Root, Stem, and Leaves

Introduction:

Root, stem, and leaves are the morphology of plants. Morphology is the study of science that deals with the study of form, size, color, and position of respective parts of an organism. By learning the morphology characters of an organism we can identify living organisms, learn the variation between two organisms, if an organism is affected by some pathogen by looking at their morphology characters we can identify their diseases.

So today we are learning about the morphological part of plants which are root, stem, leaf, fruit, flower, and seed. But in this article we are just studying three plant parts they are root, stem, and leaf. We know the importance of these three parts as we learned about them in our high school but we are learning about them here more scientifically and deeply.

The root is the main part in plants for absorbing water and nutrition and transporting it to the stem. The root grows deep into the soil but it can’t be done in bedrock because rocks won’t allow them to go further, they stop growing deeply when they meet the bedrock layer.

The stem is the one that transports the nutrition, water, and some minerals to all parts of the plant. It bears leaves, fruits, and flowers. It spreads its branches and gives shelter to other living organisms too. Leaves play an important role in photosynthesis by which they prepare food. So let’s study more deeply about these three.

Overview:

Root, stem, and leaves are the morphology of plants. Morphology is the study of science that deals with the study of form, size, color, and position of respective parts of an organism. By learning the morphology characters of an organism we can identify living organisms, learn the variation between two organisms, if an organism is affected by some pathogen by looking at their morphology characters we can identify their diseases. we have learned about modifications, the morphology of the root, stem, and leaf which are more important in the plant.

Root, Stem, Leaf are plant parts. Other plant parts are fruit, flower, and seed. The underground part of the plant is the root which is growing towards soil with respect to gravitational force. The parts above ground are leaf, stem, flower, fruit, and seed which grow towards air opposite to gravitational force. In these, we are studying the underground part and the leaf and stem above-ground parts. Plants are the primary source of food in the world and the basic unit of the ecosystem. First, let’s study the root.

Root:

The vascular plant root is the organ that gives support to the whole plant and helps it to grow taller by transporting the nutrients, minerals, and water from the soil. They are basically below the soil but not always. Some plants bear aerials too in anaerobic conditions which makes them grow roots above ground. The main function of the root is to transport water, nutrients, and minerals to the plant from the soil and also to give support to the plant.

Root morphology:

Root morphology is divided into four parts. They are the root cap, apical meristem, elongation zone, and hair. These four root caps are the base part or first part of the root system.

• Root cap – helps to penetrate into the soil. As the roots go deeper they create a slimy surface that provides lubricant then the root cap is sloughed off.
• Apical meristem – it is present behind the root cap and produces new cells.
• Elongation zone – it is the area where new root cells increase their length and size. This region is further divided into three regions: cell division, area of elongation, and cell maturation.
• Hair-root cells are specialized structured hair that absorbs nutrients and water.

The true root consists of primary and secondary roots. Further, there are three types of root systems.

• Taproot system – it is the type of root system in which the main root is located in the center and lateral roots arise from them.
• Fibrous root system – bushy root branches from the main stem.
• Adventitious root – the root tissue that is formed from any non-root tissue is called adventitious root.

Modification of root:

• Tuberous root – adventitious root gets thick as the storage of food in them increases. Example: sweet potato
• Prop or pillar roots – roots are developed from horizontal branch pillar-like structures for extra support to the plants. Example: banyan
• Stilt roots – short and thick roots develop from basal nodes or better absorption of water and minerals.
• Clinging or climbing roots – the nonabsorptive roots which are found in climbers.
• Assimilatory roots – green roots that are able to perform photosynthesis.
• Parasitic roots – helps plants to absorb nutrients from hosts also known as sucking roots.
• epiphytic or aerial roots – the plants which live on other plant surfaces for food and shelter have this type of roots.
• Floating roots – it arises from each node of adventitious root in which some store air makes the plant float.

Stem:

The stem is the main structural vascular axis for plants which transport nutrients and water to all parts of the plant. It bears leaves, flowers, and fruits. It stores nutrients and produces more living tissues. In some plants, the stem is modified to store food, support vegetative propagation and protection.

Stem morphology:

The stem is normally divided into nodes and internodes. Node is the one that bears buds and leaves; sometimes branches also arise from them. Internode is the place between two nodes.

Stem modifications:

Based on the type of modifications stem modifications are of three types.

Underground stem modification:

• Rhizome: The stem is nongreen fleshy underground situated. The nodes have dry scale leaves with axillary buds. Adventitious roots arise from lower sides. Examples – banana, alocasia, ginger, turmeric.
• Bulb: Stem is highly condensed discoid. The upper surface has a terminal bud and there are many fleshy scale leaves. At the base adventitious roots are present. These bulbs can be tunicated or scaly. Examples – onion, garlic, lily.
• Corn: condensed rhizome that grows in a vertical direction. It is less spherical in shape and flattened at the base. It has circular nodes and internodes. The nodes have scales, leaves, and axillary buds and the adventitious roots are present in the base. Examples – colocasia, crocus.
• Tuber: The swollen tip of an underground lateral stem. The skin has several depressions which are known as eyes. Each eye is the anode and bears one more bud. Adventitious roots are absent. Examples – potato.

Sub-aerial modifications:

These modified stems are partially aerial and partially underground.

• Runner: creeping stems with long internode. They grow horizontally on the soil surface and bear scale leaves and adventitious roots. This type of stem arises from the axillary bud. Examples – lawn grass, etc
• Sucker: it arises from the basal underground part of the main stem. They grow horizontally for a distance below the soil and then grow upwards above the soil. Examples – chrysanthemum, mint, etc.

• Stolon: a weak lateral stem arises from the main stem base. After growing aerial, for some time it bent towards the ground and here terminal buds produce new shoots and adventitious roots. Examples – jasmine, colocasia, etc.
• Offset: offset is a short runner with a long internode. It develops from leaf axil and then grows horizontal branches which produce a rosette of leaves above and adventitious roots below. Examples – pistia etc.

Aerial stem modifications:

• Stem tendrils: stem modified into green thread-like leafless structures known as tendrils used for climbing. Examples – antigonon, etc.
• Thorns: these are pointed hard, woody structures that sometimes bear flowers and leaves. They are used for defending. Examples – citrus, dauranta, etc.
• Phylloclade: stem transforms to spine or scales and they also regulate transpiration. Examples – coccoloba, euphoria, etc.
• Cladophyll: it is also known as cladodes. They are flattened or cylindrical branches that help in photosynthesis. Examples – asparagus, etc.
• Bulbil: modified vegetative buds with stored food. It’s mainly for vegetative propagation. Examples – Dioscorea
• Thalamus: it is a condensed stem axis and bears floral organs.

Leaf:

The leaf is the main part of the plant which has nutrients and other minerals which are used to prepare edible portions for other parts. Leaves a major role in photosynthesis and transpiration. Leaves are collectively called foliage. Leaves have different shapes and sizes. Broad leaves, narrow leaves, etc. leaf is a flat structure that is attached to a branch or stem.

Morphology of leaves:

• Leaf base: the area where leaf petioles are attached. Two leaves stipulate a tiny structure found here.
• Petiole: where the leaf blade attaches to the base of the leaf.
• Leaf-blade/ lamina: main structure in leaf. Green in color. The leaf blade has a main vascular supply running in the center of the leaf called midrib; from here only leaf veins run. It is where chlorophyll, xanthophyll are present. Stomata is also present here.
• Venation: it is a pattern or shape in which the vascular system of the venules of the leaves is arranged.

Leaf modification: Where other structures of the plant are not performing or not developed then the plant leaves modify themselves to that function and it will also modify according to its habitat.

• Phyllode: petiole is modified as a leaf and also performs leaf functions. Examples – acacia, etc.
• Leaf spines: leaves are modified into spines or thorns for protection from predators. Examples – opuntia, etc.
• Tendrils: leaf modified to thread-like structures. Examples – Lathyrus, etc.
• Hooks: leaves transform into hooks for climbing purposes. Examples – bignonia unguis cati, etc.
• Insectivorous leaves: nitrogen is needed for some plants to grow. In that plant, leaves are modified to trap insects which become food to them. Examples – Venus flytrap, etc.

Importance of this chapter in NEET :

Plant morphology is the main topic that we need to know when learning about plants. Although it is a basic topic, you get many bits regarding modifications and their examples. It is easy to learn, and you will score high. You can expect questions related to this topic every year in competitive papers. Just learn modification types and their definitions with examples. Don’t neglect the definition of parts and the functions of morphological parts.

Also read: Flower, Fruit and Seed

FAQs

What is root?

In the vascular plant root is the organ that gives support to the whole plant and helps it to grow taller by transporting the nutrients, minerals, and water from the soil. They are basically below the soil but not always. Some plants bear aerials too in anaerobic conditions which makes them grow roots above ground. The main function of the root is to transport water, nutrients, and minerals to the plant from the soil and also to give support to the plant.

Q. What are the stem modifications?

Ans: Stem modifications:

Based on the type of modifications stem modifications are of three types.

1) Underground stem modification:

• Rhizome: Examples – banana, alocasia, ginger, turmeric.
• Bulb: Examples – onion, garlic, lily.
• Corn: Examples – colocasia, crocus.
• Tuber: Examples – potato

2) Sub-aerial modifications: These modified stems are partially aerial and partially underground.

• Runner: Examples – lawn grass, etc
• Sucker: Examples – chrysanthemum, mint, etc.
• Stolon: Examples – jasmine, colocasia, etc.
• Offset: Examples – pistia etc.

3) Aerial stem modifications:

• Stem tendrils: Examples – antigonon etc.
• Thorns: Examples – citrus, dauranta, etc.
• Phylloclade: Examples – coccoloba, euphoria, etc.
• Cladophyll: Examples – asparagus, etc.
• Bulbil: Examples – Dioscorea
• Thalamus: It is a condensed stem axis and bears floral organs.

Q. Write about leaf parts?

Ans: Morphology of leaf is as follows:

• Leaf base: the area where leaf petiole is attached. Two leaves stipulate a tiny structure found here.
• Petiole: where leaf blade attaches to the base of the leaf.
• Leaf-blade/lamina: main structure in leaf. Green in color. The leaf blade has a main vascular supply running in the center of the leaf called midrib; from here only leaf veins run. It is where chlorophyll, xanthophyll are present. Stomata is also present here.
• Venation: it is a pattern or shape in which the vascular system of the venules of the leaves is arranged.