Morphology of flowering plants is an important chapter covered in NCERT biology class 11 syllabus as it enriches the learners with the essential features of flowering plants. Flowering and blossoming plants can instantly beautiful any natural environment with their vibrant colours and fragrances. But do you know there are plants without flowers too? Flowering plants are called angiosperms. If you have ever observed various plant parts, you’ll know that most plants have similar parts such as roots, stems, and leaves. Let’s learn more about the morphology of flowering plants through this blog.
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The root is a part of the plant that anchors it in the soil and is found underground. In dicotyledonous plants, there is a primary root with lateral roots arising from it. This is called the taproot system. Monocotyledonous plants have a fibrous root system with multiple roots originating from the base of the stem. In some cases like grass, the root doesn’t arise from the radical but from other parts and are called adventitious roots.
The root system of a plant has multiple functions:
- Absorption of water and minerals from the soil
- Provides anchorage to the plant in the soil
- Produces plant growth regulators
- The roots can be modified to store food
Roots can be modified to perform functions like:
- To store food as seen in the case of carrot, turnip, and the adventitious root of sweet potato
- For support as seen in the hanging prop roots of banyan trees
- Some root modifications, called lateral roots, are also observed in the stems of maize and sugarcane
- In some plants like Rhizophorathe, roots grow vertically upwards, called pneumatophores, that help the plant absorb oxygen for respiration
In our discussion of Morphology of Flowering Plants, the next topic is Stem. The stem is visible above the ground and bears other essential parts like leaves, flowers, fruits, etc. While the root develops from the radicle of the seed, the stem appears from the plumule. It bears nodes where the leaves arise and the portion between the two nodes is called an internode. The stem also bears buds – terminal found at the growing tip of the stem and axillary found laterally. The main functions of the stem include:
- Conducting minerals and water from the roots to the leaves
- Conducting prepared food from the leaves to all parts of the plant
In some plants, the stems are modified to perform other functions. The important ones as per the biology class 11 syllabus are:
- Underground stems of potato, turmeric, and ginger are modified to store food
- Axillary buds of some stems give rise to stem tendrils to help plants like gourds to climb
- In some plants, the axillary buds are modified to form sturdy, woody thorns as seen in citrus plants
- Plants which grow in arid regions, the stem is modified to form a flattened or cylindrical structure to carry out photosynthesis
- In some plants, the stem falls on the ground and gives rise to new plants when the old ones die
The flattened, green extension of the stem is called a leaf. It usually develops from the node on the stem and has a bud at its axil. As per the morphology of flowering plants chapter, the leaf is the ‘kitchen of the plant’ as it performs photosynthesis. A leaf contains three main parts – leaf base, petiole, and lamina.
The leaf is attached to the stem by the leaf base. The lamina of the leaf blade is the flat, expanded portion of the leaf that contains the veins and veinlets. The petiole or the leaf stalk is what connects the leaf lamina to its base on the stem. The prominent middle vein on the leaf lamina is called the midrib and the other smaller veins extend outwards from the midrib. This is a classic sign of dicot plants.
The pattern formed by the veins on the lamina is called venation. In dicot plants, the veins form a network, called reticulate venation. When the veins run parallel to each other in the lamina, it is called parallel venation. The primary function of a leaf is photosynthesis, for which it contains chloroplasts.
Types of Leaves
Studying class 11 chapter morphology of flowering plants, you will learn about different types of leaves. They can be classified into two types – simple and compound. A simple leaf is one in which its entire lamina is complete or if incised, the incisions do not touch the midrib. When these incisions touch the midrib and divide the leaf into leaflets, it is called a compound leaf. Compound leaves are of two types – pinnately compound in which the leaflets are present along a common axis, and a palmately compound leaf in which the leaflets are attached to one common point such as the tip of the petiole.
Another interesting aspect of leaves is their pattern of arrangement on a stem which is called as a phyllotaxy and is of of three types:
- Alternate: One leaf arises from one node in an alternate manner as observed in China rose, mustard, and sunflower plants
- Opposite: A pair of leaves arise from one node and this is seen in Calotropis, guava, etc.
- Whorled: This happens when more than two leaves arise from one node as seen in Astoria
Though the primary function of a leaf is photosynthesis, it can be modified to perform other functions like support, storage, and protection. Some examples include:
- Tendrils are leaves modified for climbing in a pea plant
- The spines in cactus are leaves modified for protection
- Leaves of onion and garlic become fleshy to store food
- Leaves of an insectivorous plant-like Venus flytrap are for protection
According to the chapter on morphology of flowering plants, the flower is the most attractive part of a flowering plant. Known to be the reproductive part of the plant, flowers are actually meant for sexual reproduction.
As per the NCERT biology class 11 syllabus, a flower is made up of:
- Thalamus: The base or receptacle on which the four whorls of the flower are arranged
- Calyx: This is the first whorl of the flower and is made up of sepals. It is small, usually green in colour, and is considered to be an accessory part of the flower. It is responsible for protecting the flower in its bud stage
- Corolla: This is the second layer of the flower and comprises petals. When the calyx and corolla layers are not distinct from each other, it is called a perianth
- Androecium: The male reproductive organ of the plant that consists of stamens and anthers. The anthers contain pollen grains, which have the male gamete
- Gynoecium: The female reproductive part of the plant is made up of stigma, style, and ovary. The ovary contains ovules, which have the female gamete
Based on symmetry, flowers can be classified as actinomorphic (shows radial symmetry) and zygomorphic (shows bilateral symmetry). Actinomorphic flowers can be divided into two radial halves. Zygomorphic flowers can be divided into two equal halves only along one particular plane. Flowers can be trimerous, tetramerous or pentamerous based on the number of petals a flower has. Flowers that have bracts are called bracteate and those without are called ebracteate.
Have you ever closely observed a banana, mango, mustard or Gulmohar flower? You will observe that they all have multiple tiny flowers rather than one single flower arising from a shoot. This type of arrangement of flowers is known as an inflorescence. Usually, when the tip of the shoot develops into a flower, it is a solitary one. When there is an arrangement of flowers around a floral axis, it is termed as an inflorescence. Inflorescence can be of two types – racemose or cymose – based on whether the apex gets converted into a flower or continues to grow.
Fruit is a characteristic feature of flowering plants. It is the ripened ovary that forms after fertilisation has occurred. As per class 11 chapter morphology of flowering plants, a fruit that is developed without fertilisation is called a parthenocarpic fruit. Generally, fruits are said to have three layers – the outer epicarp, the middle mesocarp, and the inner epicarp. Fruits like mango and coconut are called drupes, they are single-seeded and develop from monocarpellary superior ovaries. These fruits contain a thin epicarp, a fleshy mesocarp, and a stony-hard endocarp.
When the flower gets fertilised, the ovary becomes the fruit and the ovules become the seeds. A seed consists of a seed coat and an embryo. The embryo consists of a radicle, an embryonal axis, and may contain one or two cotyledons. Based on the number of cotyledons, flowering plants can be classified as monocotyledonous (monocots) or dicotyledonous (dicots).
The outermost covering of the seed is the seed coat, which has two layers – the outer testa and the inner tegmen. The seed also contains a hilum, which is a scar on the seed coat and is reminiscent of where the seeds were attached to the fruit. Above the hilum is a small pore called the micropyle. A dicotyledonous seed contains one embryonal axis and two cotyledons that are fleshy and contain food. In some seeds, double fertilisation results in the formation of an endosperm that is used to store food. The image mentioned below describes dicotyledonous seeds as per the morphology of flowering plants.
Most monocotyledonous seeds are endospermic but some are non-endospermic. In seeds of cereals like maize, the seed coat is usually fused with the fruit wall and contains a bulky endosperm. The outer covering of the endosperm separates the embryo by a proteinaceous layer called the aleurone layer. The cotyledon consists of a short axis with a radicle and plumule that are covered by protective sheaths called coleorhiza and coleoptile respectively.
Technical Description of a Flowering Plant
Based on the morphology of flowering plants that you have learnt so far as per the NCERT biology class 11, each of these features can be described briefly using a floral formula. The formula can be written using certain symbols. For example:
Br stands for bracteate, K for calyx, C for corolla, P for perianth, A for androecium, G for gynoecium, G for superior ovary, G for inferior ovary, ♂ for male and ♀ for female plants, ⊕ for actinomorphic flower, and % for zygomorphic flower. Fusion is indicated by enclosing the figure in a bracket and adhesion by a line drawn over the symbol for floral plants.
Here are some practice questions to prepare for the chapter on morphology of flowering plants:
Q.1 When is a flower called zygomorphic or actinomorphic?
A flower is called a zygomorphic when it can be cut into two equal halves only along one vertical plane. However, when a flower can be split into two halves along any radial plane, it is called an actinomorphic flower.
Q2. Give examples of modification of stem.
Some stem modifications include:
- Storage: In some plants like potato, turmeric, and ginger, the stem of the plant gets modified to store food to help the plant in unfavourable conditions
- Stems that help plants climb: Some plants have tendrils that are modified stems to help the plants climb
- Thorns: These are modified leaves found in plants like cacti to protect the plant from harmful predators
Q3. Enlist the parts of a flower with their function
A plant consists of the following parts:
- Receptacle or thalamus: It acts as a base for the whorls of the flower
- Calyx: This is the first whorl of the flower and is made up of sepals. It protects the flower in its bud stage.
- Corolla: This is the colourful petal layer that is responsible for attracting the pollinators
- Androecium: It is made up of stamens and anthers that contain the pollen grains. The pollen grains contain male gametes.
- Gynoecium: It consists of the style, stigma, and ovary. The ovary contains ovules, which house the female gamete.
Q4. Name a plant that has prop roots and one that has lateral roots.
The banyan tree has roots that develop from its branches and provide additional support to the tree. These are called prop roots. Lateral roots are found in maize and sugarcane.
Q5. How is a fibrous root system different from a tap root system?
In the case of a taproot system, there is a primary root with lateral roots arising from it. However, in the case of a fibrous root system, all the roots arise from the base of the stem.
Thus, we hope that through these detailed notes about the morphology of flowering plants, you are now familiar with the essential concepts covered in this chapter. Unsure about finding the right career path? Get in touch with our career experts at Leverage Edu and we will help you explore the best course and university as per your interests and aspirations to ensure that you take an informed decision towards a rewarding career!