Structure of a flowering plant and functions of the various parts of the plant

This article deals with the external morphology of a flowering plant. This article gave an account of different parts of the root system and shoot system of a flowering plant body. Vegetative parts of the plant body like roots, stem, leaves, buds, and the reproductive parts of the plant like flowers, fruits, seeds, and their functions were also discussed in this article. Some frequently asked questions were also provided along with this article.

Structure of a Plant

A flowering plant in its structure includes two main organ systems in it- Root system and Shoot system. These two main organ systems include various organs in them and these different organs work together for the proper functioning of the plant body. A plant body in its structure include vegetative organs and reproductive organs. Roots, stem, leaves, buds are vegetative organs and they help in vegetative growth of the plant body. Flowers are known as the reproductive organ of the plant which helps in the formation of fruits and seeds. The seeds help in the propagation of the plant and thus help in the continuation of the race.
Parts of a Flowering Plant

Morphology of a Flowering Plant (Diagram by the Author)

1. Root system

It is the subterranean or underground part of a plant body. The main root usually develops from the radicle part of the embryo of the seed and the lateral roots develop as branches from the main root. Roots do not possess any chlorophyll and even do not possess any appendages like buds, thorns, leaves, and flowers like the shoot system. The main root shows a positively geotropic or negatively phototropic nature in its growth while the lateral roots are plagiotropic in nature i.e. grow lateral to the vertical direction of the main root. Every root is covered and protected by a root cap. Just above the root cap region, a large number of single-celled root hairs are present in tufts. They will increase the area of water absorption of a plant. Root systems found in plants are of two kinds- Tap root system and Fibrous root system.

1. Taproot system: This type of root system can be found in Dicotyledons plants as the bean, rose, potato, etc. In this type of root system, there is a primary root or mother root developed from the radicle of the embryo. On this bulky mother root somewhat thinner secondary lateral roots and on them still thinner tertiary roots are present. On the tertiary roots and just above the root cap of the mother root an indefinite number of unicellular root hairs will be found in tufts. The roots developed on a plant body other than the mother root are known as adventitious roots. So, secondary roots, tertiary roots, and root hairs of a tap root system come under adventitious roots.

2. Fibrous root system: This type of root system can be found in monocotyledon plants like rice, wheat, maize, etc. In this type of root system, a tuft of thin roots of equal dimension arises from the base of the stem. These roots are known as fibrous roots and the root system formed by them is known as the fibrous root system. There is no mother root in this type of root system as the mother root developed from the radicle degenerate in the initial stage itself and the fibrous roots develop from the base of the stem. As the origin of the fibrous roots is not like the origin of the mother root and hence we can call these roots also as adventitious roots.

Function of the roots

We can attribute the following function to roots in a plant body-

Root fix the plant body firmly to the soil and thus provide firm anchorage to the plant
Roots help to absorb water and minerals from the soil in order to supply it to all parts of the plant body
In some plants, roots help to store food temporarily for the future use of the plant. Ex: Roots in carrot and radish plants

2. Shoot system

The part of the plant which grows above the surface of the soil aerially is known as the shoot system. The shoot system develops from the plumule part of an embryo of the seed. It shows positively phototropic and negatively geotropic nature in its growth.

A shoot system will bear all the aerially grown parts on its body. It includes the main axis or main stem, lateral branches, nodes, internodes, leaves, buds, flowers, fruits as well as other additional appendages like thorns, prickles, tendrils, hairs present on the surface of the stem and leaves, etc.

Stem

The Plumule part of the embryo of the seed develops into the stem or main axis of the plant body. On this main axis, distinct regions called nodes and internodes are present. Node is the region of the stem where a leaf arises. The distance between two nodes is known as internode. In a young plant, the internodes will be very short but as the plants grow in size internodal lengths become increased. The stem is the structure that bears all vegetative and reproductive parts on it. The stem is the structure that carries water and minerals from roots to all parts of the plant body. Young stem containing chlorophyll also carry photosynthesis to a little extent. In some plants like potatoes, Kohlrabi etc. stems store food materials temporarily for future use.

Functions of the stem

The stem bears the aerial parts of the plant like leaves, buds, branches, flowers, and fruits on it
Stem help to expose the leaves properly to Sunlight to carry out photosynthesis for the preparation of food to the plant.
Stem helps to conduct water as well as minerals from roots to the leaves and also other parts of the plant
The stem also helps to conduct prepared food from leaves to the roots of the plant as well as other parts of the plant

Leaf

The leaf is a highly flattened, well-expanded chlorophyll-containing part concerned with photosynthesis. The well-expanded part of the leaf is known as leaf lamina or leaf blade. A small scale-like structure present at the base of a leaf and which protects the leaf in bud condition is known as stipule. The leaf is attached to the stem at the place of a node by means of a stalk-like structure called the petiole. A leaf is a chief organ of photosynthesis in a plant. If a leaf is attached to the stem to the node with the help of a petiole, it is known as a petiolated leaf and if the leaf is directly attached to the stem it is known as a sessile leaf.

Functions of leaf

A most important function of the leaf is to prepare food for the plant through photosynthesis.
Through the small pores present on their surface leaves help in the exchange of gases.
Through the transpiration, process leaves get rid off excess water from the plant body.
In some plants, leaves store food materials in them as in cabbage.
In some plants, leaves carry out vegetative reproduction as in Bryophyllum and Begonia.

Buds

There are two kinds of buds in a plant body- Terminal buds and Axillary buds. Terminal buds are present usually at the tip of the main stem or at the tip of a lateral branch. They are generally surrounded by a rosette of young leaves. An axillary bud will arise in the axil (angle present between the main axis and its leaf) of a leaf. Buds contain young and active meristematic tissue in them. Hence, buds help in the active growth of the plant body. Terminal buds in a plant body will help in the lengthwise growth of the plant body. The axillary bud by its activity will help to develop a new branch from the axil of a leaf. Thus terminal buds and axillary buds will help in the vegetative growth of the plant body. Some times these buds during vegetative growth may transform into thorns or tendrils to provide additional support to the plant. After the vegetative phase of the plant is over, these buds may transform into flowers and help in reproduction.

Flower

After the vegetative phase is over, the terminal buds and axillary buds will transform into floral buds to form flowers. The flower is a reproductive organ of the plant. A flower is a kind of modified shoot where the parts of the shoot are transformed into various parts of the flower. A small scale-like structure that arises just below a flower is known as bract. A bract will protect the flower in bud condition. A flower includes two non-essential whorls calyx, corolla, and two essential whorls androecium, gynoecium. After pollination and fertilization process a flower transform into a fruit enclosing seeds in it. In some plants, a plant may show an aggregation of flowers called Inflorescence at the terminal axis of the shoot.

Fruit

The fruit is a structure formed from the flower of a plant through the steps of pollination and fertilization. After these two steps, the ovary of the flower transforms into fruit whereas the ovules of the ovary transform into seeds of the fruit. Seeds are the reproductive parts of the fruit which include the future miniature plant in the form of the embryo in them. Seeds after their proper dispersal will help in the propagation of the plant.

Most frequently asked questions:-

Mention the vegetaive parts of a plant body.
Ans. Roots, stem, buds, leaves are known to be vegetative parts of the plant body.
What is the role of buds in a flower.
Ans. Axillary buds may transform into new branches in the vegetative phase of the plant body. Axillary or terminal buds may transform into flowers in the reproductive phase of the plant body. In some plants, the buds may transform into thorns or tendrils.
Name the two steps required for a flower to transform into a fruit.
Ans. Pollination and fertilization are the steps required for a flower to transform into a fruit.
Define a node.
Ans. A node is a place on the stem where a leaf arises.
Name two essential organs of a flower.
Ans. Androecium and gynoecium.
Define an Inflorescence.
Ans. An inflorescence is an aggregation of flowers on a common axis.
Name the reproductive organ of a plant.
Ans. Flower
What are adventitious roots.
Ans. Roots developed from any part of the plant body other than taproot are known as adventitious roots.
Name the type of root system found in Groundnut and Rice plant.
Ans. We can find the taproot system in the groundnut and a fibrous root system in rice plants.
Name two important life activities carried out by leaves of a plant.
Ans. Photosynthesis and Transpiration.