Introduction
The flowering plants, also called angiosperms form the most advanced group. They all have enclosed seeds and bear flowers.
In some plants like grasses, the flowers may not be conspicuous.
The flowering plants have been classified into monocots and dicots.
Monocots are more advanced forms and have probably evolved from primitive dicots.
"Plant morphology deals with the study of external form and structure of plants."
All flowering plants have two major systems.
(i) The root system: It is the underground system, usually below the soil and originates from the radicle.
(ii) The shoot system: It is an aerial system, usually above the soil and originates from the plumule. It consists of stem, branches, leaves, flowers, fruits and seeds.
Various parts of the flowering plants are classified into two groups according to their function
(i) Vegetative parts: Roots, stems, branches and leaves
(ii) Reproductive parts: Flowers, fruits and seeds
The Root
The root system of a plant remains inside the soil. The soil provides anchorage, water and minerals.
On germination of a seed, the first root arises from the radicle of the embryo plant and grows downwards. This is called primary root.
In majority of dicotyledonous plants, it is the direct elongation of the radicle.
After a short period of growth, it gives off lateral roots called secondary roots.
Further branching gives rise to tertiary roots.
These roots branch further to form a root system.
The root system provides a large surface area for the absorption of water and mineral salts.
Types of roots
(a) Tap root system: The primary root and its branches constitute the tap root system. It is common in dicots, ex: mustard, carrot, turnip.
(b) Fibrous root system: In monocotyledonous plants, the primary root is short lived and is replaced by a large number of roots that originate from the base of the stem and form the fibrous root system. Ex: maize, paddy,coconut.
(c) Adventitious root system: these are the roots that grow from any part of the plant other than the radicle or the true root ex: grass, monster,banyan tree. These are found in both dicots and monocots.
Functions of roots
Primary functions are performed by the normal roots of almost all plants
1. Anchorage of the plant to the substratum
2. Absorption of water and minerals
3. Conduction of the absorbed water and minerals to the stem
4. Synthesizing plant growth regulators
Secondary functions are performed by certain roots, which are specifically modified
1. Storage of food
2. Provision of additional support
3. Respiration
4. Photosynthesis
5. Reproduction
6. Floating and balancing etc.
Regions of the root
A typical root has five regions.
(i) Root cap region
(ii) Meristematic region
(iii) Region of elongation
(iv) Root hair region
(v) Region of maturation
(i) Root cap: Each root is covered at its apex or tip by a thick cup/thimble-like structure called the root cap.
Root cap protects the delicate apex of the root.
Cells of root cap secrete mucilage, which acts as a lubricant and helps the root to penetrate the hard soil.
If it gets damaged, it is renewed again.
(ii) Meristematic region: Just above the root cap is a small meristematic region, extending for a few millimeters.
The cells of this region consists of meristematic cells that keep dividing repeatedly and give rise to root cap as well as the next upper region
The cells are very small, thin-walled, densely protoplasmic and actively dividing, hence this can also be called as the region of cell division.
(iii) Region of elongation: Just above the meristematic region is the region of elongation.
The cells in this region undergo rapid elongation and enlargement and are responsible for the growth of root in length.
(iv) Root hair region: This region is about 1-6cm in length and lies just above the region of elongation.
These are very fine, delicate, thread-like structures formed from epidermal cells.
The root hairs are very fine, delicate, thread-like, single celled, tubular structure which remain in contact with soil particles.
They are short lived and are replaced by new root hairs after every 10 to 15 days.
They are responsible for absorption of water and minerals.
The root hairs increase the surface area of absorption.
(v) Region of maturation: Next to the region of elongation is the region of maturation.
The cells of this region undergo differentiation/maturation to form primary root tissues like cortex, endodermis, xylem and phloem.
This region helps in fixation of plant body into the soil and also in conduction of absorbed substances.
As the epidermal cells become mature, the root hair shrink and become non-functional.
Modifications of Root
Both tap and adventitious roots undergo modification to perform specialized functions such as storage of food, additional mechanical support or certain vital functions of plant.
Click Here for more details on modifications of root
The flowering plants, also called angiosperms form the most advanced group. They all have enclosed seeds and bear flowers.
In some plants like grasses, the flowers may not be conspicuous.
The flowering plants have been classified into monocots and dicots.
Monocots are more advanced forms and have probably evolved from primitive dicots.
"Plant morphology deals with the study of external form and structure of plants."
(i) The root system: It is the underground system, usually below the soil and originates from the radicle.
(ii) The shoot system: It is an aerial system, usually above the soil and originates from the plumule. It consists of stem, branches, leaves, flowers, fruits and seeds.
Various parts of the flowering plants are classified into two groups according to their function
(i) Vegetative parts: Roots, stems, branches and leaves
(ii) Reproductive parts: Flowers, fruits and seeds
The Root
The root system of a plant remains inside the soil. The soil provides anchorage, water and minerals.
On germination of a seed, the first root arises from the radicle of the embryo plant and grows downwards. This is called primary root.
In majority of dicotyledonous plants, it is the direct elongation of the radicle.
After a short period of growth, it gives off lateral roots called secondary roots.
Further branching gives rise to tertiary roots.
These roots branch further to form a root system.
The root system provides a large surface area for the absorption of water and mineral salts.
Types of roots
(a) Tap root system: The primary root and its branches constitute the tap root system. It is common in dicots, ex: mustard, carrot, turnip.
(b) Fibrous root system: In monocotyledonous plants, the primary root is short lived and is replaced by a large number of roots that originate from the base of the stem and form the fibrous root system. Ex: maize, paddy,coconut.
(c) Adventitious root system: these are the roots that grow from any part of the plant other than the radicle or the true root ex: grass, monster,banyan tree. These are found in both dicots and monocots.
| Tap root system | Fibrous root system |
|---|---|
| Primary root continues to grow and remains distinct. | Primary root stops growing and is not distinct. |
| Primary root develops into tap root and gives off lateral roots that grow outwards and downwards. | Number of similar sized lateral roots develop from the stem base and give rise to a mass of branching fibrous roots. |
| The large main tap root is true root as it develops directly from the radicle. | The radicle does not dominate and its growth stops early in germination. All fibrous roots are adventitious. |
| Tap root may reach very deep in soil. | Roots are usually shallow and spread in a large area rather than depth. |
| Present in most dicots. | Present in most monocots. |
| Ex: Mustard, carrot, turnip, etc. | Ex: Grasses, maize, etc. |
| Tap root or true root | Adventitious root |
|---|---|
| Develops directly from the radicle. | Develops from parts of the plant other than the radicle. |
| Primary root continues growing and is distinct. | Primary root ceases to grow and shrivels up. |
| These are always underground, i.e. below the soil. | May be underground or aerial. |
| Main tap root gives rise to the fine lateral roots. | Forms a cluster of roots which may originate from the same point or area. |
Functions of roots
Primary functions are performed by the normal roots of almost all plants
1. Anchorage of the plant to the substratum
2. Absorption of water and minerals
3. Conduction of the absorbed water and minerals to the stem
4. Synthesizing plant growth regulators
Secondary functions are performed by certain roots, which are specifically modified
1. Storage of food
2. Provision of additional support
3. Respiration
4. Photosynthesis
5. Reproduction
6. Floating and balancing etc.
Regions of the root
A typical root has five regions.
(ii) Meristematic region
(iii) Region of elongation
(iv) Root hair region
(v) Region of maturation
(i) Root cap: Each root is covered at its apex or tip by a thick cup/thimble-like structure called the root cap.
Root cap protects the delicate apex of the root.
Cells of root cap secrete mucilage, which acts as a lubricant and helps the root to penetrate the hard soil.
If it gets damaged, it is renewed again.
(ii) Meristematic region: Just above the root cap is a small meristematic region, extending for a few millimeters.
The cells of this region consists of meristematic cells that keep dividing repeatedly and give rise to root cap as well as the next upper region
The cells are very small, thin-walled, densely protoplasmic and actively dividing, hence this can also be called as the region of cell division.
(iii) Region of elongation: Just above the meristematic region is the region of elongation.
The cells in this region undergo rapid elongation and enlargement and are responsible for the growth of root in length.
(iv) Root hair region: This region is about 1-6cm in length and lies just above the region of elongation.
These are very fine, delicate, thread-like structures formed from epidermal cells.
The root hairs are very fine, delicate, thread-like, single celled, tubular structure which remain in contact with soil particles.
They are short lived and are replaced by new root hairs after every 10 to 15 days.
They are responsible for absorption of water and minerals.
The root hairs increase the surface area of absorption.
(v) Region of maturation: Next to the region of elongation is the region of maturation.
The cells of this region undergo differentiation/maturation to form primary root tissues like cortex, endodermis, xylem and phloem.
This region helps in fixation of plant body into the soil and also in conduction of absorbed substances.
As the epidermal cells become mature, the root hair shrink and become non-functional.
Modifications of Root
Both tap and adventitious roots undergo modification to perform specialized functions such as storage of food, additional mechanical support or certain vital functions of plant.
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