Class 11 Biology NCERT Notes- Chapter 5: Morphology of Flowering Plants | EKADEMY | Online Courses, Live Classes, Lessons & Quizzes

Detailed Study Notes – Chapter 5: Morphology of Flowering Plants( Class 11 Biology, Notes, PDFs, Quizzes, MCQs)

Introduction to Plant Morphology

The study of the diverse forms of life on Earth, including flowering plants (angiosperms), began with observation of their gross structural features, both external and internal. This descriptive approach, known as natural history, laid the groundwork for modern experimental biology, physiology, and evolutionary biology. Understanding the morphology—the study of the external structure of plants—is essential for classification and for comprehending plant adaptations to various environments for functions like protection, climbing, and storage.

Despite the vast diversity in their external structure, all angiosperms are characterized by the presence of roots, stems, leaves, flowers, and fruits. A typical flowering plant is divided into two main systems:

The Root System: The underground part of the plant.
The Shoot System: The portion of the plant above the ground, which includes the stem, leaves, flowers, and fruits.

Katherine Esau (1898 – 1997)

A prominent figure in plant biology, Katherine Esau made significant contributions to the field of plant anatomy. Born in Ukraine, she received her doctorate in the United States in 1931. Her research revealed that the curly top virus spreads through a plant’s food-conducting tissue, the phloem. Her 1954 book, Plant Anatomy, and her 1960 publication, The Anatomy of Seed Plants (often called the “Webster’s of plant biology”), revived the discipline with a dynamic, developmental approach. Esau was elected to the National Academy of Sciences in 1957 and received the National Medal of Science in 1989.

1. The Root System

The root system is the descending, typically underground part of the plant axis.

1.1 Types of Root Systems

Tap Root System: Found in the majority of dicotyledonous plants (e.g., mustard). The primary root develops directly from the elongation of the radicle (the embryonic root). It grows deep into the soil and gives rise to lateral roots of several orders (secondary, tertiary, etc.). The primary root and its branches constitute the tap root system.
Fibrous Root System: Characteristic of monocotyledonous plants (e.g., wheat). The primary root is short-lived and is replaced by a large number of roots that originate from the base of the stem.
Adventitious Roots: These roots arise from parts of the plant other than the radicle. Examples include grass, Monstera, and the banyan tree.

1.2 Functions of the Root

Absorption of water and minerals from the soil.
Providing proper anchorage to the plant parts.
Storing reserve food material.
Synthesis of plant growth regulators.

1.3 Regions of the Root

The root tip is divided into distinct regions:

Root Cap: A thimble-like structure covering the root apex, protecting the tender tip as it navigates through the soil.
Region of Meristematic Activity: Located a few millimeters above the root cap. The cells in this region are small, thin-walled, have dense protoplasm, and divide repeatedly.
Region of Elongation: Proximal to the meristematic region. Cells here undergo rapid elongation and enlargement, which is responsible for the growth of the root in length.
Region of Maturation: Proximal to the region of elongation. Cells in this zone differentiate and mature. Epidermal cells in this region form very fine, delicate, thread-like root hairs, which are the primary sites for water and mineral absorption.

2. The Stem

The stem is the ascending part of the plant axis, developing from the plumule of the embryo. It is typically green when young and becomes woody and dark brown with age.

2.1 Characteristics of the Stem

Nodes: Regions on the stem where leaves are borne.
Internodes: The portions of the stem between two nodes.
Buds: The stem bears buds, which can be terminal (at the tip) or axillary (in the axil of leaves).
Positive Phototropism: Stems generally grow towards light.

2.2 Functions of the Stem

Spreading out branches, leaves, flowers, and fruits.
Conducting water, minerals, and photosynthates (food produced during photosynthesis).
Specialized functions in some plants include food storage, support, protection, and vegetative propagation.

3. The Leaf

The leaf is a lateral, generally flattened structure borne on the stem at a node. It is the most important vegetative organ for photosynthesis.

3.1 Structure of a Typical Leaf

Leaf Base: The part of the leaf attached to the stem. It may bear two small leaf-like structures called stipules. In monocots, the leaf base often expands into a sheath that covers the stem. In some leguminous plants, the leaf base becomes swollen and is called a pulvinus.
Petiole: The stalk that connects the leaf blade to the stem. It helps hold the blade up to the light. Flexible petioles allow the leaf to flutter, cooling it and bringing fresh air to its surface.
Lamina (Leaf Blade): The green, expanded part of the leaf. It is traversed by veins and veinlets, with a prominent middle vein called the midrib. Veins provide rigidity and act as channels for transporting water, minerals, and food.

3.2 Venation

Venation is the arrangement of veins and veinlets in the lamina.

Reticulate Venation: Veinlets form a network. This is typical of dicotyledonous plants.
Parallel Venation: Veins run parallel to each other. This is characteristic of most monocotyledonous plants.

3.3 Types of Leaves

Simple Leaf: The lamina is entire or, if incised, the incisions do not reach the midrib.
Compound Leaf: The incisions of the lamina reach the midrib, breaking it into a number of leaflets.
- Pinnately Compound Leaf: Leaflets are present on a common axis called the rachis (which represents the midrib). Example: neem.
- Palmately Compound Leaf: Leaflets are attached at a common point, at the tip of the petiole. Example: silk cotton.

3.4 Phyllotaxy

Phyllotaxy is the pattern of arrangement of leaves on a stem or branch.

Alternate: A single leaf arises at each node in an alternate manner. Examples: china rose, mustard, sun flower.
Opposite: A pair of leaves arises at each node, opposite to each other. Examples: Calotropis, guava.
Whorled: More than two leaves arise at a node and form a whorl. Example: Alstonia.

4. The Inflorescence

The arrangement of flowers on the floral axis is termed inflorescence. A flower is a modified shoot where the shoot apical meristem changes to a floral meristem.

Racemose Inflorescence: The main axis continues to grow indefinitely. Flowers are borne laterally in an acropetal succession (older flowers are at the base, younger ones are at the apex).
Cymose Inflorescence: The main axis terminates in a flower, limiting its growth. Flowers are borne in a basipetal order (older flowers are at the apex, younger ones are at the base).

5. The Flower

The flower is the reproductive unit in angiosperms, designed for sexual reproduction. A typical flower has four whorls arranged on the thalamus (or receptacle), the swollen end of the stalk (pedicel).

Accessory Organs: Calyx and Corolla.
Reproductive Organs: Androecium and Gynoecium.
Perianth: In flowers like the lily, where the calyx and corolla are not distinct, they are collectively termed the perianth.

5.1 Flower Characteristics

Sexuality:
- Bisexual: Has both androecium and gynoecium.
- Unisexual: Has either only stamens (male) or only carpels (female).
Symmetry:
- Actinomorphic (Radial): Can be divided into two equal halves in any radial plane passing through the center. Examples: mustard, datura, chilli.
- Zygomorphic (Bilateral): Can be divided into two similar halves in only one particular vertical plane. Examples: pea, gulmohur, bean, Cassia.
- Asymmetric (Irregular): Cannot be divided into two similar halves by any vertical plane. Example: canna.
Floral Appendages:
- Trimerous, Tetramerous, Pentamerous: Floral appendages are in multiples of 3, 4, or 5, respectively.
Bracts:
- Bracteate: A flower with bracts (reduced leaves at the base of the pedicel).
- Ebracteate: A flower without bracts.

5.2 Position of Floral Parts on Thalamus

This describes the position of the calyx, corolla, and androecium with respect to the ovary.

Hypogynous Flower (Superior Ovary): The gynoecium occupies the highest position, with other parts situated below it. Examples: mustard, china rose, brinjal.
Perigynous Flower (Half-Inferior Ovary): The gynoecium is in the center, and other floral parts are located on the rim of the thalamus at almost the same level. Examples: plum, rose, peach.
Epigynous Flower (Inferior Ovary): The margin of the thalamus grows upward, enclosing the ovary completely and fusing with it. Other floral parts arise above the ovary. Examples: guava, cucumber, ray florets of sunflower.

5.3 Parts of a Flower

Calyx: The outermost whorl, composed of sepals. Sepals are typically green and protect the flower in the bud stage.
- Gamosepalous: Sepals are united.
- Polysepalous: Sepals are free.
Corolla: Composed of petals, which are usually brightly colored to attract pollinators.
- Gamopetalous: Petals are united.
- Polypetalous: Petals are free.
- Shapes: Can be tubular, bell-shaped, funnel-shaped, or wheel-shaped.
Aestivation: The mode of arrangement of sepals or petals in a floral bud.
- Valvate: Margins just touch one another without overlapping. Example: Calotropis.
- Twisted: One margin of an appendage overlaps the next one in a regular pattern. Examples: china rose, lady’s finger, cotton.
- Imbricate: Margins overlap but not in any particular direction. Examples: Cassia, gulmohur.
- Vexillary (Papilionaceous): Found in pea/bean flowers with five petals. The largest petal (standard) overlaps two lateral petals (wings), which in turn overlap the two smallest anterior petals (keel).
Androecium: The male reproductive part, composed of stamens. Each stamen has a stalk (filament) and an anther, which contains pollen sacs where pollen grains are produced. A sterile stamen is a staminode.
- Adhesion:
  - Epipetalous: Stamens are attached to the petals (e.g., brinjal).
  - Epiphyllous: Stamens are attached to the perianth (e.g., lily).
- Cohesion:
  - Polyandrous: Stamens are free.
  - Monoadelphous: Stamens are united into one bundle (e.g., china rose).
  - Diadelphous: Stamens are united into two bundles (e.g., pea).
  - Polyadelphous: Stamens are united into more than two bundles (e.g., citrus).
Gynoecium: The female reproductive part, made of one or more carpels. A carpel consists of a stigma (receptive surface for pollen), a style (connective tube), and an ovary (enlarged basal part containing ovules).
- Cohesion:
  - Apocarpous: Carpels are free (e.g., lotus, rose).
  - Syncarpous: Carpels are fused (e.g., mustard, tomato).
Placentation: The arrangement of ovules within the ovary.
- Marginal: Placenta forms a ridge along the ventral suture, with ovules in two rows (e.g., pea).
- Axile: Placenta is axial, and ovules are attached in a multilocular ovary (e.g., china rose, tomato, lemon).
- Parietal: Ovules develop on the inner wall of a one-chambered ovary (e.g., mustard, Argemone).
- Free Central: Ovules are borne on a central axis, and septa are absent (e.g., Dianthus, Primrose).
- Basal: Placenta develops at the base of the ovary, with a single ovule attached (e.g., sunflower, marigold).

6. The Fruit

The fruit is a mature or ripened ovary that develops after fertilization. It is a characteristic feature of flowering plants.

Parthenocarpic Fruit: A fruit formed without fertilization of the ovary.
Pericarp: The fruit wall, which can be dry or fleshy. In fleshy fruits, it is differentiated into:
- Epicarp: Outer layer.
- Mesocarp: Middle layer.
- Endocarp: Inner layer.
Drupe: A type of fruit that develops from a monocarpellary superior ovary and is one-seeded.
- Mango: The pericarp is well-differentiated into a thin epicarp, a fleshy edible mesocarp, and a stony hard endocarp.
- Coconut: The mesocarp is fibrous.

7. The Seed

After fertilization, ovules develop into seeds. A seed consists of a seed coat and an embryo.

Embryo: Composed of a radicle (embryonic root), a plumule (embryonic shoot), an embryonal axis, and one (monocot) or two (dicot) cotyledons.
Endospermic (Albuminous) Seeds: Have endosperm, a food-storing tissue formed from double fertilization (e.g., castor, maize).
Non-endospermic (Exalbuminous) Seeds: Endosperm is not present in the mature seed as it is consumed during development (e.g., bean, gram, pea).

7.1 Structure of a Dicotyledonous Seed

Seed Coat: The outermost covering with two layers: the outer testa and inner tegmen.
Hilum: A scar where the seed was attached to the fruit.
Micropyle: A small pore above the hilum.
Embryo: Consists of an embryonal axis and two fleshy cotyledons full of reserve food.

7.2 Structure of a Monocotyledonous Seed

Seed Coat: Membranous and generally fused with the fruit wall (pericarp).
Endosperm: Bulky and stores food. Its outer covering is a proteinous layer called the aleurone layer.
Embryo: Small and situated in a groove. It consists of:
- Scutellum: One large, shield-shaped cotyledon.
- Coleoptile: A sheath enclosing the plumule.
- Coleorhiza: A sheath enclosing the radicle.

8. Semi-technical Description of a Flowering Plant

A standardized description of a flowering plant follows a sequence: habit, vegetative characters (root, stem, leaves), and then floral characters (inflorescence and flower parts). This is summarized using a floral formula and a floral diagram.

Floral Formula Symbols:
- Br: Bracteate
- K: Calyx
- C: Corolla
- P: Perianth
- A: Androecium
- G: Gynoecium
- G (line below): Superior Ovary
- G (line above): Inferior Ovary
- ⊕: Actinomorphic
- %: Zygomorphic (symbol not shown in text, but implied)
- ♂: Male
- ♀: Female
- ( ): Fusion of parts
- Arc above symbols: Adhesion between whorls
Floral Diagram: Provides information on the number of parts, their arrangement, and their relation to each other and the mother axis (represented by a dot).

9. Description of Solanaceae (Potato Family)

Distribution: Widely found in tropics, subtropics, and temperate zones.
Vegetative Characters:
- Habit: Mostly herbs and shrubs, rarely small trees.
- Stem: Herbaceous, sometimes woody, aerial, erect, cylindrical, branched, solid or hollow, hairy or glabrous. Underground stem in potato (Solanum tuberosum).
- Leaves: Alternate, simple (rarely pinnately compound), exstipulate, with reticulate venation.
Floral Characters:
- Inflorescence: Solitary, axillary or cymose (as in Solanum).
- Flower: Bisexual, actinomorphic.
- Calyx: Five united sepals (gamosepalous), persistent, valvate aestivation.
- Corolla: Five united petals (gamopetalous), valvate aestivation.
- Androecium: Five stamens, epipetalous.
- Gynoecium: Bicarpellary, syncarpous, ovary superior, bilocular, placenta swollen with many ovules, axile placentation.
- Fruit: Berry or capsule.
- Seeds: Many, endospermous.
Floral Formula: ⊕ ♀ K(5) C(5) A5 G(2) (with adhesion between C and A)
Economic Importance: Source of food (tomato, brinjal, potato), spice (chilli), medicine (belladonna, ashwagandha), fumigatory (tobacco), and ornamentals (petunia).

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Quiz

Short-Answer Questions (Answer in 2-3 sentences)

What are the two primary systems of a flowering plant?
Define morphology and explain its importance in biology.
Differentiate between a tap root system and a fibrous root system.
What are adventitious roots? Provide an example.
List the four main functions of the root system.
Name and describe the function of the root cap.
What is the primary function of the region of meristematic activity in a root tip?
How can a stem be distinguished from a root based on its structural features?
Explain the role of the petiole in a leaf.
What is a pulvinus and in which type of plants is it typically found?
Differentiate between reticulate and parallel venation.
How is a simple leaf different from a compound leaf?
Define phyllotaxy and name its three main types.
Distinguish between racemose and cymose inflorescence based on the growth of the main axis.
What is the difference between an actinomorphic and a zygomorphic flower?
Describe a hypogynous flower and state the position of its ovary.
What is aestivation? Name the four main types.
Explain the term ‘epipetalous’ as it relates to stamens.
What is the difference between an apocarpous and a syncarpous gynoecium?
Define placentation and list two different types with examples.
What is a parthenocarpic fruit?
Describe the pericarp of a mango.
What are the two layers of a seed coat in a dicot seed?
What is the function of the aleurone layer in a monocot seed?
What information is conveyed by a floral formula?

Multiple-Choice Questions (MCQs)

In monocotyledonous plants like wheat, the primary root is short-lived and replaced by roots originating from the base of the stem. This is called a: a) Tap root system b) Adventitious root system c) Fibrous root system d) Haustorial root system
The region of the root responsible for growth in length is the: a) Region of maturation b) Region of elongation c) Root cap d) Region of meristematic activity
The arrangement of leaves on a stem where a pair of leaves arises at each node opposite each other is called: a) Alternate b) Whorled c) Opposite d) Basal
A leaf in which the leaflets are attached at a common point at the tip of the petiole, as in silk cotton, is called: a) Pinnately compound b) Simple c) Palmately compound d) Decompound
In a cymose inflorescence, the flowers are borne in what order? a) Acropetal b) Centrifugal c) Centripetal d) Basipetal
Which of the following is an example of a plant with zygomorphic flowers? a) Mustard b) Datura c) Pea d) Chilli
An inferior ovary is characteristic of which type of flower? a) Hypogynous b) Perigynous c) Epigynous d) Protogynous
When the margins of sepals or petals overlap one another but not in any particular direction, the aestivation is called: a) Valvate b) Twisted c) Vexillary d) Imbricate
Stamens united into more than two bundles are described as: a) Monoadelphous b) Diadelphous c) Polyadelphous d) Polyandrous
The arrangement of ovules on a central axis in a multilocular ovary, as seen in tomato, is called: a) Parietal placentation b) Free central placentation c) Axile placentation d) Basal placentation
A fruit that develops from a monocarpellary superior ovary and is one-seeded, like a coconut, is known as a: a) Berry b) Capsule c) Drupe d) Legume
A seed that has endosperm in its mature state is called: a) Non-endospermous b) Apomictic c) Endospermic d) Perispermic
In a monocot seed, the plumule and radicle are enclosed in sheaths called: a) Scutellum and Aleurone b) Coleoptile and Coleorhiza c) Testa and Tegmen d) Epicotyl and Hypocotyl
The symbol ‘G’ with a line below it (G) in a floral formula represents: a) Fused gynoecium b) Inferior ovary c) Superior ovary d) Apocarpous gynoecium
Which of these plants does NOT belong to the Solanaceae family? a) Tomato b) Potato c) Pea d) Brinjal
In the family Solanaceae, the placentation is: a) Marginal b) Axile c) Basal d) Parietal
The protective covering of the root apex is the: a) Coleorhiza b) Root hair c) Root cap d) Pericycle
A sterile stamen is known as a: a) Pistillode b) Staminode c) Antherode d) Filament
In vexillary aestivation, the two smallest anterior petals are termed the: a) Standard b) Wings c) Keel d) Bracts
The part of the leaf that may become swollen to form a pulvinus in leguminous plants is the: a) Lamina b) Petiole c) Stipule d) Leaf base

Essay Questions

Describe the three main types of root systems found in flowering plants, providing examples for each. What are the primary functions that all root systems share?
Illustrate the different regions of a root tip, explaining the cellular activities and functions specific to each zone.
Explain the concept of phyllotaxy. Describe the three main types of leaf arrangement with labeled diagrams and examples for each type.
Compare and contrast racemose and cymose inflorescences. Discuss how the pattern of flower arrangement and axis growth differs between them.
What is a flower? Describe the four main whorls of a typical angiosperm flower and distinguish between accessory and reproductive organs.
Explain the classification of flowers based on the position of the ovary on the thalamus (hypogynous, perigynous, epigynous). Include the corresponding terms for ovary position (superior, half-inferior, inferior) and provide an example for each type.
Define aestivation and placentation. Describe two types of each, using examples from the text to illustrate your answer.
Describe the structure of a dicotyledonous seed and a monocotyledonous seed. Highlight at least three key differences between them.
Provide a semi-technical description of the family Solanaceae, covering its key vegetative and floral characteristics, its floral formula, and its economic importance.
Trace the developmental path from a flower to a fruit and seed. Explain what parts of the flower develop into the pericarp, the seed, and the seed coat after fertilization.

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Answer Keys

Short-Answer Questions Key

The two primary systems are the root system, which is the underground part, and the shoot system, which is the part above the ground.
Morphology is the study of the external features of an organism. It is important because it is used for classification, understanding plant adaptations, and identifying different plant species.
A tap root system consists of a main primary root that grows deep and gives rise to lateral branches (common in dicots). A fibrous root system consists of a large number of roots originating from the base of the stem, with no single main root (common in monocots).
Adventitious roots are those that arise from any part of the plant other than the radicle. An example is the roots growing from the stems of a banyan tree or Monstera.
The four main functions are absorption of water and minerals, providing anchorage, storing reserve food, and synthesizing plant growth regulators.
The root cap is a thimble-like structure at the apex of the root. Its function is to protect the tender apex of the root as it pushes its way through the soil.
The region of meristematic activity contains small, thin-walled cells that divide repeatedly. This region is responsible for producing new cells for root growth.
A stem is distinguished by the presence of nodes (where leaves arise) and internodes (the sections between nodes). It also bears buds and is generally positively phototropic.
The petiole is the stalk that connects the leaf lamina to the stem. It functions to hold the blade up to the light and allows the leaf blade to flutter in the wind for cooling.
A pulvinus is a swollen leaf base. It is typically found in some leguminous plants.
In reticulate venation, the veinlets form a network or web-like pattern, which is typical of dicots. In parallel venation, the veins run parallel to each other within the lamina, which is characteristic of monocots.
A simple leaf has a single, undivided lamina, though the margin may be incised. A compound leaf has a lamina that is divided into multiple distinct segments called leaflets.
Phyllotaxy is the pattern of arrangement of leaves on a stem. The three main types are alternate (one leaf per node), opposite (two leaves per node), and whorled (more than two leaves per node).
In racemose inflorescence, the main axis continues to grow and flowers are borne laterally. In cymose inflorescence, the main axis terminates in a flower, thus limiting its growth.
An actinomorphic flower has radial symmetry and can be divided into two equal halves along any radial plane. A zygomorphic flower has bilateral symmetry and can be divided into two equal halves in only one specific vertical plane.
A hypogynous flower is one where the gynoecium is at the highest position on the thalamus and all other floral parts are below it. The ovary in such a flower is described as superior.
Aestivation is the mode of arrangement of sepals or petals in the floral bud. The four main types are valvate, twisted, imbricate, and vexillary.
‘Epipetalous’ describes the condition where stamens are attached to the petals. This is seen in plants like brinjal.
An apocarpous gynoecium is composed of one or more carpels that are free from each other (e.g., lotus). A syncarpous gynoecium has two or more carpels that are fused together (e.g., tomato).
Placentation is the arrangement of ovules within the ovary. Two types are marginal placentation (e.g., pea), where ovules are on a ridge on the ventral suture, and axile placentation (e.g., tomato), where ovules are attached to a central axis in a multilocular ovary.
A parthenocarpic fruit is a fruit that is formed and develops without the fertilization of the ovary.
In a mango, the pericarp is differentiated into three layers: an outer thin epicarp (skin), a middle fleshy and edible mesocarp, and an inner stony hard endocarp (the stone).
The two layers of a dicot seed coat are the outer testa and the inner tegmen.
The aleurone layer is a proteinous layer that is the outer covering of the endosperm. It separates the embryo from the endosperm.
A floral formula is a summary representation of a flower’s structure using symbols. It provides information about the flower’s sexuality, symmetry, the number of parts in each whorl (calyx, corolla, androecium, gynoecium), and whether these parts are fused or free.

Multiple-Choice Questions Key

c) Fibrous root system
b) Region of elongation
c) Opposite
c) Palmately compound
d) Basipetal
c) Pea
c) Epigynous
d) Imbricate
c) Polyadelphous
c) Axile placentation
c) Drupe
c) Endospermic
b) Coleoptile and Coleorhiza
c) Superior ovary
c) Pea
b) Axile
c) Root cap
b) Staminode
c) Keel
d) Leaf base

Essay Question Answers

Three Main Root Systems: The three main root systems are the tap root, fibrous root, and adventitious root systems.
- The tap root system, found in most dicots like mustard, originates from the radicle of the embryo, which elongates to form a primary root. This primary root grows vertically deep into the soil and gives off smaller lateral roots (secondary, tertiary).
- The fibrous root system, characteristic of monocots like wheat, arises when the primary root is short-lived. A large number of thin, moderately branching roots grow from the base of the stem, forming a dense mat.
- Adventitious roots are roots that grow from any part of the plant other than the radicle. They can arise from stems or leaves, as seen in grass, Monstera, and the prop roots of a banyan tree.
- Shared Functions: All root systems share the primary functions of absorbing water and minerals from the soil, providing anchorage and support for the plant, storing reserve food materials, and synthesizing plant growth regulators.
Regions of the Root Tip: The root tip is divided into four main regions.
- Root Cap: A thimble-like structure that covers the very tip of the root. Its function is to protect the tender meristematic cells of the apex as the root pushes through abrasive soil particles.
- Region of Meristematic Activity: Located just behind the root cap, this region contains small, thin-walled cells with dense protoplasm that are actively dividing (undergoing mitosis). This zone produces new cells for the root cap and for the region of elongation.
- Region of Elongation: Situated proximal to the meristematic region, the cells here undergo rapid enlargement and elongation. This growth is the primary driver of the increase in the root’s length.
- Region of Maturation: Located behind the region of elongation, this is where the elongated cells differentiate and mature into specialized tissues. The most notable feature is the formation of fine, delicate root hairs from epidermal cells, which vastly increase the surface area for water and mineral absorption.
Phyllotaxy: Phyllotaxy is the pattern of arrangement of leaves on a stem or a branch. This arrangement is typically one of three types, optimizing leaf exposure to sunlight.
- Alternate: In this type, a single leaf arises at each node in an alternating pattern up the stem. Examples include china rose, mustard, and sun flower. (A simple diagram would show a stem with single leaves at different levels on opposite sides).
- Opposite: Here, a pair of leaves arises at each node, situated directly opposite each other. Examples include Calotropis and guava. (A simple diagram would show a stem with pairs of leaves at each node).
- Whorled: In this arrangement, more than two leaves arise from a single node, forming a circle or whorl around the stem. An example is Alstonia. (A simple diagram would show a stem with circles of three or more leaves at the nodes).
Racemose vs. Cymose Inflorescence:
- An inflorescence is the arrangement of flowers on the floral axis. In a racemose inflorescence, the main axis has indeterminate growth; it continues to grow and does not terminate in a flower. The flowers are borne laterally on the axis in an acropetal succession, meaning the oldest flowers are at the base of the axis and the youngest flowers and buds are at the apex.
- In a cymose inflorescence, the main axis has determinate growth; it terminates in a flower, which stops its further elongation. Subsequent flowers develop from lateral buds below the terminal flower. This results in a basipetal order of arrangement, where the oldest flower is at the apex (or center) and the younger flowers develop towards the base.
Parts of a Typical Flower: A flower is a modified shoot that serves as the reproductive unit of an angiosperm. A typical flower is composed of four distinct whorls of floral appendages attached to the thalamus.
- Accessory Organs: These are the non-reproductive parts that primarily serve to protect the flower or attract pollinators.
  1. Calyx: The outermost whorl, consisting of units called sepals. They are typically green and leaf-like, protecting the flower in its bud stage.
  2. Corolla: The whorl inside the calyx, consisting of units called petals. Petals are often brightly colored and scented to attract insects for pollination.
- Reproductive Organs: These are the essential parts directly involved in sexual reproduction. 3. Androecium: The male reproductive whorl, composed of stamens. Each stamen has a filament (stalk) and an anther, which produces pollen grains. 4. Gynoecium: The female reproductive whorl, located at the center of the flower. It is composed of one or more carpels. Each carpel has three parts: the ovary at the base (containing ovules), the style (a stalk), and the stigma (the receptive tip for pollen).
Flower Classification by Ovary Position:
- Hypogynous: In this type, the gynoecium occupies the highest position on the thalamus, while the calyx, corolla, and androecium are inserted below it. The ovary is therefore termed superior. Examples include mustard, china rose, and brinjal.
- Perigynous: In this arrangement, the gynoecium is situated in the center, and the other floral parts are located on the rim of the thalamus, which is often cup-shaped. The floral parts are at almost the same level as the ovary. The ovary is described as half-inferior. Examples include plum, rose, and peach.
- Epigynous: Here, the margin of the thalamus grows upward, completely enclosing the ovary and fusing with its wall. The other floral parts (sepals, petals, stamens) appear to arise from the top of the ovary. The ovary is thus termed inferior. Examples include guava, cucumber, and the ray florets of sunflower.
Aestivation and Placentation:
- Aestivation is the mode of arrangement of sepals or petals in a floral bud with respect to other members of the same whorl. Two types are:
  1. Valvate: The margins of the petals or sepals in a whorl just touch one another without any overlapping. An example is Calotropis.
  2. Twisted: The margin of one appendage overlaps the margin of the adjacent one in a regular, directional manner, as seen in china rose and cotton.
- Placentation is the arrangement of ovules within the ovary. Two types are:
  1. Parietal: The ovules develop on the inner wall of the ovary or on the peripheral part. The ovary is typically one-chambered, although it may become two-chambered due to a false septum. Examples are mustard and Argemone.
  2. Basal: The placenta develops at the base of the ovary, and a single ovule is attached to it. Examples are sunflower and marigold.
Dicot vs. Monocot Seed Structure:
- A dicotyledonous seed (e.g., gram, pea) is characterized by having an embryo with two cotyledons. Its outermost covering is a seed coat, differentiated into an outer testa and inner tegmen. The embryo consists of an embryonal axis with a radicle and a plumule, and two often fleshy cotyledons that store food. In many dicots like pea, the endosperm is absent in the mature seed (non-endospermic).
- A monocotyledonous seed (e.g., maize, wheat) has an embryo with only one cotyledon. The seed coat is typically membranous and fused with the fruit wall (pericarp). The seed is usually endospermic, meaning it has a bulky endosperm that stores food. The single, shield-shaped cotyledon is called the scutellum, and the plumule and radicle are protected by sheaths called the coleoptile and coleorhiza, respectively.
- Key Differences: (1) Number of cotyledons (two in dicots, one in monocots). (2) Presence of endosperm (often absent in mature dicots, present in most monocots). (3) Protective sheaths (coleoptile and coleorhiza are present in monocots, absent in dicots).
Description of Family Solanaceae:
- Vegetative Characters: Members are mostly herbs or shrubs. Stems are typically herbaceous, aerial, and branched. Leaves are alternate, simple, and have reticulate venation. An underground stem is found in the potato.
- Floral Characters: The inflorescence is often solitary or cymose. The flowers are bisexual and actinomorphic (radially symmetrical). The calyx has five united sepals (gamosepalous) with valvate aestivation. The corolla has five united petals (gamopetalous) with valvate aestivation. The androecium consists of five stamens that are epipetalous (attached to the petals). The gynoecium is bicarpellary, syncarpous (fused carpels), with a superior, bilocular ovary and axile placentation. The fruit is a berry or capsule.
- Floral Formula: ⊕ ♀ K(5) C(5) A5 G(2) (with an arc showing adhesion between C and A).
- Economic Importance: This family is of great economic importance, providing food (potato, tomato, brinjal), spices (chilli), medicines (belladonna), fumigatories (tobacco), and ornamental plants (petunia).
Development from Flower to Fruit and Seed: After successful pollination, fertilization occurs within the ovule. This triggers a series of developmental changes in the flower. The ovary begins to grow and matures into the fruit. The wall of the ovary develops into the pericarp, or fruit wall. Simultaneously, the ovules contained within the ovary develop into seeds. The integuments of the ovule develop into the seed coat (testa and tegmen). The fertilized egg inside the ovule develops into the embryo, and the primary endosperm nucleus develops into the endosperm, which serves as a nutritive tissue. Other floral parts, such as the sepals, petals, stamens, style, and stigma, typically wither and fall off, though in some cases, parts like the calyx may persist (e.g., in brinjal).

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Glossary of Key Terms

Acropetal: An arrangement where the youngest elements are at the apex and the oldest are at the base.
Actinomorphic: A flower with radial symmetry; can be divided into two equal halves in any radial plane.
Adventitious Root: A root that arises from a plant part other than the radicle.
Aestivation: The mode of arrangement of sepals or petals in a floral bud.
Aleurone Layer: The proteinaceous outer layer of the endosperm in monocot seeds.
Androecium: The male reproductive whorl of a flower, consisting of stamens.
Angiosperms: Flowering plants.
Anther: The part of a stamen that contains the pollen.
Apocarpous: A gynoecium with two or more free (unfused) carpels.
Axile Placentation: Placentation where ovules are attached to a central axis in a multilocular ovary.
Axillary Bud: A bud located in the axil of a leaf.
Basal Placentation: Placentation where the placenta is at the base of the ovary with a single attached ovule.
Basipetal: An arrangement where the oldest elements are at the apex and the youngest are at the base.
Bract: A reduced leaf found at the base of a pedicel.
Calyx: The outermost whorl of a flower, composed of sepals.
Carpel: The female reproductive organ of a flower, consisting of an ovary, style, and stigma.
Coleoptile: The protective sheath covering the plumule in a monocot embryo.
Coleorhiza: The protective sheath covering the radicle in a monocot embryo.
Corolla: The whorl of a flower inside the calyx, composed of petals.
Cotyledon: An embryonic leaf in seed-bearing plants, one or more of which are the first leaves to appear from a germinating seed.
Cymose: A type of inflorescence with determinate growth where the main axis ends in a flower.
Diadelphous: Condition where stamens are united into two bundles.
Dicotyledonous: A plant with two cotyledons in its embryo.
Drupe: A fleshy fruit with a thin skin and a central stone containing the seed.
Embryo: The part of a seed that develops into a plant, consisting of the plumule, radicle, and cotyledons.
Endocarp: The inner layer of the pericarp.
Endosperm: The nutritive tissue in the seeds of most flowering plants.
Epicarp: The outer layer of the pericarp.
Epigynous: A flower where floral parts are attached above the ovary, resulting in an inferior ovary.
Epipetalous: Stamens that are attached to the petals.
Fibrous Root: A root system common in monocots where the primary root is replaced by many thin roots arising from the stem base.
Filament: The stalk of a stamen.
Floral Formula: A symbolic representation of the structure of a flower.
Free Central Placentation: Placentation where ovules are borne on a central axis without any septa.
Fruit: A mature, ripened ovary of a flowering plant, enclosing the seed or seeds.
Gamopetalous: Petals are united or fused.
Gamosepalous: Sepals are united or fused.
Gynoecium: The female reproductive whorl of a flower, consisting of one or more carpels.
Hilum: A scar on a seed coat marking the point of attachment to the fruit stalk.
Hypogynous: A flower where floral parts are attached below the ovary, resulting in a superior ovary.
Imbricate: A type of aestivation where margins of sepals or petals overlap without a specific direction.
Inflorescence: The arrangement of flowers on a floral axis.
Internode: The part of a plant stem between two nodes.
Lamina: The blade or expanded part of a leaf.
Marginal Placentation: Placentation where ovules are arranged along the margin of the ventral suture of the ovary.
Meristematic: Relating to plant tissue consisting of actively dividing cells.
Mesocarp: The middle layer of the pericarp.
Micropyle: A small opening in the surface of an ovule, through which the pollen tube may enter, and which is visible on a seed.
Midrib: The central, prominent vein of a leaf.
Monoadelphous: Condition where stamens are united into a single bundle.
Monocotyledonous: A plant with a single cotyledon in its embryo.
Morphology: The study of the form and structure of organisms.
Node: A point on the stem where a leaf is attached or has been attached.
Ovary: The hollow base of the carpel of a flower, containing one or more ovules.
Ovule: The structure that develops into a seed after fertilization.
Palmately Compound: A compound leaf with leaflets radiating from a single point at the end of the petiole.
Parallel Venation: A vein arrangement in a leaf where veins run parallel to each other.
Parietal Placentation: Placentation where ovules are attached to the inner wall of the ovary.
Parthenocarpic: A fruit developed without fertilization.
Pedicel: The stalk of a single flower.
Perianth: The outer part of a flower, consisting of the calyx and corolla, especially when they are indistinguishable.
Pericarp: The wall of a fruit.
Perigynous: A flower where floral parts are attached around the ovary, on the rim of the thalamus, resulting in a half-inferior ovary.
Petal: A member of the corolla whorl, typically colored.
Petiole: The stalk that joins a leaf to a stem.
Phyllotaxy: The arrangement of leaves on a plant stem.
Pinnately Compound: A compound leaf with leaflets arranged on either side of the rachis.
Placenta: The cushion-like tissue inside the ovary where the ovules are attached.
Placentation: The arrangement of ovules within the ovary.
Plumule: The embryonic shoot in a seed.
Polyadelphous: Condition where stamens are united into more than two bundles.
Polyandrous: Stamens are free, not united.
Polypetalous: Petals are free, not united.
Polysepalous: Sepals are free, not united.
Pulvinus: A swollen leaf base.
Racemose: A type of inflorescence with indeterminate growth, with flowers in acropetal succession.
Rachis: The main axis of a pinnately compound leaf.
Radicle: The embryonic root in a seed.
Receptacle: See Thalamus.
Reticulate Venation: A vein arrangement in a leaf with a net-like pattern.
Root Cap: A cone of cells at the tip of a plant root that protects the apical meristem.
Scutellum: The single, large cotyledon of a monocot embryo, specialized for absorbing nutrients.
Sepal: A member of the calyx whorl, typically green.
Stamen: The male fertilizing organ of a flower, typically consisting of an anther and a filament.
Staminode: A sterile or rudimentary stamen.
Stigma: The receptive tip of a carpel, which is responsible for receiving pollen.
Stipules: A pair of leaf-like appendages at the base of the leaf stalk in some plants.
Style: The stalk connecting the stigma to the ovary in a carpel.
Syncarpous: A gynoecium with two or more fused carpels.
Tap Root: A straight tapering root growing vertically downward and forming the center from which subsidiary rootlets spring.
Tegmen: The inner layer of the seed coat.
Testa: The outer layer of the seed coat.
Thalamus: The swollen part of a flower stalk to which the floral organs are attached.
Twisted: A type of aestivation where one margin of each petal or sepal overlaps the adjacent one.
Valvate: A type of aestivation where the margins of sepals or petals meet at the edges without overlapping.
Venation: The arrangement of veins in a leaf.
Vexillary: A type of aestivation, typical of the pea family, where a large posterior petal overlaps two lateral petals, which in turn overlap two anterior petals.
Zygomorphic: A flower with bilateral symmetry; can be divided into two similar halves in only one plane.