

Roots of Atropa belladona yield powerful alkaloid ‘atropine’. It is used for relieving muscular pain.

Leaves and flowers of Datura stramonium are the sources of drug ‘stramonium’ used to treat asthma and whooping cough.

Leaves, flowers, berries of Solanum trilobatum (thoodhuvalai) are used to treat cough.

Roots and leaves of Withania somnifera (Amukkara) are used to treat nervous disorder and are diuretic apart from useful tonic.

3. Tobacco

Leaves of Nicotiana tabacum (tobacco) contain alkaloids nicotine, nornicotine and anabasine.

Nicotine is considered to be the principal alkaloid in commercial tobaccos such as cigarette, bidi, pipes and hukkah as well as chewing and snuffing.

It is also used as sedative, antispasmodic and insecticide.

4. Ornamental plants

Cestrum diurnum (day jasmine), C. nocturnum (night jasmine) and Petunia hybrida (pink flower) are grown in gardens for their beautiful flowers.

Back to botany topic list

QUESTION For Solanaceae:

1. What is atropine?
2. Give the systematic position of Solanaceae.
3. Write the binomials of any three medicinally useful plants in Solanaceae.
4. Describe the gynoecium of members of Solanaceae.
5. Write the different types of inflorescence found in Solanaceae. Give examples for each.
6. Draw the floral diagram and write the floral formula of Datura metal.
7. Write any three binomials of food plants of Solanaceae.
8. Name the alkaloids found in tobacco.
9. Give an account of the economic importance of the family Solanaceae.
10. Describe Datura metal in botanical terms.
11. Write the general characteristic features of Solanaceae.

Click Here to get more information about Solanaceae

Other links 

TAXONOMY OF ANGIOSPERMS, TYPES OF CLASSIFICATION

---

BIOSYSTEMATICS NOMENCLATURE

---

BINOMIAL NOMENCLATURE, ICBN

---

HERBARIA AND ITS USES IMPORTANCE OF HERBARIUM

---

Bentham and Hooker’s classification of plants

---

Dicot Families – MALVACEAE

---

Botanical description of Hibiscus and Economical importance of Malvaceae

---

 

Euphorbiaceae and Ricinus communis and its Economic importance

---

Musaceae – Musa paradisiaca and its Economic Importance

Dicot Families – MALVACEAE  

Dicot Families – MALVACEAE

Back to botany topic list

DICOT FAMILIES – MALVACEAE – the cotton family

Systematic position
Class: Dicotyledonae
Sub-class: Polypetalae
Series: Thalamiflorae
Order: Malvales
Family: Malvaceae

General characters 

Distribution

This family includes about 82 genera and more than 1,500 species.

The plants are cosmopolitan in distribution, more abundant in tropical and subtropical regions.

In India, Malvaceae is represented by 22 genera and 125 species.

Habit

Plants may be annual herbs ( eg. Malva sylvestris) or perennial shrubs (eg. Hibiscus rosa-sinensis) or trees (eg. Thespesia populnea).

The members of this family have mucilagenous substance. Stellate hairs occur on their young parts.

Root

Tap root system.

Stem

Aerial, erect (eg. Malva sylvestris), branched, woody (eg. Thespesia populnea), decumbent as in Malva rotundifolia (Thirikalamalli) and usually covered with stellate hairs.

Leaf

Petiolate, simple, entire (eg. Thespesia populnea) or palmately lobed (eg. Gossypium arboreum), alternate, stipulate, margins usually toothed (eg. Hibiscus rosa-sinensis) and showing reticulate venation.

Inflorescence

Solitary, terminal (eg. Malvastrum coromendelia) or solitary, axillary (eg.Thespesia populnea) or terminal or axillary cyme.eg.Pavonia odorata (Peramutti).

Flower

Bracteate or ebracteate, bracteolate or ebracteolate, pedicellate, dichlamydeous, pentamerous, complete, actinomorphic, regular, bisexual and hypogynous.

Epicalyx

Bracteoles forming a whorl outer to calyx is called epicalyx. Bracteoles 3 in Malva sylvestris, 5 to 8 in Hibiscus rosa-sinensis, 10 to 12 in Pavonia odorata and absent in Abutilon indicum.

Calyx

Sepals 5, green, gamosepalous showing valvate
aestivation. Corolla
Petals 5, coloured, polypetalous but slightly fused at the base due to adhesion with staminal tube, regular and showing twisted aestivation.

Androecium

Numerous stamens, filaments are fused to form a staminal tube around the style and monadelphous.

The staminal tube is fused with the petals at their bases.

Anthers are monothecous, reniform, transversely attached to filaments and transversely dehiscent.

Gynoecium

Ovary superior, two to many carpels but usually 5 to 10 carpels and syncarpous.

Ovary with two to many locules. Pentacarpellary in Hibiscus rosa-sinensis, 10 in Althaea and 15 to 20 in Abutilon indicum.

Number of locules usually corresponds to number of carpels.

Each locule contains one to many ovules on axile placentation.

Style long, slender and passes through the staminal tube ending in two to many distinct round stigmas.

Fruit

Loculicidal capsule e.g. Abelmoschus esculentus or schizocarp as in Abutilon indicum and Sida cordifoliaI (Nilathuthi).

Seed

Endosperm is scanty, covered with hairs as in Gossypium barbadense.

Back to botany topic list

Explain the MALVACEAE General characters with detail?

Describe briefly General characters malvaceae ?

Mention the systematic position of Malvaceae.

Name any three fibre plants of Malvaceae.

Write any three binomials of food plants of Malvaceae.

List out characteristic features of members of Malvaceae.

For more details  Click Here

Other links 

TAXONOMY OF ANGIOSPERMS, TYPES OF CLASSIFICATION

---

BIOSYSTEMATICS NOMENCLATURE

---

BINOMIAL NOMENCLATURE, ICBN

---

HERBARIA AND ITS USES IMPORTANCE OF HERBARIUM

---

Bentham and Hooker’s classification of plants

---

Botanical description of Hibiscus and Economical importance of Malvaceae

---

Solanaceae – Datura metal and Economic importance

---

Euphorbiaceae and Ricinus communis and its Economic importance

---

Musaceae – Musa paradisiaca and its Economic Importance