Next upcoming important chapters for NEET are:
- Morphology of flowering plants
- Sexual Reproduction in Flowering Plants
- Molecular Basis of Inheritance
- Principles of Inheritance and Variation
- Biological Classification
Morphology of flowering plants
Morphology refers to the study of the form and structure of living organisms. The morphology of flowering plants includes the study of their various parts, their functions and their relationships with each other. The parts of a flowering plant include the root system and shoot system (the stem, the leaves, the flowers, the fruits and seeds). Each of these parts has a specific morphology that contributes to the overall function of the plant.
If you pull out any weed you will see that all of them have roots, stems
and leaves. They may be bearing flowers and fruits. The underground
part of the flowering plant is the root system while the portion above the
ground forms the shoot system.
Stem:
The stem of a flowering plant provides support for the plant and serves as a conduit for water and nutrients to move from the roots to the leaves. The stem can be divided into several sections, including the nodes, internodes, and buds.
Leaves:
Leaves are the main photosynthetic organs of a flowering plant. They are responsible for producing food for the plant through the process of photosynthesis. Leaves can be classified into two main types: simple leaves and compound leaves. Simple leaves have a single blade, while compound leaves have multiple leaflets.
Flowers:
Flowers are the reproductive structures of a flowering plant. They are responsible for producing seeds, which can grow into new plants. Flowers can have a wide range of morphological characteristics, including the number of petals, the arrangement of the petals, and the shape of the reproductive structures.
Fruits:
Fruits are the mature ovaries of a flowering plant. They contain seeds and are responsible for protecting and dispersing the seeds. Fruits can have a wide range of morphological characteristics, including their shape, size, and texture.
Understanding the morphology of flowering plants is important for a variety of reasons, including plant identification, plant breeding, and understanding the ecological roles of plants in their natural environments.
We can discuss each morphological character in detail.
Root
The roots are Ortho geotropic (Move towards gravity) and Apo phototrophic (Move away from the sun light) in nature. The main functions of roots are 1) absorbing water and nutrients from the soil, 2) Anchorage, 3) storage of food, 4) synthesis of Plant growth regulators (PGRs).
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The roots which can directly arise from radicle are called Primary roots. Taproots have a single main root that grows deep into the soil, while fibrous roots have many small roots that spread out close to the soil surface. The root system can be divided into two main types:
1) Taproot system
2) Adventitious root system
1) Taproot System:
- The taproot is usually formed from the radicle of the seed, which is the first structure to emerge from the seed during germination.
- The taproot is thick and fleshy and serves as a storehouse for food.
- The taproot system is common in dicotyledonous plants. Ex: Carrot, Beetroot and Dandelion, Mustard.
- The primary roots and its branches constitute the tap root system.
2) Adventitious root System:
- Roots arise from any part of the plant except radicle. These are again divided into fibrous roots and foliar roots.
- Fibrous roots are many small roots that arise from the base of the stem, that can grow close to the soil surface. The fibrous roots are thin and spread out in all directions.
- The fibrous root system is common in monocotyledonous plants such as grasses, wheat and rice.
- Foliar roots arise from leaves (Ex: Bryophyllum, Bignonia).
In dicots primary roots are long lived but in monocots primary roots are short lived (Ephemeral) and replaced with fibrous roots.
Root modifications:
1. Storage roots
2. Adventitious roots
3.Prop roots
4. Pneumatophores
5. Contractile roots
- Storage Roots: Some plants have roots that are modified to store food. Examples include carrots, sweet potatoes, radish and turnips.
- Adventitious Roots:Adventitious roots can grow from a part of the plant other than the radicle, such as stem or leaves. These roots can help anchor the plant in the soil or provide additional support. Examples of plants with adventitious roots include Asparagus, ivy and corn.
- Prop Roots:Prop roots are modified roots that grow from the stem and help support the plant. Eg: banyan trees and corn.
- Pneumatophores:Pneumatophores are modified roots that grow above the ground in swampy areas. They help the plant obtain oxygen from the air. Eg: mangroves and cypress trees.
- Stilt roots: These roots develop from the lower nodes of the stem and give additional support to plants. Eg: Maize and Sugarcane.
- Nodular roots: In Fabaceae members, roots having nodules called as nodular roots. nodular roots possess symbiotic bacteria Rhizobium helps in nitrogen fixation. Eg: Groundnut and Beans.
Regions of the Root: The root of a plant is divided into different regions that serve different functions. The main regions of the root are:
1) Root cap
2) Meristematic region
3) Elongation region
4) Maturation region
5) Root hairs
1) Root Cap: The root cap is a protective structure at the tip of the root that covers the apical meristem, which is responsible for the growth of the root. The root cap secretes a lubricating substance that helps the root push through the soil as it grows.
2) Meristematic Region: The meristematic region is the area of the root where cell division occurs. This region is responsible for the growth of the root, and it is located just behind the root cap.
3) Elongation Region: The elongation region is the area of the root where cells become longer and the root begins to grow in length. This region is located behind the meristematic region and is responsible for the primary growth of the root.
4) Maturation Region: The maturation region is the area of the root where cells differentiate into specific cell types, such as parenchyma, collenchyma, and sclerenchyma cells. This region is located behind the elongation region and is responsible for the secondary growth of the root.
5) Root Hairs: Root hairs are small, finger-like projections that extend from the epidermal cells of the root. They increase the surface area of the root, allowing it to absorb water and nutrients more efficiently.
Understanding the different regions of the root is important for understanding the growth and development of plants. Different regions of the root are responsible for different functions, and their proper development is crucial for the overall health and vitality of the plant.
Understanding the different regions of the root is important for understanding the growth and development of plants. Different regions of the root are responsible for different functions, and their proper development is crucial for the overall health and vitality of the plant.
The STEM
- The stem is the ascending part of the axis bearing branches, leaves, flowers and fruits.
- It develops from the plumule of the embryo of a germinating seed.
- The stem bears nodes and internodes. The region of the stem where leaves are born are called nodes while internodes are the portions between two nodes.
- The stem bears buds, which may be terminal or axillary.
- It conducts water, minerals and photosynthates. Some stems perform the function of storage of food, support, protection and of vegetative propagation.
Stem modifications:
1) Underground stem modifications:
2) Aerial stem modification:
3) Sub aerial stem modification:
1) Underground stem modifications:
- Underground stem modifications are specialized structures that plants have developed to adapt to various environmental conditions.
- It helps plants to survive in a variety of environments by providing storage for nutrients and water, enabling vegetative propagation, and helping plants to spread and colonize new areas.
a) Rhizomes: These are horizontal underground stems that grow parallel to the soil surface. They have nodes and internodes, from which roots and shoots arise. Ex: Ginger, Turmeric and many grasses, ferns, and some woody plants.
b) Tubers: These are enlarged, fleshy underground stems that store nutrients (food) and water. Eyes show vegetative propagation, Ex: potatoes and yams.
c) Bulbs: These are underground stems (reduced) that are surrounded by fleshy storage leaves called scales. Ex: Onions and lilies.
d) Corms: These are rounded underground stems that grow vertically in a particular depth of the soil, that store nutrients and water. Ex: Colocasia, Amorphophallus (zaminkand), gladiolus and crocus.
2) Aerial stem modification:
a) Stem tendrils: These are thin, coiling structures that arise from stems and help the plant to climb or support itself. Axillary or terminal bud is modified as tendrils.
Ex: From axillary bud: Cucumber, pumpkin, watermelon, From terminal bud: Grapevine.
b) Thorns: These are modified stems that have become hardened and sharp to protect the plant from herbivores. Ex: Bougainvillea, Citrus.
c) Phylloclade: In xerophytes stem is modified into green colored structures for photosynthesis. Ex: Opuntia, Casuarina.
3) Sub aerial stem modification:
a) Runners: Some plants spread to new niches with adventitious roots at nodes. Ex: Grasses, Strawberry, Oxalis
b) Stolon's: It is a slender, aerial lateral branches arising from the base of the main axis and grows obliquely downwards to touch the ground and produce adventitious roots. Ex: Nerium, Jasmine
c) Sucker: Underground branch grows horizontally beneath the soil and come out obliquely upward called sucker. Ex: Chrysanthemum.
d) Offset: A lateral branch with short
internodes and each node bearing a rosette of leaves and a tuft of roots is
found in aquatic plants like Pistia and Eichhornia.
THE LEAF
