Root,Root System,Aerating Roots: Pneumatophores,Root Modifications,For Special Functions
Root
Morphology of Flowering Plants
• Morphology is the name given to the science that deals with the study of the
form and structure of things. No matter which plant you take, the morphology
of a flowering plant includes the roots, stem, leaves, flowers, and fruits.
Flowering Plants
• Flowering plants are the most diverse group of land plants with 300,000
known species.
• These are also known as angiosperms and produce seed-bearing fruits.
• It is believed that the flowering plant evolved from gymnosperms during
the Triassic period and the first flowering plant emerged 140 million years
ago.
• Flowers are the reproductive organs of the flowering plants and the most
important feature that distinguishes them from other seed plants.
• The flowering plants reproduce by the process of pollination. In this, the
pollen grains transfer from the anther of the male flowers to the stigma of the
female flower where fertilization occurs and seed is formed.
• A plant has two systems: Root system and Shoot system.
• The underground part is called the root while the one above is named the
shoot.
Morphology of Flowering Plants
Root System
• The root is a brown, non-green and underground part of a plant.
• Root with their branches is collectively called a Root system.
• There are three types of the root system:
| Root System | ||
|---|---|---|
| Taproot System | Fibrous root System | The Adventitious root System |
| Mainly found in Dicotyledonous plants. | Mainly found in ferns and in all monocotyledonous plants. | The roots which originate from any part of the plant body other than the radicle is called the adventitious root system |
| It develops from the radicle of the germinating seed, along with its primary roots and branches, giving rise to the taproot system. | This root develops from thin, moderately branching roots or primary roots, growing from the stem | mainly found in all monocotyledonous plants.In plants, the adventitious root system is used for various purposes, like mechanical support vegetative propagatioj,etc |
| Mustard seeds, mangoes, grams and banyan. | it usually does not penetrate deep into the soil, therefore, on fuull maturity, these roots look like a mat or a carpet on the floor.Wheat, paddy, grasss, carrots,onion. | Banyan tree, maize, oak trees. |
Functions of Root
• Roots perform various functions that are necessary for the survival of the plants. They
are an integral or integrated system that helps the plant in:
• Anchoring:
plant body, ensuring that it stands erect.
• Absorption:
Primary function of the roots is to absorb water and dissolved minerals
from the soil. This is crucial as it helps in the process of photosynthesis.
• Storage:
Plants prepare food and store in the form of starch in the leaves, shoots and
roots. Prominent examples include carrots, radish, beetroot, etc.
• Reproduction:
Even though roots are not the reproductive part of plants, they are
vegetative parts. In some plants, the roots are a means of reproduction. For instance,
new plants arise from creeping horizontal stems called runners (stolons) in jasmine,
grass, etc. This type of reproduction is called vegetative reproduction.
• Ecological Function:
They check soil erosion, provide sustenance and also habitat to
various organisms.
Root Modifications:
Tap root modification
• For Food Storage
• In some plants, the roots become fleshy due to the absorption of food material.
• The aerial parts of these plants are worn out due to unfavourable conditions. When
the conditions are favourable again new buds emerge either from the fleshy root or
from a small bit of stem above.
For eg., the taproots of carrot and turnip get swollen to store food.
• Depending upon their shapes, they are classified as;
• Conical roots:
are broad at the base and conical at the apex, eg., carrot
• Fusiform roots:
are swollen in the middle and tapering towards both the ends, eg.,
radish
• Napiform roots:
are spherical at the base and taper towards the apex, eg., turnip
Aerating Roots: Pneumatophores
For better Respiration
• In some halophytes such as Rhizophora that grow in swampy areas, the
roots emerge out of the ground and grow upwards to get oxygen for
respiration.
• The root tips of these plants have minute pores called lenticels through
Nodulated Roots
• Roots of the leguminous plants are modified into root nodules which
contain nitrogen-fixing bacteria such as Rhizobium.
• They help in fixing the atmospheric nitrogen into nitrates and make it
available to the plant.
Root Modifications
Adventitious root modification
For Food Storage
• Adventitious roots are modified into:
• Simple Tuberous Roots are swollen and do not assume any shape. For eg.,
sweet potato
• Nodulose Roots are single beads. They become swollen at the apex and have a
definite shape, eg., Cucurma amanda or mango ginger. - It is very similar to
common ginger but has a raw mango flavour.
• Fasciculated Tuberous Roots is the cluster of adventitious roots for food
storage. They have a definite shape, eg., Dahlia
• Moniliform Roots are swollen and constricted, eg., grasses
• Annulated Roots has an appearance of discs placed one over the other, eg.,
Ipecac..
• .For Mechanical Support
• Prop Roots:
These roots develop from the branches of the tree, hang downwards, and penetrate into the ground thereby supporting the tree. Eg., roots of the banyan tree.
• Stilt Roots:
These roots grow obliquely from the basal node of the stem. Eg., roots of the sugarcane.
• Climbing Roots:
These roots arise from the app nodes and attach themselves to some support to climb over it. Thus, they provide support to the plant. Eg., Money plant
• Clinging Roots:
These roots enter the crevices of some support and fix the plant. Eg., epiphytes orchids
• Buttress Roots:
These are vertically elongated basal part of the stem which spread in different directions in the soil. These are horizontally compressed and appear like planks. Eg., Bombax.
For Special Functions
• Epiphytic Roots:
These roots are aerial, hanging and spongy. They have a porous wall and absorb moisture from the atmosphere. These aerial roots possess a special sponge-like tissue known as velamen.
• Velamen absorbs and stores moisture from the air since these plants do not have direct contact with the soil.
• Sucking Roots: These are microscopic, developed by the roots to absorb nutrients from the host.
• These are also known as parasitic roots or haustoria because these are found in non-green parasitic plants.
• These roots arise from the nodes and penetrate into the host tissue. They then enter into the conducting tissue from where they obtain the required food material.
• Floating Roots: -
These arise from the nodes of the aquatic plants and help in floating and respiration. Eg., Jussiaea. These roots are very spongy in nature and look like a mass of white cotton. The plant floats due to its buoyancy. They dry when taken out of the water.
For Special Functions
• Assimilatory Roots: These are also known as photosynthetic roots. These, when exposed to the sun, develop chlorophyll and manufacture food.
• Eg., In Tinospora, the roots hang as green threads from the nodes during the rainy season. They assimilate carbon dioxide in the presence of sunlight.
• Mycorrhizal Roots: The symbiotic association of a fungus with higher plants is called mycorrhizal root. The fungus absorbs nutrients from the soil for the plant, and the plant, in turn, provides organic food to it. Eg., Pinus
• Reproductive Roots: In some plants such as sweet potato, the adventitious roots give rise to buds which develop into leafy shoots. Root cuttings are the main mode of reproduction.
Typical Structure of Root
• Typical roots contain three different sections, or zones:
Meristematic zone,
Zone of elongation, and
Zone of differentiation.
In the meristematic zone, named after the apical meristem, the plant cells undergo rapid mitotic division, creating new cells for root growth. These new cells, once they enter the zone of elongation, begin, unsurprisingly, to elongate, furnishing the root with added length.
The zone of differentiation contains mature, specialized cells, such as phloem, xylem, and root hairs.
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