Parts of a Plant: Plant kingdom, Root System, Shoot System, Practice Problems, and FAQs

You all like stories. In our childhood days our parents and grandparents used to narrate stories for us. Let me tell you a short story for you now. Once upon a time a large elephant approached a group of blind guys as they were crossing a road. Though none of them had seen it, they all knew it was an elephant. How was it possible? They all touched the elephant and made a cumulative decision based on the examination in the below mentioned way. 

Each of them went and touched the part they could get their hands on and from what they felt they described the elephant as you see here. The one who touched the trunk said that the elephant is like a snake. The tusk was described as a spear by one. Ears felt like a fan to one. The huge body felt like a giant wall to one. The legs felt like huge tree trunks to someone. The tail was described as a rope. All of them correctly described the external appearance of the part they touched, thinking it was the whole elephant. In this way they were trying to describe the ‘morphology’ of this elephant. Morphology is the branch of Biology that deals with the study of the external form and structure of organisms.

                                     Fig: Story of elephant and bind people

Similarly, when you look at a plant, what are the parts you see with your naked eyes? List out the major parts with functions. 

                                                        Fig: Morphology of a plant

Phytomorphology is the branch of Biology that deals with the study of the form and structure of plants. A plant possesses different parts, such as the roots, stems, leaves, and flowers. All these parts have distinct functions in plant growth and development. Let’s take a deep dive into the details of morphology of plants and find out the various characteristics and functions of different parts of a plant in this particle.

Table of contents

• Plant kingdom
• Root system
• Shoot system
• Practice Problems
• FAQs

Plant kingdom

This kingdom includes multicellular, eukaryotic and producer organisms. They possess chlorophyll. They are mostly autotrophic. From microscopic plants to very complex and evolved forms, the kingdom Plantae includes a diverse range of species. The majority of the vegetation on Earth is made up of flowering plants. They are a collection of advanced and specialised groups. Every organ or component of the plant performs a specific task in the plant body. 

Parts of plant body

A plant body possesses two main fundamental parts as follows:

• Root system which is normally present below the ground.
• Shoot system which is normally seen above the ground.

Both systems function well in quite different environments. The plant's root system grows downward within the soil and aids the plant in anchoring. Leaves, stems, flowers, and fruits make up the shoot system.

Root system

The root system is the part of the plant axis that descends (grows downward) into the soil. When a seed germinates, the radicle is the first organ to appear. To form the primary or tap root, it grows longer. By growing lateral branches (secondary and tertiary roots), it establishes the root system. It deeply embeds the plant by spreading out into vast areas of soil. Another crucial job that it does is to bring water and mineral salts up from the soil. From the seed's radicle, the root system grows.

                                          Fig: root system develops from the radicle

Parts of the root system

It consists of the main root and its branches. The most prominent root present in the centre is called the primary root. It bears several lateral roots called secondary roots. These secondary roots further branches to form tertiary roots and finer rootlets. The tips of rootlets are normally covered with root caps. Behind the root tips it possesses fine outgrowth called root hairs. It is developed from the epiblema (epidermis of the root). 

                                          Fig: Parts of the root system

Root

All vascular plants have roots, which are their most significant underground component. This area of the plant is in charge of holding it firmly in place and absorbing essential nutrients, minerals, and water. Food can be stored in it as well. However, not all plants have underground roots; some also have above-ground roots called aerial roots. Mangrove plants, bonsai, and banyan trees are a few examples of plants with aerial roots. Roots play a crucial role in absorbing nutrients as well as anchoring and attaching the plant to various structures like trellises, rocks, and other nearby walls. 

                                       Fig: Buttress roots

Characteristics of root

Some of the important characteristics of the root are listed below:

• The root is a cylindrical, non-green portion of the plant that typically descends into the Earth.
• It is the first component to emerge from the plant's seed and develop through the radicle.
• In contrast to the general rule, in certain cases roots have buds that aid in vegetative propagation. For example sweet potato.
• At the end of the root, there is a root cap that aids in the protection of the root tip.
• They do not possess nodes or internodes.
• They possess root hairs.
• Roots exhibit positive geotropism. It shows growth towards gravity.
• Positive hydrotropism, or the growing movement toward the water, is evident in roots.
• In other words, they exhibit negative phototropism, or show growth away from light.

Functions of roots

Root performs two types of functions as follows:

• Primary functions
• Secondary functions

Primary or main functions of roots

Primary functions of the roots are as follows: 

• Absorption of water and minerals from the soil is an important function of the root. 
• They provide anchorage to plants.
• They help support the aerial shoot system of the plants. 
• The soil particles are held strongly by the root network that prevents soil erosion. 
• It also helps in synthesis of some of the plant growth regulators (PGRs).

Secondary or accessory functions of roots

The secondary or accessory functions of the root are as follows:

• Some of the plant roots get modified to store the reserve food materials. Examples include carrots and tapioca.

                            Fig: Carrot

• It provides extra mechanical support to the shoot system of plants. Examples include prop roots and stilt roots. 

        Fig: Prop roots in banyan tree

• Roots are involved in perennation in some plants. Examples include jasmine. 
• Roots of certain plants like leguminous plants are associated symbiotically with nitrogen-fixing bacteria which facilitate nitrogen fixation in the root nodules. 

                          Fig: Root nodules

• The roots of aquatic plants possess air-storing root structure to maintain the buoyancy of the plant and allow it to float. Examples include roots of the lotus plant. 
• Roots of certain plants get modified to perform photosynthesis. Examples include the velamen roots of orchids.

                      Fig: Velamen roots of orchids

• Parasitic plants have roots that derive nutrients from the hosts. Examples include Cuscutta, Loranthus etc.

                                            GIF: Parasitic roots of Cuscuta

• Roots of plants growing in marshy areas have their roots modified to help in respiration. Examples include Rhizophora. 

Fig: Respiratory root (pneumatophores) in Rhizophora

• Roots of certain plants support the plants in climbing by clinging to the fissures and cracks. Examples include Betel.

Shoot system

The shoot system is the ascending part of the axis that bears branches, leaves, flowers, and fruits. The shoot system is typically found above ground, however, it can also be modified to be found underground. It develops from the plumule part of the seed. 

              GIF: Shoot system develops from the plumule

Parts of the shoot system

The following are the main parts of the shoot system:

• Stem
• Leaves
• Flower
• Fruit

Stem

The ascending portion of a plant's axis that bears branches, leaves, flowers, and fruits is referred to as the stem.

Characteristics of stem

Some of the important characteristics of the stem are listed below:

• Older stems are heavy, woody, and dark brown, whereas younger stems are green and slender.
• They possess nodes, internodes, and buds. 
• The nodes are the locations from which new leaves and branches grow.
• The internodes are the spaces between nodes.
• The buds, which are immature young shoots with condensed axes, and the young leaves, which are crowded together and fold over the apex.
• The buds might be found terminally at the leaf axil or the tip of the stem. 
• Branches, new shoots, or flowers can all develop from a bud.
• It has both floral and vegetative buds, which are necessary for the plant's growth and to carry out sexual reproduction.

                               Fig: Structure of stem

Functions of stem

Some of the functions of the stem are listed below:

• In order to expose the leaves and branches to the most light possible, it holds them and supports them.

                      Fig: Leaves exposed to sunlight

• There are flowers and fruits on the stem and its branches.
• It facilitates the conduction of water, minerals, and photosynthetic products.
• To store food, stems can be modified. Examples include a potato.

                                                      Fig: Potato -Tuber

• Only a few plants can grow vegetatively by utilising stems. For example, Hibiscus and roses.

                               Fig: Hibiscus

• Opuntia plants have modified stems that are used for photosynthesis.

                                          Fig: Opuntia

• Climbers' stems, like those of cucurbits, Passiflora, and other plants, have been adapted to offer support to the plant. They have modified structures like tendrils. These are green thread-like and spirally coiled structures which are sensitive to touch. These help the weak stemmed plants to climb up against a solid support. Tendrils can be the modifications of buds like axillary or floral. 

 

                                   Fig: Stem tendrils

• Plants like lemon and Bougainvillaea possess thorns that are modified stems which help in defence. They are hard, pointed structures that develop on the axils of leaves. Thorns are modified axillary buds. 

                                                               Fig: Thorn

Leaf

It is characterised as a flat structure that is present on the stem. It develops at the node and bears a bud on its axil. 

                                      Fig: Structure of a leaf

Formation of leaves

The area of the embryo between the cotyledons known as the SAM (Shoot apical meristems) is where leaves are produced. Due to the presence of meristematic cells, multipotent stem cells, that can divide and differentiate into a variety of different cell types, SAM has the capacity to generate the entire shoot system.

                                              Fig: Shoot apical meristem (SAM)

The shoot's apical meristematic zone keeps increasing up the shoot as it expands, eventually taking up a position just above where the last set of leaves had grown. As a result, leaves develop acropetally, that is, one by one from base to tip.

                       Fig: Position of shoot apical meristem

Characteristics of leaf

Some of the characteristics of the leaf are listed below:

• The lateral outgrowths developed on the stems are commonly referred to as leaves.
• The nodes of the stem are where the leaves are produced.
• The growth of leaves is extremely limited and exogenous in origin.
• Buds can be found in the axils of leaves.
• The leaf is thought to produce food for the plant and is typically green in colour.

Functions of leaf

Some of the critical functions of leaves are as follows:

• Due to the chlorophyll present in them, the leaves are principally in charge of preparing food for the plant through the process of photosynthesis.
• Stomata on leaves assist in gas exchange and transpiration.

             GIF: Opening and closing of stomata

• In some plants like onion and garlic, leaves may be altered to store food. In succulents such as Aloe, the leaves store mucilaginous substances.

                         Fig: Bulb of onion

• Some plants with weak stems change their leaves into tendrils to provide support.

                                GIF: Tendrils coiling around a support

• In insectivorous plants, the portions of the leaves are specialised to trap insects. Examples include Venus flytrap (leaf lamina is bilobed and hinged to trap insects) and pitcher plant (leaf lamina is modified as a pitcher).

                                                              Fig: Insectivorous plants

• The leaves of Bryophyllum and Begonia contain adventitious buds that aid in vegetative reproduction.

Flower

A flower is a modified shoot with fewer internodes and more appendages sprouting from each node than a normal shoot would have. A stalk called a pedicel that connects flowers to the main stem. The apex produces a variety of floral appendages, including petals, stamens, carpels, and sepals.

                                      Fig: Flower

Characteristics of flower

Some of the important characteristics of a flower are listed below:

• A typical flower consists of four distinct whorls, such as calyx, corolla, androecium, and gynoecium.
• The outermost whorl of the flower is calyx, which is also known as sepals.
• The second whorl of a flower is the corolla which is also known as petals. This is the most colourful whorl.
• The third whorl of a flower is androecium which contains male reproductive organs called stamens.
• The fourth whorl of a flower is gynoecium which contains female reproductive organs called carpels.

                                                        Fig: Different whorls of a flower

Functions of flower

The critical functions of a flower are as follows:

• In angiosperms, the flowers are the regions where gametophytes grow.
• The ovary of the flower transforms into a fruit after fertilisation.
• The most crucial function of flowers is reproduction. They assist in the fusion of the male and female gametes.
• Flowers attract pollinating agents like birds and insects. 
• They provide food for the pollinating agents in the form of pollen grains and nectar.
• Flowers can encourage cross-fertilization, which is the union of male gamete and egg from other flowers. 

Fruit

It is a ripened ovary which is formed mostly after fertilisation. It is considered a unique feature of angiosperms. The fruit wall is called pericarp. It provides protection to the seeds. It helps in the dispersal of seeds. It possesses lots of nutrients and acts as a good food source. 

                                    Fig: Structure of fruit

Seed

It is a ripened ovule. It possesses an embryo, food reserves and seed coats. Outer seed coat called testa is formed from the outer integument. Inner seed coat called tegmen is formed from the inner integument. Embryo is the future plant. It possesses one or two cotyledons and an embryonal axis. Seeds provide nourishment to the embryo and protect it. It is the basis of agriculture. It can act as a food source. 

                                      Fig: Structure of seed

Practice Problems

Q 1. Identify the edible underground stem from the following options.

a. Potato
b. Carrot
c. Groundnut
d. Sweet potato
Answer: Potato is a modified stem. This modified stem develops underground and is known as a tuber. Hence, the correct option is a.

Q 2. Determine which is not a part of a leaf?

a. Lamina
b. Petiole
c. Stipules
d. Nodes
Answer: The leaf base is the portion of the leaf that connects to the stem. Stipules are a pair of tiny, leaf-like structures that some plants have at the base of their leaves. Stipules are regarded as a component of the leaf in anatomical terms in a typical flowering plant. A petiole is a name for the leaf's stem.

The leaf blade, also known as the enlarged green portion of the leaf, has veins and veinlets. It acts as the primary site of photosynthesis in the leaf lamina. The stem is not a part of the leaf; leaves are formed on the stem. Stem has internodes and nodes. The nodes on the stem is the region where leaves grow. Hence, the correct option is d.

Q 3. A flower is a modified ___________.

a. Root
b. Shoot
c. Leaf
d. Inflorescence
Answer: The flower is described as a modified shoot. Here, the shoot apical meristems convert into floral meristems. The floral meristems produce flowers. Hence, the correct option is b.

Q 4. How do flowers reproduce?
Answer: Pollination is the process through which flowers reproduce. This procedure involves the transfer of male gametes to ovules, where fertilisation takes place. Then the ovules develop into seeds inside a fruit.

FAQs

Q 1. Why are the leaves of some plants other than green in colour?
Answer: Usually the leaves of a plant are green in colour due to the presence of chlorophyll pigment. There are some plants that possess red to orange colour leaves because these plants possess carotene pigments along with chlorophyll.

Q 2. What would happen if plants lack leaves?
Answer: Without leaves, a plant will die since they are a vital component of the plant. A plant uses its leaves to exchange gases during the transpiration process. By using the process of photosynthesis, leaves also assist in preparing food for themselves.

Q 3. Why are petals a colourful part of a flower?
Answer: Flowers have genetic makeup, much like humans. These plants produce pigments, which result in a spectrum of colours. The carotenoid substance that gives tomatoes and carrots their colour also gives some flowers their yellow, red, or orange colour. This colouration is required to attract pollinating agents.

Q 4. Why do plants produce seeds?
Answer: In order to ensure the survival of the species, plants produce a lot of seeds. The embryo that subsequently develops into a new plant is present in the seed. Seeds result in genetic variations in plants. 

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