Plant Morphology

The Root

The root is the underground part of the plant body. It develops from the radicle of the embryo. The root is typically non-green (achlorophyllous) and lacks nodes and internodes.

Types of Root Systems

Tap Root System: Develops from the radicle. The primary root grows downwards and produces lateral roots (secondary, tertiary roots, etc.). The primary root is the main root.
Example: Found in dicotyledonous plants (e.g., mustard, gram, pea).
Fibrous Root System: The primary root is short-lived and is replaced by a large number of roots arising from the base of the stem. These roots form a cluster of fibrous roots.
Example: Found in monocotyledonous plants (e.g., wheat, rice, maize).
Adventitious Root System: Roots arise from parts of the plant other than the radicle, such as the stem, branches, or leaves.
Example: Found in grass, Monstera, banyan tree.

Diagram showing Tap, Fibrous, and Adventitious root systems

*(Image shows diagrams illustrating the structure of tap root system, fibrous root system, and adventitious roots)*

Functions of Root

Absorption of water and minerals from the soil.
Anchorage of the plant body to the soil.
Storage of reserve food material.
Synthesis of plant growth regulators.

Regions of the Root

The apex of the root is covered by a thimble-like structure called the root cap, which protects the tender apex as it grows through the soil. Above the root cap, there are three distinct regions:

Region of Meristematic Activity: Located a few millimetres above the root cap. Cells in this region are small, thin-walled, and actively dividing (meristematic).
Region of Elongation: Located just above the meristematic region. Cells in this region undergo rapid elongation and enlargement, which is responsible for the increase in length of the root.
Region of Maturation: Located above the region of elongation. Cells in this region differentiate and mature. Some epidermal cells in this region form slender, unicellular extensions called root hairs.
Function of root hairs: Greatly increase the surface area for absorption of water and minerals.

Diagram showing the different regions of a root tip (root cap, meristematic, elongation, maturation with root hairs)

*(Image shows a longitudinal section of a root tip highlighting the root cap, meristematic region, elongation region, and maturation region with root hairs)*

Modifications of Root

Roots are modified in various ways to perform functions other than absorption and anchorage.

Modifications for Storage

The roots become swollen and fleshy due to the storage of food.

Tap roots: Become fleshy and swollen. Examples:
- Conical (carrot)
- Fusiform (radish)
- Napiform (turnip, beetroot)
Adventitious roots: Become fleshy and swollen.
- Tuberous root (sweet potato) - single, large, irregular root.
- Fasciculated tuberous roots (Asparagus, Dahlia) - cluster of tuberous roots from the base of the stem.

Diagrams showing different types of fleshy storage roots (carrot, radish, turnip, sweet potato)

*(Image shows illustrations of modified tap roots (carrot, radish, turnip) and modified adventitious roots (sweet potato))*

Modifications for Support

Prop roots: Hanging structures that grow from the branches down to the soil, providing support to the spreading branches.
Example: Banyan tree ($Ficus \: benghalensis$).
Stilt roots: Roots growing obliquely from the lower nodes of the stem and entering the soil, providing support.
Example: Maize, Sugarcane.

Diagrams showing prop roots of banyan and stilt roots of maize/sugarcane

*(Image shows illustrations of prop roots from banyan branches and stilt roots from lower nodes of a stem)*

Modifications for Respiration

Pneumatophores: Vertically upward growing roots that emerge from the soil in some plants growing in swampy areas (like mangroves). They have pores (lenticels) to facilitate the exchange of gases for respiration.
Example: Rhizophora.

Diagram showing pneumatophores emerging from soil around a mangrove plant

*(Image shows a plant in swampy area with upward growing root-like structures emerging from the mud)*

Other Modifications

Climbing roots: Help the plant to climb walls or trees. Example: Money plant ($Epipremnum \: aureum$), Betel.
Epiphytic roots: Hanging roots of epiphytic plants (growing on other plants for support). They absorb moisture from the atmosphere with the help of a spongy tissue called velamen. Example: Vanda (an orchid).
Parasitic roots (Haustoria): Roots that penetrate the host tissue to absorb nutrients. Example: Cuscuta (Doder).
Storage roots: Already covered under storage (e.g., Sweet potato is adventitious).

The Stem

The stem is the ascending part of the plant axis, developing from the plumule of the embryo. It bears branches, leaves, flowers, and fruits. The stem is characterised by the presence of nodes and internodes.

A node is the point on the stem where leaves are borne. Internodes are the portions of the stem between two successive nodes.

The stem bears buds, which may be terminal (apical) or axillary. Axillary buds are present in the axil of leaves (the angle between the leaf and the stem).

Young stems are usually green and capable of photosynthesis, while mature stems often become woody and dark brown.

Functions of Stem

Provides structure and support to the plant, holding up branches, leaves, flowers, and fruits.
Conducts water and minerals from the roots to the leaves (via xylem).
Conducts food (sugars) from the leaves to other parts of the plant (via phloem).
May perform storage of food (e.g., potato, ginger).
May be involved in vegetative propagation (e.g., rose, sugarcane).
May perform photosynthesis (e.g., in modified stems like phylloclades).
May provide protection (e.g., thorns).

Modifications of Stem

Stems are modified to perform various functions like storage, support, protection, vegetative propagation, and perennation (survival during unfavourable conditions).

Underground Stem Modifications (for Storage and Perennation)

These stems remain underground and store food. They also help in vegetative propagation and survival.

Rhizome: Horizontal, underground stem with nodes, internodes, scale leaves, and buds. Bears adventitious roots on the lower side.
Example: Ginger, Turmeric.
Corm: Short, vertical, swollen underground stem with nodes, internodes, scale leaves, and buds. Bears adventitious roots at the base.
Example: Zamikand (Amorphophallus), Colocasia (Arbi).
Tuber: Swollen tip of an underground branch. No definite shape. Has 'eyes' which are nodes bearing axillary buds.
Example: Potato.
Bulb: Condensed underground stem (disc-like) with fleshy scale leaves storing food. Bears terminal bud (shoot) and adventitious roots at the base.
Example: Onion, Garlic.

Diagrams showing underground stem modifications: Rhizome (Ginger), Corm (Colocasia), Tuber (Potato), Bulb (Onion)

*(Image shows illustrations of a ginger rhizome, a colocasia corm, a potato tuber with eyes, and an onion bulb)*

Sub-aerial Stem Modifications (for Vegetative Propagation)

These stems are partly above and partly below the ground, helping in vegetative spread.

Runner: Slender, prostrate branch arising from the base of the stem. It runs along the ground and produces roots and new shoots at nodes.
Example: Grass (like Cynodon), Strawberry.
Stolon: A slender lateral branch that arises from the base of the stem and grows upwards for some distance, then arches downwards to touch the ground, where it gives rise to a new plant.
Example: Mint, Jasmine.
Offset: A short, thick lateral branch arising from the base of the stem. It grows horizontally for a short distance and then produces a rosette of leaves and a tuft of roots at its apex. Found in aquatic plants.
Example: Pistia, Eichhornia (Water Hyacinth).
Sucker: A lateral branch arising from the basal, underground part of the stem. It grows horizontally underground for some distance and then emerges obliquely upwards to form a new shoot.
Example: Banana, Pineapple, Chrysanthemum.

*(Image shows illustrations of plants with runners, stolons, offsets (in water), and suckers)*

Aerial Stem Modifications

Stem Tendrils: Slender, spirally coiled structures that help the plant to climb. They develop from axillary buds.
Example: Cucumber, Pumpkins, Watermelon, Grapevine.
Thorns: Hard, pointed, woody structures developed from axillary buds. Provide protection from browsing animals.
Example: Citrus, Bougainvillea.
Phylloclade: Flattened or cylindrical succulent stem modifications that perform photosynthesis. Found in arid regions to reduce water loss.
Example: Opuntia (flattened), Euphorbia (cylindrical). Leaves are often reduced to spines.
Cladode: Similar to phylloclade but consists of only one or two internodes (e.g., Asparagus).

*(Image shows illustrations of a stem tendril, a thorn, and a photosynthetic flattened stem)*

The Leaf

The leaf is a lateral, flattened structure borne on the stem, typically green and responsible for photosynthesis. It develops from the shoot apical meristem and is arranged in an acropetal order (older leaves at the base, younger towards the apex). Leaves are borne at the nodes.

Parts of a Typical Leaf

A typical leaf consists of three main parts:

Leaf base: The part of the leaf attached to the stem.
- In some plants, the leaf base may be swollen, called the pulvinus (e.g., leguminous plants), which helps in sleep movements.
- In some monocots (e.g., grasses), the leaf base expands into a sheathing leaf base, covering the stem partially or wholly.
- Leaves may bear two lateral small leaf-like structures called stipules at the leaf base.
Petiole: The stalk of the leaf. It connects the lamina with the stem. Petiolate leaves have a petiole, sessile leaves do not.
Function: Holds the lamina to the light, allows fluttering of lamina which helps in cooling and uniform distribution of air.
Lamina (Leaf blade): The green, flattened part of the leaf where photosynthesis takes place. It contains veins and veinlets. The margin, apex, and surface of the lamina can vary in different plants.

Diagram showing parts of a typical leaf: leaf base, petiole, lamina, stipules

*(Image shows a simple leaf attached to a stem, highlighting the leaf base, petiole, lamina, and stipules)*

Venation

The arrangement of veins and veinlets in the lamina of a leaf is called venation.

Veins provide rigidity to the leaf blade, act as channels for transport of water, minerals, and food.

Types of venation:

Reticulate Venation: The veinlets form a network.
Example: Found in most dicotyledonous plants (e.g., Pea, Mustard, Mango).
Parallel Venation: The veins run parallel to each other within the lamina. Veinlets do not form a network.
Example: Found in most monocotyledonous plants (e.g., Grass, Wheat, Maize, Banana).

Diagrams showing reticulate and parallel venation in leaves

*(Image shows illustrations of a leaf with reticulate venation and a leaf with parallel venation)*

Types of Leaves

Leaves are classified into two main types:

Simple Leaf: A leaf is simple when its lamina is entire or when incised (cut) the incisions do not touch the midrib. A simple leaf has a single lamina attached to the stem by a petiole.
Compound Leaf: A leaf is compound when the incisions of the lamina reach the midrib or the petiole, breaking the lamina into a number of leaflets. A compound leaf consists of multiple leaflets attached to a common axis. An axillary bud is present in the axil of the petiole, but not in the axil of the leaflets.

Compound leaves are further classified based on how the leaflets are arranged:

Pinnately Compound Leaf: A common axis, the rachis, represents the midrib of the leaf. Leaflets are attached directly on the rachis in a pinnate manner.
Example: Neem ($Azadirachta \: indica$).
Palmately Compound Leaf: The leaflets are attached at a common point at the tip of the petiole, like the fingers on the palm of a hand.
Example: Silk Cotton ($Ceiba \: pentandra$).

Diagrams showing Simple leaf, Pinnately compound leaf (Neem), and Palmately compound leaf (Silk Cotton)

*(Image shows illustrations of a simple leaf, a pinnately compound leaf with leaflets on a rachis, and a palmately compound leaf with leaflets radiating from petiole tip)*

Phyllotaxy

Phyllotaxy is the pattern of arrangement of leaves on the stem or branch. This arrangement is specific for each plant species and is designed to provide optimal exposure of leaves to sunlight for photosynthesis.

Common types of phyllotaxy:

Alternate: A single leaf arises at each node in an alternate manner.
Example: China rose, Mustard, Sunflower.
Opposite: A pair of leaves arises at each node and lie opposite to each other.
Example: Calotropis, Guava.
- Opposite decussate: Successive pairs are at right angles to each other. (e.g., Calotropis, Tulsi)
- Opposite superposed: Successive pairs lie in the same plane. (e.g., Guava)
Whorled: More than two leaves arise at a node and form a whorl or circle around the stem.
Example: Alstonia, Nerium.

Diagrams showing types of phyllotaxy: Alternate, Opposite, Whorled

*(Image shows stem segments illustrating alternate leaf arrangement, opposite leaf arrangement, and whorled leaf arrangement)*

Modifications of Leaves

Leaves are modified to perform functions other than photosynthesis.

Leaf Tendrils: The whole leaf or a part of the leaf is modified into a slender, coiled structure that helps the plant to climb.
Example: Pea (whole leaf), Lathyrus aphaca (whole leaf), Glory lily (leaf apex).
Spines: Modified leaves (or sometimes stipules) that are sharp, pointed structures. They serve for protection against grazing animals and also reduce water loss.
Example: Cacti (Opuntia - leaves modified into spines), Ziziphus (stipules modified into spines).
Fleshy Leaves: Leaves become swollen and fleshy due to the storage of food and water.
Example: Onion, Garlic (scale leaves).
Leaf Hooks: Leaflets or leaf parts modified into hooks for climbing. Example: Cat's claw ($Bignonia$).
Phyllode: The petiole expands and becomes flat and green to perform photosynthesis, while the actual leaves are reduced or absent.
Example: Australian Acacia.
Insectivorous Leaves: Leaves modified to trap insects for obtaining nitrogen.
Example: Pitcher plant ($Nepenthes$), Venus flytrap ($Dionaea$).

Diagrams showing leaf modifications: Leaf Tendril (Pea), Spines (Opuntia), Pitcher plant

*(Image shows illustrations of a pea plant with leaf tendrils, a cactus with spines, and a pitcher plant leaf modified into a pitcher)*

The Inflorescence

The arrangement of flowers on the floral axis is termed as inflorescence. The shoot apical meristem changes into a floral meristem when a plant flowers. This change can affect the apex of the stem or a lateral bud.

Depending on whether the apex of the floral axis continues to grow or terminates in a flower, inflorescences are classified into two major types:

Racemose Inflorescence
Cymose Inflorescence

Racemose Inflorescence

In this type of inflorescence, the main axis continues to grow, and the flowers are borne laterally in an acropetal succession. This means that the younger flowers are near the apex (tip), and the older flowers are towards the base.

Examples of racemose types:

Raceme: Main axis is elongated, flowers pedicellate (with stalk). Example: Radish, Mustard.
Spike: Main axis is elongated, flowers sessile (without stalk). Example: Achyranthes.
Spadix: Main axis is fleshy, covered by one or more large bracts called spathes. Flowers sessile. Example: Arum, Banana.
Catkin: A pendulous spike with unisexual flowers. Example: Mulberry, Oak.
Corymb: Main axis is short, lower flowers have longer pedicels than upper ones, bringing all flowers to the same level. Example: Candytuft.
Umbel: Main axis is short, all pedicels of flowers arise from a common point at the base of the involucre of bracts. Example: Coriander, Cumin.
Capitulum or Head: The main axis is flattened (receptacle). Flowers (florets) are sessile and arranged centripetally (youngest at centre, oldest at periphery). Surrounded by an involucre of bracts. Example: Sunflower, Marigold.

Diagrams showing different types of racemose inflorescences (Raceme, Spike, Umbel, Head)

*(Image shows illustrations of Raceme (elongated axis, stalked flowers), Spike (elongated axis, sessile flowers), Umbel (stalks from one point), Head (flattened receptacle with florets))*

Cymose Inflorescence

In this type of inflorescence, the main axis terminates in a flower, so its growth is limited. Flowers are borne in a basipetal succession. This means that the older flowers are at the apex (tip), and the younger flowers are towards the base.

Examples of cymose types:

Solitary Cyme: A single flower at the tip of the axis. Example: Hibiscus, Poppy.
Monochasial Cyme: The main axis ends in a flower, and it produces only one lateral branch at a time, which also terminates in a flower. Example: Heliotropium, Cotton. Can be scorpioid (coiled) or helicoid (spiral).
Dichasial Cyme: The main axis ends in a flower, and it produces two lateral branches at a time below the terminal flower, each terminating in a flower. Example: Jasmine, Teak, Bougainvillea.
Polychasial Cyme: The main axis ends in a flower, and it produces more than two lateral branches at a time below the terminal flower, each terminating in a flower. Example: Calotropis.

Diagrams showing different types of cymose inflorescences (Dichasial Cyme, Monochasial Cyme)

*(Image shows illustrations of Dichasial Cyme (main flower ending axis, two branches below), Monochasial Cyme (main flower ending axis, one branch below))*

Some plants have mixed inflorescences or special types not falling strictly into these two categories.

The Flower

The flower is the reproductive unit of angiosperms (flowering plants). It is essentially a modified shoot where the shoot apical meristem transforms into a floral meristem. The internodes do not elongate, and the axis gets condensed. The apex produces different floral appendages laterally at successive nodes instead of leaves.

A typical flower has a stalk called a pedicel (sessile flowers lack a pedicel). The swollen end of the pedicel is the thalamus or receptacle, which is the base on which the four floral whorls are borne.

The four floral whorls are:

Calyx (sepals) - Outermost whorl.
Corolla (petals) - Second whorl.
Androecium (stamens) - Third whorl (male reproductive part).
Gynoecium (carpels/pistil) - Innermost whorl (female reproductive part).

When calyx and corolla are not distinct, they are collectively called perianth (e.g., in lily).

A flower with both androecium and gynoecium is bisexual. A flower having either only androecium or only gynoecium is unisexual.

Symmetry of Flower

Flowers can show different types of symmetry:

Actinomorphic (Radial symmetry): The flower can be divided into two equal radial halves by any radial plane passing through the centre. It is represented by $\oplus$ or $\ast$.
Example: Mustard, Datura, Chilli.
Zygomorphic (Bilateral symmetry): The flower can be divided into two similar halves only by a single vertical plane. It is represented by $\%$ or $\uparrow$.
Example: Pea, Gulmohur, Bean, Cassia.
Asymmetrical (Irregular): The flower cannot be divided into two equal halves by any plane.
Example: Canna.

Relation of Floral Parts to Ovary

Based on the position of the calyx, corolla, and androecium in relation to the ovary on the thalamus, flowers are classified into three types:

Hypogynous: The gynoecium (ovary) is positioned highest, and other floral parts are situated below the ovary. The ovary is said to be superior.
Example: Mustard, China rose, Brinjal.
Perigynous: The gynoecium is situated in the centre, and other floral parts are located on the rim of the thalamus, at the same level as the ovary. The ovary is said to be half inferior.
Example: Plum, Rose, Peach.
Epigynous: The margin of the thalamus grows upwards enclosing the ovary completely and getting fused with it. The other floral parts arise above the ovary. The ovary is said to be inferior.
Example: Guava, Cucumber, Ray florets of Sunflower.

Diagrams showing floral arrangements relative to ovary: Hypogynous (superior ovary), Perigynous (half inferior ovary), Epigynous (inferior ovary)

*(Image shows longitudinal sections of flowers illustrating the attachment points of calyx, corolla, and androecium relative to the ovary's position on the thalamus)*

Calyx

The calyx is the outermost whorl of the flower. It is composed of units called sepals. Sepals are usually green and leaf-like.

Shape and arrangement of sepals:

Gamosepalous: Sepals are united (fused).
Polysepalous: Sepals are free.

Function of calyx: Protects the flower in the bud stage.

Corolla

The corolla is the whorl inner to the calyx. It is composed of units called petals. Petals are usually brightly coloured to attract insects for pollination.

Shape and arrangement of petals:

Gamopetalous: Petals are united (fused).
Polypetalous: Petals are free.

The shape and colour of the corolla vary greatly (tubular, funnel-shaped, wheel-shaped, etc.).

Aestivation

Aestivation is the mode of arrangement of sepals or petals in the floral bud with respect to the other members of the same whorl.

Types of aestivation:

Valvate: Sepals or petals in a whorl just touch one another at the margin, without overlapping.
Example: Calotropis.
Twisted: One margin of the appendage overlaps that of the next one, and so on.
Example: China rose, Lady's finger, Cotton.
Imbricate: The margins of sepals or petals overlap one another, but not in a particular direction.
Example: Cassia, Gulmohur.
Vexillary (Papilionaceous): Found in pea and bean flowers. The largest petal (standard or vexillum) overlaps the two lateral petals (wings or alae), which in turn overlap the two smallest anterior petals (keel or carina).

*(Image shows cross-section diagrams illustrating the arrangement of petals/sepals in bud for Valvate, Twisted, Imbricate, and Vexillary aestivation)*

Androecium

The androecium is the male reproductive part of the flower, composed of stamens. Each stamen consists of two parts: a filament (stalk) and an anther (usually bilobed, containing pollen sacs).

Pollen grains, containing the male gametes, are produced in the pollen sacs.

A sterile stamen (unable to produce pollen) is called a staminode.

Stamens may be attached to other parts:

Epipetalous: Stamens are attached to the petals. Example: Brinjal.
Epiphyllous: Stamens are attached to the perianth (when calyx and corolla are not distinct). Example: Lily.

Stamens can be united in different ways:

Adhesion (Fusion of stamens among themselves):
- Monoadelphous: Stamens are united into a single bundle or tube. Example: China rose.
- Diadelphous: Stamens are united into two bundles. Example: Pea.
- Polyadelphous: Stamens are united into more than two bundles. Example: Citrus.

Variation in the length of filaments within a flower also occurs (e.g., Salvia, Mustard).

Gynoecium

The gynoecium is the female reproductive part of the flower, composed of one or more carpels. Each carpel usually consists of three parts:

Stigma: Receptive surface for pollen grains, usually at the tip of the pistil.
Style: A slender stalk connecting the stigma to the ovary.
Ovary: The swollen basal part containing one or more ovules. The ovules are attached to a flattened cushion-like structure called the placenta.

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

If there is a single carpel, the gynoecium is monocarpellary. If there are more than one carpels, it can be:

Apocarpous: Carpels are free. Example: Lotus, Rose.
Syncarpous: Carpels are united (fused). Example: Tomato, Mustard.

Placentation

The arrangement of ovules within the ovary is called placentation.

Types of placentation:

Marginal: The placenta forms a ridge along the ventral suture of the ovary, and the ovules are borne on this ridge, forming two rows. Ovary is usually monocarpellary.
Example: Pea.
Axile: The placenta is axial, and the ovules are attached to it in a multilocular (chambered) ovary. Ovary is syncarpous.
Example: China rose, Tomato, Lemon.
Parietal: The ovules develop on the inner wall of the ovary or on peripheral part. The ovary is usually unilocular (single chambered) but may become two-chambered due to the formation of a false septum (replum).
Example: Mustard, Argemone.
Free Central: The ovules are borne on a central axis, and there are no septa (divisions) in the ovary. Ovary is unilocular.
Example: Dianthus, Primrose.
Basal: The placenta develops at the base of the ovary, and a single ovule is attached to it. Ovary is unilocular.
Example: Sunflower, Marigold.

*(Image shows cross-section diagrams illustrating the arrangement of ovules on the placenta within the ovary for each type of placentation)*

The Fruit

The fruit is the mature or ripened ovary, developed after fertilisation. It is a characteristic feature of flowering plants (angiosperms).

If a fruit is formed without fertilisation of the ovary, it is called a parthenocarpic fruit. Parthenocarpic fruits are typically seedless (e.g., banana).

Parts of a Fruit

A fruit generally consists of a pericarp (fruit wall) and seeds.

The pericarp develops from the ovary wall and may be dry or fleshy. When the pericarp is fleshy, it is differentiated into three layers:

Epicarp: The outermost layer, forming the skin of the fruit.
Mesocarp: The middle layer. It may be fleshy and edible (e.g., mango, peach) or fibrous (e.g., coconut).
Endocarp: The innermost layer. It is often hard and stony (e.g., mango, coconut) or membranous.

Diagram showing parts of a fleshy fruit (e.g., Mango) with epicarp, mesocarp, endocarp, and seed

*(Image shows a longitudinal section of a mango fruit highlighting the three layers of the pericarp and the seed inside the hard endocarp)*

Types of Fruits (Simplified based on development)

Fruits can be broadly classified into Simple, Aggregate, and Multiple fruits.

Simple Fruits: Develop from a single flower with a single ovary.
- Fleshy Fruits: Pericarp is fleshy and juicy.
  - Drupe: Develops from a monocarpellary (or multicarpellary syncarpous) superior ovary. Typically one-seeded. Pericarp differentiated into epicarp (skin), fleshy mesocarp, and stony endocarp.
    Example: Mango, Coconut, Plum, Peach.
    
    In coconut (a drupe), the mesocarp is fibrous, not fleshy.
  - Berry: Develops from a superior or inferior ovary. Pericarp usually not differentiated into distinct layers; outer skin (epicarp), fleshy mesocarp and endocarp containing many seeds.
    Example: Tomato, Grapes, Brinjal.
  - Pome: Develops from an inferior ovary. The edible part is the fleshy thalamus, while the actual fruit (core containing seeds) is inside. Example: Apple, Pear. (Sometimes called a false fruit).
- Dry Fruits: Pericarp is dry and not differentiated into layers. Can be dehiscent (splitting open to release seeds) or indehiscent (not splitting open). Example: Pea pod (dehiscent legume), Mustard (dehiscent siliqua), Rice/Wheat (indehiscent caryopsis), Groundnut (indehiscent pod), Mango seed (indehiscent nut inside endocarp).
Aggregate Fruits: Develop from a single flower having an apocarpous gynoecium (multiple free carpels). Each carpel develops into a fruitlet, and the collection of fruitlets forms the aggregate fruit. Example: Custard apple (aggregate of berries), Strawberry (aggregate of achenes on fleshy thalamus), Raspberry (aggregate of drupes).
Multiple (Composite) Fruits: Develop from the entire inflorescence. The flowers of the inflorescence fuse along with their surrounding structures to form a single fruit.
Example: Pineapple (Spadix inflorescence), Mulberry (Catkin inflorescence), Jackfruit (Spadix inflorescence).

The Seed

The seed is the ripened ovule, developed after fertilisation. It contains an embryo, which is the potential new plant, usually stored food, and a protective seed coat. It is a vital part of sexual reproduction in plants.

A seed typically consists of a seed coat and an embryo.

The seed coat develops from the integuments of the ovule. The embryo develops from the zygote.

The embryo consists of an embryonal axis and one or two cotyledons.

The embryonal axis has a plumule (gives rise to the shoot) and a radicle (gives rise to the root).

Albuminous vs. Non-albuminous Seeds

Non-albuminous (Exalbuminous) seeds: Endosperm is completely consumed by the embryo during seed development. The stored food is in the cotyledons.
Example: Pea, Bean, Groundnut.
Albuminous seeds: Endosperm is retained and used as food storage tissue during seed germination.
Example: Wheat, Maize, Rice, Castor.

Structure of a Dicotyledonous Seed

Let's consider a typical non-albuminous dicot seed like that of Pea or Bean.

Seed Coat: The outermost covering. It has two layers: the outer testa and the inner tegmen.
On the seed coat, there is a scar called the hilum, through which the developing ovule was attached to the fruit.
Just above the hilum is a small pore called the micropyle, which facilitates the entry of water and oxygen during germination.
Embryo: Located inside the seed coat. It consists of the embryonal axis and two cotyledons.
- Cotyledons: Two large, fleshy structures that store food (in non-albuminous seeds).
- Embryonal Axis: The part of the embryo that will grow into the plant. It has:
  - Plumule: Located above the point of attachment of cotyledons, will develop into the shoot (stem, leaves).
  - Radicle: Located below the point of attachment of cotyledons, will develop into the root.
Endosperm is absent in non-albuminous seeds.

Diagram showing the structure of a dicot seed (e.g., Pea)

*(Image shows a dicot seed (like pea), highlighting seed coat (testa, tegmen), hilum, micropyle, and inside structure showing two cotyledons and the embryonal axis with plumule and radicle)*

Structure of Monocotyledonous Seed

Let's consider a typical albuminous monocot seed like that of Maize.

Monocotyledonous seeds are usually albuminous (with endosperm), but some are non-albuminous (e.g., orchids).
In cereals like maize, the fruit wall is fused with the seed coat, so the seed is essentially a fruit called a caryopsis.
Endosperm: The large, bulky storage tissue. It is separated from the embryo by a proteinaceous layer called the aleurone layer, which is 1-2 cell layers thick and rich in proteins.
Embryo: Small and located in a furrow at one end of the endosperm. It consists of:
- Scutellum: A single, large, shield-shaped cotyledon located on one side of the embryonal axis. It helps in the translocation of food from the endosperm to the developing embryo during germination.
- Embryonal Axis: Has a plumule and a radicle.
  - The plumule is enclosed in a protective sheath called the coleoptile.
  - The radicle is enclosed in a protective sheath called the coleorhiza.

Diagram showing the structure of a monocot seed (e.g., Maize)

*(Image shows a maize grain cross-section highlighting fused fruit wall and seed coat, endosperm, aleurone layer, scutellum, and embryonal axis with coleoptile and coleorhiza)*

Semi-Technical Description of a Typical Flowering Plant

To describe a flowering plant scientifically, we use a set of standard botanical terms to provide a semi-technical description. This allows for clear and concise communication about the plant's characteristics and helps in its identification.

The description usually starts with the habitat, habit, and vegetative characters, followed by floral characters.

Sequence of Description

Habitat and Habit: Where it grows (habitat) and its overall form (herb, shrub, tree, climber).
Vegetative Characters:
- Root: Type (tap, fibrous, adventitious), modifications.
- Stem: Type (herbaceous, woody, underground, aerial), presence/absence of nodes/internodes, modifications.
- Leaf: Type (simple, compound), venation (reticulate, parallel), phyllotaxy (alternate, opposite, whorled), presence/absence of stipules, shape of lamina, margin, apex, modifications.
Floral Characters:
- Inflorescence: Type (racemose, cymose, or special).
- Flower: Type (bisexual, unisexual), symmetry (actinomorphic, zygomorphic), number of floral parts (trimerous, tetramerous, pentamerous), position of ovary (hypogynous, perigynous, epigynous), colour, fragrance.
- Calyx: Number of sepals, united (gamosepalous) or free (polysepalous), aestivation.
- Corolla: Number of petals, united (gamopetalous) or free (polypetalous), shape, aestivation.
- Perianth: (If calyx and corolla are not distinct) Number of tepals, united or free, aestivation, epiphyllous stamens.
- Androecium: Number of stamens, length of filaments, attachment to petals/perianth (epipetalous/epiphyllous), fusion (monoadelphous, diadelphous, polyadelphous).
- Gynoecium: Number of carpels, free (apocarpous) or united (syncarpous), number of chambers (locules) in the ovary, number of ovules per locule, placentation, style (number, length), stigma (type).
Fruit: Type (simple - drupe, berry, capsule, etc., aggregate, multiple).
Seed: Albuminous or non-albuminous.
Floral Formula: A symbolic representation summarizing the floral characters.
Floral Diagram: A graphical representation showing the relative positions and arrangement of floral parts.

Floral Formula

The floral formula is represented using standard symbols:

Br: Bracteate (bracts present)
Ebr: Ebracteate (bracts absent)
$\oplus$ or $\ast$: Actinomorphic symmetry
$\%$ or $\uparrow$: Zygomorphic symmetry
$\P$: Perianth (when calyx and corolla are not distinct)
K: Calyx (number of sepals written after K; if united, put number in parenthesis, e.g., K(5))
C: Corolla (number of petals; if united, C(5))
A: Androecium (number of stamens; if united, A(5); if in bundles, A($\infty$))
G: Gynoecium (number of carpels; if united, G(2))
Number written below the symbol represents the count of that floral part (e.g., K5 means 5 sepals).
Fusion is indicated by enclosing the number in parenthesis $(...)$.
Adhesion (e.g., stamens attached to petals) is indicated by a line drawn above the symbols of the adhered parts (e.g., C A ).
G$\underline{\hspace{0.5cm}}$: Superior ovary (Hypogynous flower)
$\overline{\text{G}}$: Inferior ovary (Epigynous flower)
$\text{G}$: Half inferior ovary (Perigynous flower)
$\sigma$ or $\text{♂}$: Male flower
$\text{♀}$: Female flower
$\text{⚥}$ or $\text{⚲}$: Bisexual flower

Example Floral Formula (Hypothetical): $\oplus \text{⚥}$ K(5) C5 A10 G$\underline{(2)}$

This formula represents: Actinomorphic, bisexual flower with 5 united sepals, 5 free petals, 10 stamens, and a syncarpous gynoecium of 2 carpels with superior ovary.

Floral Diagram

A floral diagram is a plan of a flower showing the arrangement of the floral whorls and their relation to each other and to the mother axis.

The mother axis (representing the stem or inflorescence axis) is shown as a dot at the top of the diagram.
The calyx is the outermost whorl, then corolla, androecium, and gynoecium is in the centre.
Parts of each whorl are depicted by specific shapes (e.g., sepals, petals, stamens, carpels).
Fusion of parts is shown by connecting lines between the structures.
Aestivation is indicated by the relative positions and overlapping of the margins of sepals/petals.
The position of the ovary (superior/inferior) is not directly shown in the diagram but is indicated by the floral formula.

Generic diagram showing the structure of a floral diagram with mother axis, sepals, petals, stamens, and carpels

*(Image shows a top-down view of a simplified flower cross-section with mother axis dot above, outermost whorl (sepals), second whorl (petals), third whorl (stamens), and central structure (carpels/ovary))*

Description of Some Important Families

Studying representative families helps understand the diversity and relationships among flowering plants. Here, we describe a few important families based on their vegetative and floral characters.

Fabaceae

This family was earlier called Papilionoideae, a sub-family of family Leguminosae. It is distributed all over the world.

Vegetative Characters:

Habit: Herbs, shrubs, climbers; sometimes small trees.
Root: Tap root, usually with root nodules containing nitrogen-fixing bacteria (Rhizobium).
Stem: Erect or climber.
Leaf: Alternate phyllotaxy, pinnately compound or simple; leaf base pulvinate; stipulate; venation reticulate.

Floral Characters:

Inflorescence: Racemose.
Flower: Bisexual, zygomorphic.
Calyx: 5 sepals, gamosepalous (united), valvate or imbricate aestivation.
Corolla: 5 petals, polypetalous (free); vexillary aestivation (a large standard, two lateral wings, two fused anterior petals forming keel).
Androecium: 10 stamens, diadelphous (9 fused + 1 free) or sometimes monoadelphous; anther dithecous.
Gynoecium: Monocarpellary, ovary superior, unilocular, many ovules; single short style, hairy stigma; placentation marginal.

Floral Formula:

$\% \text{⚥}$ K(5) C $1+2+(2)$ A $9+1$ or (10) G$\underline{1}$

Floral Diagram:

*(Image shows floral diagram of Fabaceae with mother axis, sepals (fused), petals (vexillary arrangement), stamens (diadelphous), monocarpellary ovary with marginal placentation)*

Economic Importance:

Pulses: Gram ($Cicer$), Arhar ($Cajanus$), Sem ($Dolichos$), Moong ($Vigna \: radiata$), Pea ($Pisum$), Lentil ($Lens$).
Edible oil: Groundnut ($Arachis \: hypogaea$), Soybean ($Glycine \: max$).
Dyes: Indigofera.
Fibres: Sun hemp ($Crotalaria \: juncea$).
Fodder: Sesbania, Trifolium ($Trifolium$), Melilotus ($Melilotus$).
Ornamentals: Lupin ($Lupinus$), Sweet pea ($Lathyrus$).
Medicine: Muliathi ($Glycyrrhiza \: glabra$).

Solanaceae

This family is commonly called the 'Potato family'. It is a large family, widely distributed in tropical, subtropical, and even temperate zones.

Vegetative Characters:

Habit: Herbs, shrubs, and occasionally small trees.
Stem: Herbaceous or woody, aerial, erect, cylindrical, branched, solid or hollow, hairy or glabrous. Underground stem modifications (e.g., potato tuber).
Leaf: Alternate phyllotaxy; simple, rarely pinnately compound; exstipulate; venation reticulate.

Floral Characters:

Inflorescence: Solitary, axillary, or cymose as in Solanum.
Flower: Bisexual, actinomorphic.
Calyx: 5 sepals, united (gamosepalous); persistent (remains attached to fruit); valvate aestivation.
Corolla: 5 petals, united (gamopetalous); tube-like or funnel-shaped or wheel-shaped; valvate aestivation.
Androecium: 5 stamens; epipetalous (attached to petals); anther dithecous.
Gynoecium: Bicarpellary, syncarpous (united carpels); ovary superior; bilocular (two-chambered); placenta is swollen with many ovules; axile placentation. Obliquely placed septum in the ovary.

Floral Formula:

$\oplus \text{⚥}$ K(5) C(5) A5 G$\underline{(2)}$

Floral Diagram:

*(Image shows floral diagram of Solanaceae with mother axis, sepals (fused), petals (fused), stamens (epipetalous), bicarpellary ovary (fused) with two locules and axile placentation, often showing oblique septum)*

Economic Importance:

Food: Tomato ($Lycopersicon \: esculentum$), Brinjal ($Solanum \: melongena$), Potato ($Solanum \: tuberosum$), Chilli ($Capsicum \: annuum$).
Spice: Chilli.
Medicine: Belladonna ($Atropa \: belladonna$), Ashwagandha ($Withania \: somnifera$), Datura ($Datura \: stramonium$).
Fumigatory: Tobacco ($Nicotiana \: tabacum$).
Ornamentals: Petunia.

Liliaceae

This family is commonly called the 'Lily family'. It is a characteristic family of monocotyledonous plants, distributed worldwide.

Vegetative Characters:

Habit: Perennial herbs with underground bulbs, corms, or rhizomes.
Root: Adventitious fibrous roots.
Stem: Underground (bulb, corm, rhizome). Aerial shoots may be present.
Leaf: Mostly radical (arising from the base), alternate; linear, parallel venation; exstipulate.

Floral Characters:

Inflorescence: Solitary (single flower) or cymose; often a raceme in some cases.
Flower: Bisexual, actinomorphic, hypogynous (superior ovary).
Perianth ($\P$): 6 tepals (when calyx and corolla are not distinct), arranged in two whorls of 3 each ($3+3$). Tepals often united into a tube; valvate aestivation.
Androecium: 6 stamens, arranged in two whorls of 3 each ($3+3$); epiphyllous (attached to tepals); anther dithecous.
Gynoecium: Tricarpellary, syncarpous (united carpels); ovary superior; trilocular (three-chambered) with many ovules; axile placentation.
Fruit: Capsule (usually) or berry (rarely).
Seed: Albuminous.

Floral Formula:

$\oplus \text{⚥}$ $\P_{3+3}$ A$_{3+3}$ G$\underline{(3)}$

Or, if tepals are united: $\oplus \text{⚥}$ $\P_{(3+3)}$ A$_{3+3}$ G$\underline{(3)}$ (with a line over $\P$ and A for epiphyllous)

$\oplus \text{⚥}$ $\overline{\P_{(3+3)} \text{ A}_{3+3}}$ G$\underline{(3)}$

Floral Diagram:

*(Image shows floral diagram of Liliaceae with mother axis, 6 tepals in two whorls, 6 stamens in two whorls (epiphyllous), tricarpellary ovary (fused) with three locules and axile placentation)*

Economic Importance:

Ornamentals: Tulip ($Tulipa$), Gloriosa, Lily ($Lilium$).
Food: Asparagus, Onion ($Allium \: cepa$), Garlic ($Allium \: sativum$).
Medicine: Aloe ($Aloe \: vera$).
Source of Colchicine: Colchicum autumnale (used in cell division studies).