A flowering plant has a recognisable external structure. Its roots, stem and leaves support growth and nutrition, while its flowers, fruits and seeds are involved in reproduction. The study of these visible forms and parts is called morphology.
Class 11 Biology Chapter 5 Morphology of Flowering Plants Notes
In this chapter, you will identify the main parts of a flowering plant, compare common variations and study the characteristic features of the family Solanaceae.
Table of Contents
Main Parts of a Flowering Plant
A flowering plant is commonly described in two systems:
- Root system: usually grows below the ground and anchors the plant.
- Shoot system: includes the stem, branches, leaves, flowers and fruits.
The exact appearance of these parts varies between plant species. Observing those variations helps us identify and classify plants.
The Root
A root generally develops from the radicle of a germinating seed. It anchors the plant and absorbs water and minerals from the soil. Some roots also store food or provide extra support.
Types of Root Systems
Taproot system: The primary root continues to grow and produces smaller lateral roots. It is common in many dicot plants, such as mustard.
Fibrous root system: Many thin roots arise near the base of the stem. This is common in plants such as wheat.
Adventitious roots: Roots arise from a plant part other than the radicle, such as a stem. The banyan tree’s supporting roots are an example.
Regions Near the Root Tip
The root cap protects the growing tip as it moves through soil. Behind it are regions where cells divide, lengthen and mature. Root hairs in the maturation region increase the surface area available for absorption.
Root Modifications
Some roots perform extra functions. For example, a carrot has a food-storing root. Prop roots help support a banyan tree. Roots growing from a maize stem can provide additional support.
Common mistake: A potato is a modified stem, while a sweet potato is a modified root.
The Stem
The stem supports leaves, branches, flowers and fruits. It contains nodes, where leaves arise, and internodes, the regions between nodes. The stem also helps transport materials through the plant.
A stem may be modified for other functions:
- A potato tuber stores food.
- A ginger rhizome is an underground stem.
- Some plants have stem tendrils that help them climb.
- Some stems are modified for protection or photosynthesis.
When identifying a modified structure, look for stem features such as nodes, internodes or buds.
The Leaf
A typical leaf has a leaf base, a petiole and a lamina or blade. Leaves are major sites of photosynthesis. They also exchange gases and lose water through transpiration.
Leaf Venation
Reticulate venation forms a branching network of veins and is common in many dicots.
Parallel venation has veins running roughly alongside one another and is common in many monocots.
These are useful patterns, although identifying a plant should involve more than one feature.
Simple and Compound Leaves
A simple leaf has one blade. The blade may have cuts, but they do not divide it into separate leaflets.
A compound leaf is divided into distinct leaflets. Look for the position of the axillary bud: it occurs at the base of the whole leaf, not at the base of each leaflet.
Leaf Arrangement
Phyllotaxy describes how leaves are arranged on a stem. Common patterns are alternate, opposite and whorled.
Inflorescence
An inflorescence is the arrangement of flowers on a floral axis.
In a racemose inflorescence, the main axis continues to grow, and flowers are generally arranged with older ones towards the base and younger ones towards the tip.
In a cymose inflorescence, the main axis ends in a flower. The older flower is generally at the top or centre, with younger flowers developing below or around it.
Memory aid: Racemose has a continuing main axis; cymose has a main axis that ends in a flower.
The Flower
A flower is the reproductive structure of an angiosperm. A typical flower may contain four kinds of parts arranged in whorls:
- Calyx: sepals, which often protect the flower bud.
- Corolla: petals, which may help attract pollinators.
- Androecium: stamens, the male reproductive parts.
- Gynoecium: carpels, the female reproductive parts.
A stamen usually has a filament and an anther. A carpel has a stigma, style and ovary. Ovules are present inside the ovary.
A flower with both stamens and carpels is bisexual. A flower with only one of these reproductive structures is unisexual.
Symmetry of Flowers
An actinomorphic flower can be divided into similar halves along more than one vertical plane through its centre.
A zygomorphic flower can be divided into similar halves along only one vertical plane.
Position of the Ovary
In a hypogynous flower, the other floral parts arise below the ovary; the ovary is described as superior. The position of an ovary is an important feature when describing a flower family.
Fruit and Seed
After fertilisation, the ovary usually develops into a fruit, while the ovules develop into seeds. A fruit protects the seeds and may help in their dispersal.
A seed contains an embryo. The embryo can develop into a new plant when conditions are suitable. Seeds also contain stored food or tissues that supply nutrients during early growth.
Monocot seeds have one cotyledon; dicot seeds have two cotyledons. Maize and pea are familiar examples, respectively.
Family Solanaceae
Solanaceae includes familiar plants such as tomato, brinjal, potato and Datura. Its members may be herbs, shrubs or small trees.
Features commonly used to describe this family include:
- leaves generally arranged alternately;
- flowers generally bisexual and radially symmetrical;
- five sepals that are joined;
- five petals that are joined;
- five stamens attached to the corolla;
- a superior ovary formed from two joined carpels; and
- fruits commonly developing as berries or capsules.
For example, tomato and brinjal produce berries. When describing any plant family, examine its vegetative parts, flower and fruit together rather than relying on only one feature.
Quick Revision
- Root: anchorage and absorption; may also store food or provide support.
- Stem: bears nodes, internodes, leaves and reproductive structures.
- Leaf: commonly carries out photosynthesis.
- Inflorescence: arrangement of flowers on an axis.
- Flower: reproductive structure containing floral whorls.
- Fruit: usually develops from the ovary after fertilisation.
- Seed: develops from an ovule and contains an embryo.
- Solanaceae: family including tomato, brinjal and potato.
Common Mistakes to Avoid
- Do not call a potato tuber a root; it is a modified stem.
- Do not confuse a leaflet with a complete leaf.
- Do not mix up the development of the fruit and seed: the ovary usually forms the fruit, while an ovule forms a seed.
- Do not identify racemose and cymose inflorescences only by appearance; consider whether the main axis keeps growing.
- Do not describe every flower as bisexual or every ovary as superior.
Check Your Understanding
1. What are nodes and internodes?
Nodes are positions on a stem where leaves arise. Internodes are the regions between successive nodes.
2. What is the difference between taproot and fibrous root systems?
A taproot system has a prominent primary root with branches. A fibrous root system consists of many thin roots arising near the base of the stem.
3. Which plant structure develops into a seed?
An ovule develops into a seed after fertilisation.
4. Name two plants in Solanaceae.
Tomato and brinjal.
5. What is an inflorescence?
It is the arrangement of flowers on a floral axis.
Continue Learning
Return to the CBSE Class 11 Biology – Complete Study Guide to browse the chapters. Continue with Chapter 6: Anatomy of Flowering Plants when its notes are available.
Frequently Asked Questions
What is plant morphology?
It is the study of the external form and structures of plants.
What is the difference between a taproot and a fibrous root system?
A taproot has a prominent primary root; a fibrous system has many similarly sized roots arising near the stem base.
What are adventitious roots?
They are roots that arise from plant parts other than the radicle, such as a stem or leaf.
What are the main functions of a stem?
A stem supports leaves, flowers and fruits and transports water, minerals and food.
What is the difference between a node and an internode?
A node is a point where leaves or branches arise; an internode is the region between two nodes.
What are the main parts of a typical leaf?
Leaf base, petiole and lamina or leaf blade.
What is venation?
Venation is the arrangement of veins and veinlets in the leaf blade.
How is a simple leaf different from a compound leaf?
A simple leaf has an undivided lamina; a compound leaf has distinct leaflets.
What is phyllotaxy?
It is the arrangement of leaves on a stem or branch.
What is an inflorescence?
It is the arrangement of flowers on a floral axis.
What distinguishes racemose from cymose inflorescence?
In racemose inflorescence the main axis continues growing; in cymose it ends in a flower.
What are the four main floral whorls?
Calyx, corolla, androecium and gynoecium.
What is an ovary’s placentation?
Placentation is the arrangement of ovules within an ovary.
What develops into a fruit and a seed?
The ovary usually develops into the fruit, and each fertilised ovule develops into a seed.
Which plant family is described in the current chapter scope?
Solanaceae, the family that includes plants such as tomato, potato and brinjal.