Unit 2 — Structural Organisation in Plants and Animals  

Introduction:

The description of the diverse forms of life on earth was made only by observation – through naked eyes or later through magnifying lenses and microscopes. Hence, the descriptions made were mainly of gross structural features, both external and internal.
In the following chapters of this unit, the structural organisation of plants and animals on the structural basis of physiological (functions of living organs) and behavioural phenomena are described.

Concept box: Morphology is the branch of biology dealing with the study of the form, structure and specific structural features of organisms. Size, shape and structure of an organism are some of the morphological features. Anatomy is the branch of biology that focuses on the structure of living things like, body parts like, glands, muscles, organs, systems and so on

For convenience, the description of morphological and anatomical features is presented separately for plants and animals.

Story box: Katherine Esau born in Ukraine in 1898 discovered that the curly top virus spreads through a plant via the foodconducting or phloem tissue. The Anatomy of Seed Plants by Katherine Esau was published in 1960. It was referred to as Webster’s of plant biology.

Preview:

We shall discuss the features of flowering plants. In general, the portion of the plant above the ground constitutes the shoot system and the portion below the ground constitutes the root system.

The part of a plant that grows downward and holds the plant in place, absorbs water and minerals from the soil, and often stores food is the root. The root arises from the radicle of the embryo whereas, the shoot from the plumule. The two important types of roots are: Tap root and Fibrous root. The roots that arise from parts of the plant other than the radicle is called, an adventitious root. The roots help absorb water, store food, provide support and synthesize growth regulators in plants. We shall also discuss in brief, the various regions of the root, differentiated based on their functions.

In the section, we shall we will come across some special types of roots like, stilt roots and prop roots. Next, we shall study about the stem which is the ascending part of the axis bearing branches, leaves, flowers and fruits. Its functions and modifications shall then be discussed.

We will then take up the study of leaves. A leaf is a lateral, generally flattened structure borne on the stem. Its functions, types of venation on it and its parts shall be discussed. We shall also study the different types of leaves based on the incisions formed on them.

Phyllotaxy and its types shall then be dealt with. Phyllotaxy is the pattern of arrangement of leaves on the stem or branch. As we discuss for root and stem, the modifications in leaves shall also be discussed briefly.

A flower is a modified shoot formed by differentiation of shoot apical meristem into floral meristem and the arrangement of flowers on the floral axis is termed as inflorescence. There are 4 major whorls that the flower is made of. They are: calyx (individual unit – sepal), corolla (individual unit – petal), androecium (individual unit stamen) and gynoecium (individual unit – carpel or pistil). We shall then classify flowers based on various criteria.

In the next section, we will talk about fruits that are mature or ripened ovary, developed after fertilisation. The ovules after fertilisation develop into seeds.

Next, we shall see how the various parts of a flower can be described through a diagrammatic representation called, floral diagram and a succinct formula called, floral formula.

Finally, important features such as habitat, classification, vegetative characters, floral characters and economic importance for some important families of flowering plants shall be studied.

5.0 Introduction:

Angiosperms show such a large diversity in external structure or morphology, they are all characterised by presence of roots, stems, leaves, flowers and fruits.

Thus, when we pull out any weed you will see that all of them have roots, stems and leaves. They may be bearing flowers and fruits as well.

The underground part of the flowering plant is what constitutes the root system while the portion above the ground forms the shoot system (Figure 5.1).

5.1 The Root

Definition box: Root: The part of a plant that grows downward and anchors the plant in place, absorbs water and minerals from the soil, and often stores food is the root.

Concept box: The embryo enclosed in the seed protrudes out of the seed as it grows and differentiates to form two structures namely, radicle and plumule. Radicle forms the future root and is protected by a sheath called, coleorhiza. Plumule forms the future shoot and is protected by a sheath called as coleoptile.

Dicotyledonous plants:

Concept box: Lateral growth: Growth towards the side-ways direction.

In most Dicotyledonous plants, the direct elongation of the radicle leads to the formation of primary root which grows inside the soil.
The primary root branches into lateral roots referred to as secondary roots, tertiary roots and so on.
The primary roots and its branches constitute the tap root system.
Example for a tap root: root of mustard plant (Figure 5.2a).

Monocotyledonous plants: In monocotyledonous plants, the primary root is short lived and is then replaced by a large number of roots.

These roots originate from the base of the stem and constitute the fibrous root system as seen in the wheat plant (Figure 5.2b). They arise from repeated branching of the radical.

In some plants, like grass, Monstera and the banyan tree, roots arise from parts of the plant other than the radicle and are called adventitious roots (Figure 5.2c).

Functions of roots:

5.1.1 Regions of the Root

The root is covered at the apex by a thimble-like structure called the root cap (Figure 5.3 above). It protects the tender apex of the root as it makes its way through the soil.
A few millimetres above the root cap is the region of meristematic activity. The cells of this region are very small, thin-walled and with dense protoplasm. These cells divide repeatedly.
The cells situated at the proximity of the meristematic zone, undergo rapid elongation and enlargement and are responsible for the growth of the root, lengthwise. Hence, this region is called the region of elongation.
The cells of the elongation zone gradually differentiate and mature as they grow. Hence, this zone proximal to region of elongation is called the region of maturation.
From this region some of the epidermal cells form very fine and delicate, thread-like structures called root hair. The root hair absorbs water and minerals from the soil.

5.1.2 Modifications of Root

Roots in some plants change their shape and structure and become modified to perform specific functions other than absorption and conduction of water and minerals.
They are modified for support, storage of food or for respiration as illustrated in the following examples:
Tap roots of carrot, turnip and adventitious roots of sweet potato get swollen and store food.

The hanging structures that support a banyan tree are called prop roots.

Similarly, the stems of maize and sugarcane have supporting roots which emerge from the lower nodes of the stem. These are called stilt roots.

In some plants such as Rhizophora growing in swampy areas, many roots come out of the ground and grow vertically upwards. Such roots are called pneumatophores. The pneumatophores help in drawing oxygen from air for respiration.

Questions from section 5.1:

1. List the characteristics of monocotyledonous and dicotyledonous plants.
2. Explain the functions of roots.
3. Explain with a diagram, the regions in a root. 4. Illustrate with examples, modifications in roots.

5.2 The Stem

The stem is the ascending part of the axis bearing branches, leaves, flowers and fruits.

Development and structure of the stem:

The stem develops from the plumule of the embryo of a germinating seed.
The stem bears nodes and internodes.
The regions of the stem where leaves are born are called nodes while internodes are the portions between two nodes.
The stem bears buds, which may be terminal or axillary.
Stem is generally green when young and later often become woody and dark brown.
The main function of the stem is to support branches, leaves, flowers and fruits.
The stem also helps conduct water, minerals and in photosynthesis.
Some stems perform the function of storage of food, support, protection and of vegetative propagation.

5.2.1 Modifications of Stem

Concept box: Perennation is the ability of plants to survive under unfavourable conditions such as drought or winter.

The stem is modified to perform different functions as illustrated by the following examples:

a) Underground stems of potato, ginger, turmeric, zaminkand, Colocasia are modified to store food in them. They also act as organs of perennation during unfavourable conditions.

b) Stem tendrils which develop from axillary buds, are slender and spirally coiled and help plants to climb such as in gourds (cucumber, pumpkins, watermelon) and grapevines.

c) Axillary buds of stems may also get modified into woody, straight and pointed thorns. Thorns are found in many plants such as Citrus, Bougainvillea. They protect plants from browsing (or grazing) animals.

d) Fleshy structures: Some plants of arid regions modify their stems into flattened (Opuntia), or fleshy cylindrical (Euphorbia) structures. They contain chlorophyll and are specialized to carry out photosynthesis.

e) Underground stems of some plants such as grass and strawberry are used to spread into new niches and when older parts die new plants are formed.

f) Lateral branches: In plants like mint and jasmine, a slender lateral branch arises from the base of the axil of the stem. This lateral branch grows aerially for some time and then arches downwards to touch the ground.

Sometimes, the lateral branch develops short internodes to house a rosette of leaves and a tuft of roots with it. This type of lateral branching is found in aquatic plants like Pistia and Eichhornia.

In banana, pineapple and Chrysanthemum, the lateral branches originate from the basal and underground portion of the main stem but, grow horizontally beneath the soil and then come out obliquely upward bearing leafy shoots.

Questions from section 5.2:

1. What is a stem? Explain different parts of the stem and its functions.
2. Explain with examples, the modifications in a stem.

5.3 The Leaf

Concept box: Acropetal order: The developing or opening of leaves or flowers in succession from base to apex. Basipetal order: The developing or opening of leaves or flowers; developing or opening in succession from apex to base.

The leaf is a lateral, generally flattened structure borne on the stem.
A leaf develops at the node and bears a bud in its axil. The axillary bud later develops into a branch.
Leaves originate from shoot apical meristems (cells located at the tip of the shoot) and are arranged in an acropetal order.
They are the most important vegetative organs for photosynthesis.
A typical leaf consists of three main parts: leaf base, petiole and lamina (Figure 5.9).

The leaf is attached to the stem by the leaf base and sometimes bears two lateral small leaf-like structures called, stipules (shown in figure 5.9).
In monocotyledons, the leaf base expands into a sheath covering the stem partially or wholly.
In some leguminous plants, the leafbase may become swollen, which is called the pulvinus.
The petiole helps in holding the leaf blade to light. Long thin flexible petioles allow leaf blades to flutter in wind, thereby cooling the leaf and bringing fresh air to leaf surface.
The lamina or the leaf blade is the green expanded part of the leaf with veins and veinlets. There is, usually, a middle prominent vein, which is known as the midrib. Veins provide rigidity to the leaf blade and act as channels of transport for water, minerals and food materials.
The shape, margin, apex, surface and extent of incision of lamina vary in different leaves.

5.3.2 Types of Leaves

a) Simple leaf: A leaf is said to be simple, when its lamina is entire or when there are incisions in it but the incisions are such that they do not touch the midrib. A bud is present in the axil of petiole and at the axil of leaflets in a simple leaf.

b) Compound leaf: When the incisions of the lamina reach up to the midrib breaking it into a number of leaflets, the leaf is called compound. A bud is present in the axil of petiole in compound leaves, but not in the axil of leaflets of the compound leaf.

The compound leaves may be of two types:

a) Pinnately Compound leaf: In a pinnately compound leaf, a number of leaflets are present on a common axis called, rachis, which represents the midrib of the leaf as in neem:

b) Palmately Compound leaves: In palmately compound leaves, the leaflets are attached at a common point, that is, at the tip of petiole, as in silk cotton.

5.3.3 Phyllotaxy

Phyllotaxy is the pattern of arrangement of leaves on the stem or branch.
Phyllotaxy is of three types: alternate, opposite and whorled.

Alternate phyllotaxy: In alternate type of phyllotaxy, one leaf arises at each alternate node, as in China rose, mustard and sun flower plants.

Opposite phyllotaxy: In opposite type, a pair of leaves arise at each node and lie opposite to each other as in Calotropis and guava plants.

Whorled phyllotaxy: If more than two leaves arise at a node and form a whorl, it is called whorled, as in Alstonia.

5.3.4 Modifications of Leaves

Leaves are modified to perform functions other than photosynthesis like:

a) Tendrils: They are used for climbing as in peas (Figure 5.12a).

b) Spines: Leaves are modified into spines for defence as in cacti (Figure 5.12b).

c) Storage: The fleshy leaves of onion and garlic store food (Figure 5.12c).

d) In some plants such as Australian acacia, the leaves are small and short-lived. The petioles in these plants expand, become green and synthesise food.

e) Leaves of certain insectivorous plants such as pitcher plant, venus-fly trap are also modified leaves.

Questions from section 5.3:

1. What is a leaf? Explain its parts with a diagram.
2. What are the functions of a leaf?
3. Draw and name the two types of venations observed in leaves.
4. Classify and explain the different types of leaves.
5. What is phyllotaxy? Explain the types.

5.4 The Inflorescence

A flower is a modified shoot formed by differentiation of shoot apical meristem into floral meristem.
During the formation of a flower, the internodes do not elongate and the axis (of the stem) gets condensed.
The apex of the shoot produces different kinds of floral appendages (or floral parts) laterally at successive nodes instead of producing leaves at these nodes.
When a shoot tip transforms into a flower, it forms a solitary flower.
The arrangement of flowers on the floral axis is termed as inflorescence.
Depending on whether the apex gets converted into a flower directly or continues to grow, two major types of inflorescences are defined racemose and cymose;
In racemose type of inflorescences the main axis continues to grow, the flowers are borne laterally in an acropetal succession (Figure 5.13).

In cymose type of inflorescence the main axis terminates in a flower, hence is limited in growth. The flowers are borne in a basipetal order (Figure 5.14).

5.5 The Flower

In angiosperms, the flower is the reproductive unit meant for sexual reproduction.

A typical flower has four different kinds of whorls arranged successively on the swollen end of the stalk or pedicel, called thalamus or receptacle.

The 4 main whorls are: calyx, corolla, androecium and gynoecium. Calyx and corolla are accessory organs, while androecium and gynoecium are reproductive organs.
The calyx is comprised of individual units of sepals and the coroalla is comprised of individual units of petals. Similarly, the individual units of androecium are the stamens and that of gynoecium are the carpels or pistils.
In some flowers like lily, the calyx and corolla are not distinct (or are fused into one) and are called as perianth. The individual units that make up the perianth are called, tepals.
When a flower has both androecium and gynoecium, it is bisexual.
A flower having either the androecium or the gynoecium but not both in the same flower, is said to be unisexual.
Some flowers have bracts. A bract is a reduced leaf found at the base of the pedicel.

Symmetry: The symmetry in flowers can be categorized into: Actinomorphic (radial symmetry), Zygomorphic (bilateral symmetry) and Asymmetric.

a) Actinomorphic: When a flower can be divided into two equal radial halves in any radial plane passing through the centre, it is said to be actinomorphic, for example, mustard, datura, chilli.

b) Zygomorphic: When a flower can be divided into two similar halves only in one particular vertical plane, it is zygomorphic, for example, pea, gulmohur, bean, Cassia.

c) Asymmetric: A flower is asymmetric (irregular) if it cannot be divided into two similar halves by any vertical plane passing through the centre, as in canna.

Types of flowers:
a) Depending on the number of individual units: A flower may be trimerous, tetramerous or pentamerous when the floral appendages are in multiple of 3, 4 or 5, respectively. For example, a flower having 3 or 6 or 9 petals, stamens, pistils and sepals is said to be trimerous.

b) Depending on the absence or presence of bracts: Flowers with bracts are called bracteate and those without bracts, ebracteate.

c) Based on the position of calyx, corolla and androecium with respect to the position of ovary on the thalamus, the flowers are described as, hypogynous, perigynous and epigynous (Figure 5.16);

In the hypogynous flower, the gynoecium occupies the highest position while the other parts are situated below it. The ovary in such flowers is said to be superior, for example, mustard, china rose and brinjal.

In the perigynous flower, the gynoecium is situated in the centre and other parts of the flower are located on the rim of the thalamus almost at the same level. The ovary here is said to be half inferior, for example, plum, rose, peach.

In epigynous flowers, the margin of thalamus grows upwards enclosing the ovary completely and getting fused with it, the other parts of flower arise above the ovary. Hence, the ovary is said to be inferior as in flowers of guava and cucumber, and the ray florets of sunflower.

5.5.1 Parts of a Flower

As discussed in the previous section, each flower normally has four floral whorls, viz., calyx, corolla, androecium and gynoecium (Figure 5.17). We shall now study about these in detail.

5.5.1.1 Calyx

The calyx is the outermost whorl of the flower and the members are called sepals.
Generally, sepals are green, leaf like and protect the flower in the bud stage.
The calyx can either be gamosepalous (sepals united) or polysepalous (sepals free).

5.5.1.2 Corolla

Corolla is composed of petals.
Petals are usually brightly coloured to attract insects for pollination. However, the shape and colour of corolla vary greatly in plants.
Petals constituting the corolla may be united in which case it is called, gamopetalous. If the petals are separate or free, the condition is called, polypetalous.
Corolla may be tubular, bellshaped, funnel-shaped or wheel-shaped.
Aestivation: The mode of arrangement of sepals or petals in floral bud with respect to the other members of the same whorl is known as aestivation.

The 4 main types of aestivation are:

a) Valvate: When sepals or petals in a whorl just touch one another at the margin, without overlapping, as in Calotropis, it is said to be valvate.

b) Twisted: If one margin of the appendage overlaps that of the next one and so on as in china rose, lady s finger and cotton, it is called twisted.

c) Imbricate: If the margins of sepals or petals overlap one another but not in any particular direction as in Cassia and gulmohur, the aestivation is called imbricate.

d) Vexillary: In pea and bean flowers, there are five petals, the largest (standard) overlaps the two lateral petals (wings) which in turn overlap the two smallest anterior petals (keel); this type of aestivation is known as vexillary or papilionaceous.

5.5.1.3 Androecium

Concept box: Sterile: The condition wherein, the reproductive organ in an organism does not have the ability to reproduce.

Androecium is composed of stamens. Each of the stamens represents a male reproductive organ.
The stamen consists of a stalk or a filament and an anther.
Each anther is usually bilobed with each lobe in turn containing two chambers called, the pollen-sacs.
The pollen grains are produced in pollen-sacs.
A sterile stamen is called staminode.

Types of stamens:

Stamens of flower may be united with other members such as petals or among themselves based on which they could be:

a) Epipetalous: When stamens are attached to the petals, they are epipetalous as in brinjal.

b) Epiphyllous: When attached to the perianth, they are epiphyllous as in the flowers of lily.

Based on whether the stamens are united or free:

a) Polyandrous: When the stamens in a flower are free or may be united in varying degrees, they are called, polyandrous.

b) Monoadelphous, diadelphous and polyadelphous: When the stamens are united into one bunch or one bundle as in china rose, they are called Monoadelphous; similarly, when united to form two bundles, diadelphous as in pea, and when united into more than two bundles, polyadelphous as in citrus.

Note box: The stamens also vary in the length of filaments within a flower, as in Salvia and mustard.

5.5.1.4 Gynoecium

Gynoecium is the female reproductive part of the flower and is made up of one or more carpels.
A carpel consists of three parts namely stigma, style and ovary.
Ovary is the enlarged basal part.
The style is the elongated tube that arises from the ovary. The style connects the ovary to the stigma.
The stigma is usually at the tip of the style and is the receptive surface for pollen grains.
Each ovary bears one or more ovules attached to a flattened, cushion-like placenta.

Types of carpels:

a) Apocarpous: When more than one carpel is present, they may be free (as in lotus and rose) and are called apocarpous.

b) Syncarpous: When carpels are fused, they are called, syncarpous as in mustard and tomato.

After fertilisation, the ovules develop into seeds and the ovary matures into a fruit.

Placentation: The mode of arrangement of ovules within the ovary is known as placentation.

Placentation is of different types namely, marginal, axile, parietal, basal, central and free central (Figure 5.19):

a) Marginal Placentation: In marginal placentation the placenta forms a ridge along the ventral suture of the ovary and the ovules are borne on this ridge forming two rows, as in pea.

b) Axile Placentation: When the placenta is axial and the ovules are attached to it in a multilocular ovary, the placentaion is said to be axile, as in China rose, tomato and lemon.

c) Parietal Placentation: In parietal placentation, the ovules develop on the inner wall of the ovary or on peripheral part. Ovary is one-chambered but it becomes two-chambered due to the formation of the false septum, for example, in mustard and Argemone.

d) Free central: When the ovules are borne on central axis and septa are absent, as in Dianthus and Primrose the placentation is called, free central.

e) Basal placentation: In basal placentation, the placenta develops at the base of the ovary and a single ovule is attached to it, as in sunflower and marigold.

Question from sections 5.4 and 5.5:

1. Describe the terms:

1. Flower
2. Solitary flower
3. inflorescence

2. Explain the types of inflorescence with diagrams.

3. What are the 4 whorls found in a flower? Specify the individual units they are comprised of.

4. What are a unisexual flower and a bisexual flower?

5. What is a bract?

6. Explain the types of symmetry in flowers.

7. Explain the types of flowers based on the following features:
a) number of individual units in their whorl
b) absence or presence of bract
c) position of calyx, corolla and androecium with respect to ovary on thalamus

8. Write a note on the following parts of a slower:

1. Calyx
2. Corolla
3. Androecium

9. What is aestivation? Explain its types.

10. Describe the types of stamens and carpels.

11. What is placentation? Explain the types of placentation.

5.6 The Fruit

The fruit is a mature or ripened ovary, developed after fertilisation.
Parthenocarpic fruit: If a fruit is formed without fertilisation of the ovary, it is called a parthenocarpic fruit.

Parts of a fruit:

Generally, the fruit consists of a wall or pericarp and seeds.

The pericarp is dry or fleshy. When pericarp is thick and fleshy, it is differentiated into the outer epicarp, the middle mesocarp and the inner endocarp.

The fruits that develop from monocarpellary (single carpel) superior ovaries and are one seeded, are called as drupes. For example, in mango and coconut (Figure 5.20).

In mango the pericarp is well differentiated into an outer thin epicarp, a middle fleshy edible mesocarp and an inner stony hard endocarp. In coconut which is also a drupe, the mesocarp is fibrous.

5.7 The Seed

The ovules after fertilisation develop into seeds.
A seed is made up of a seed coat and an embryo.
The embryo is made up of a radicle, an embryonal axis and one cotyledon (as in wheat and maize) or two cotyledons (as in gram and pea).

5.7.1 Structure of a Dicotyledonous Seed

The outermost covering of a seed is the seed coat.
The seed coat has two layers, the outer testa and the inner tegmen.
The hilum is a scar of the developing seed attached to the fruit left on the seed coat.
Above the hilum is a small pore called the micropyle.
Within the seed coat is the embryo, consisting of an embryonal axis and two cotyledons.
The cotyledons are often fleshy and full of reserve food materials.
At the two ends of the embryonal axis are present the radicle and the plumule (Figure 5.18).

In some seeds such as castor, the endosperm that forms as a result of double fertilisation is a food storing tissue. In plants such as bean, gram and pea, the endosperm is not present once the seeds mature and such seeds are called non-endospermous.

5.7.2 Structure of Monocotyledonous Seed

Generally, the monocotyledonous seeds are endospermic but some as in orchids are non-endospermic.
In the seeds of cereals such as, maize the seed coat is membranous and fused with the fruit wall.
In monocotyledonous seeds, the endosperm is bulky and stores food.
The outer covering of endosperm separates the embryo by a proteinous layer called aleurone layer.
The embryo is small and situated in a groove at one end of the endosperm. The embryo consists of one large and shield shaped cotyledon known as scutellum and a short axis with a plumule and a radicle.
The plumule and radicle are enclosed in sheaths which are called coleoptile and coleorhiza respectively (Figure 5.22).

5.8 Semi-Technical Description of a Typical Flowering Plant

Rules followed in presenting a semi-technical description of a flowering plant:

Various morphological features are used to describe a flowering plant. The description has to be brief, simple, in a scientific language and presented in a proper sequence.
The plant is described beginning with its habit, followed by its vegetative characters roots, stem and leaves and then; floral characters type of inflorescence and flower parts.
After describing various parts of plant, a floral diagram and a floral formula are presented.

The floral diagram:

The position of the mother axis with respect to the flower is represented by a dot on the top of the floral diagram.

Calyx, corolla, androecium and gynoecium are drawn in successive whorls, calyx being the outermost and the gynoecium being in the centre.

A floral diagram provides information about the number of parts of a flower, their arrangement and the relation they have with one another.

The floral formula:

The floral formula is represented by a set of symbols:

Br stands for bracteates,
K stands for calyx,
C for corolla,
P for perianth,
A for androecium and G for Gynoecium;

Fusion is indicated by enclosing the figure within bracket and adhesion by a line drawn above the symbols of the floral parts

Floral formula also shows cohesion and adhesion within parts of whorls and between whorls.

The floral diagram and floral formula for mustard plant (Family: Brassicaceae) is represented in Figure 5.23.

Questions from sections 5.6 to 5.8:

1. What is a fruit?
2. What is a parthenocarpic fruit?
3. Explain the parts of a fruit.
4. What is a seed? Explain its constituents.
5. Explain with diagrams, the structures of dicot and monocot seeds.
6. Write a note on floral diagram.
7. Explain the various symbols used to write the floral formula.

5.9 Description of Some Important Families

5.9.1 Fabaceae

Concept box: Stipule: A small leaf-like appendage to a leaf, typically borne in pairs at the base of the leaf stalk. A leaf that possesses a stipule is said to be stipulate and that which does not is called, exstipulate.

General info: The Fabaceae family was earlier called Papilionoideae.

Classification: Fabaceae is a subfamily of the family, Leguminosae.

Habitat: It is distributed all over the world.

Vegetative Characters:

• They exist as trees, shrubs and herbs.
• They have roots with root nodules.
• Stem is erect or modified into a climber.

Leaves: alternate, pinnately compound or simple; with leaf base: pulvinate (swollen leaf base); stipulate; venation: reticulate (the condition in which a network of veins attached to the midrib).

Floral characters:

Inflorescence: racemose

Flower: bisexual, zygomorphic

Calyx: sepals-five, gamosepalous; valvate or imbricate aestivation

Corolla: petals five, polypetalous, papilionaceous, consisting of a posterior standard two lateral wings, two anterior wings forming a keel (enclosing stamens and pistil), vexillary aestivation

Androecium: ten, diadelphous, anther-dithecous

Gynoecium: ovary superior, mono carpellary, unilocular with many ovules, style single

Fruit: legume; seed: One or more, non-endospermic

Floral Formula:

Economic importance
Many plants belonging to the family are sources of pulses (gram, arhar, sem, moong, soyabean; edible oil (soyabean, groundnut);

dyes (Indigofera);

fibres (sunhemp);

fodder (Sesbania, Trifolium),

ornamentals (lupin, sweet pea) and,

medicine (muliathi).

5.9.2 Solanaceae

General info: It is a large family, commonly called as the potato family.

Habitat: It is widely distributed in tropics, subtropics and even temperate zones (Figure 5.25).

Vegetative Characters

The plants of the Solanaceae exist as herbs, shrubs and rarely small trees

Stem: herbaceous rarely woody, aerial; erect, cylindrical, branched, solid or hollow, hairy or glabrous, underground stem in potato (Solanum tuberosum)

Leaves: alternate, simple, rarely pinnately compound, exstipulate; venation: reticulate

Floral Characters

Inflorescence: Solitary, axillary or cymose as in Solanum
Flower: bisexual, actinomorphic
Calyx: sepals five, united, persistent, valvate aestivation
Corolla: petals five, united; valvate aestivation
Androecium: stamens five, epipetalous
Gynoecium: bicarpellary, syncarpous; ovary superior, bilocular, placenta swollen with many ovules
Fruits: berry or capsule
Seeds: many, endospermous

Floral Formula:

Economic Importance

Many plants belonging to this family are source of:

food (tomato, brinjal, potato)

spice (chilli);

medicine (belladonna, ashwagandha);

fumigatory (tobacco) and,

ornamentals (petunia).

5.9.3 Liliaceae

General info: Liliaceae is generally referred to as the Lily family. It is a characteristic representative of monocotyledonous plants.

Habitat: It is distributed worldwide.

Vegetative characters:

They exist as perennial herbs with underground bulbs or corms (bulb or tuber) or rhizomes

Leaves: mostly basal, alternate, linear, exstipulate with parallel venation

Floral characters

Inflorescence: solitary or cymose; often umbellate clusters

Flower: bisexual; actinomorphic

Perianth: tepal-six (3+3), often united into tube; valvate aestivation

Androecium: stamen-six, 3+3, epitepalous

Gynoecium: tricarpellary, syncarpous, ovary superior, trilocular with many ovules; axile placentation

Fruit: capsule, rarely berry

Seed: endospermous

Floral Formula:

Economic Importance:

Many plants belonging to this family are:

good ornamentals (tulip, Gloriosa),

source of medicine (Aloe),

vegetables (Asparagus) and,

colchicine (Colchicum autumnale).

Question from section 5.9:

Describe (with regard to habitat, classification, vegetative characters, floral characters and economic importance) the following families:
a) Fabaceae
b) Solanaceae
c) Liliaceae