Apical Meristem - Structure, Defination, Overview

What is Apical Meristem?

Apical meristem is the region where the cells in the plant's roots and shoots divide very quickly and are highly undifferentiated at the tips. These cells help in primary growth, which makes the plants grow in two directions: upward (shoots) and downward (roots). Cell division in the apical meristem helps in the elongation and development of several organs of the plant.

Types of Apical Meristems

The apical meristems are of mainly two types:

Shoot Apical Meristem

• The shoot apical meristem is located at the tip of the plant shoot.

• It produces new stem tissues and flowers and leaves.

• In plants, this aids in upward growth.

Root Apical Meristem

• It is located at the root tip, it is covered with a root cap.

• This meristem aids in the downward movement of the root in soil.

Where is Apical Meristem Found?

Apical meristem is found in two chief parts of the plants:

• Shoot Apical Meristem: The shoot apical meristem is the tip of the shoot part of a plant.

• Root Apical Meristem: The root apical meristem is the tip of the root, behind its covering root cap.

Functions of Apical Meristem

The apical meristem performs very important functions in the growth and survival of a plant. Some of the primary functions are as follows:

• Cell Division: The apical meristem continuously divides generating new cells for growth.

• Primary Growth: The apical meristem provides vertical growth, directly causing an increase in the dimensions of the plant body.

• Differentiation: The cells produced by the apical meristem start to differentiate into other tissues like leaves, stems, and roots.

• Shoot and Root Growth: This promotes the elongation of shoots and roots. Hence it enables a plant to effectively capture sunlight (through shoots) and nutrient uptake (through roots).

What Happens if the Apical Meristem is Damaged/Cut?

• It usually interferes with plant growth, especially if damage to the apical meristem is extensive.

• Damage or cutting of the shoot apical meristem can cause the plant to stop growing upward.

• In some cases, lateral buds known as axillary buds become dominant and cause the plant to spread out horizontally rather than growing upwards.

• On roots, damage to the apical meristem inhibits root growth and thus affects the uptake of water and nutrients in the plant.

Structure of Shoot Apical Meristem

• Central Zone: Comprises cells that slowly divide and replace the stem cell population.

• Peripheral Zone: Comprises the formation of lateral structures like leaves and branches.

• Rib Meristem: Comprise in the formation of the stem below the meristem.

Structure of Root Apical Meristem

• Quiescent Center: It is a store of relatively quiescent cells and the reservoir for root growth.

• Proximal Meristem: Produces new cells and is responsible for the elongation of the root.

• Root Cap: It guards the apical meristem of the root as the root pushes its way through the soil.

Tips and Tricks to Learn Apical Meristem

To get a better understanding of the apical meristem concept, here are some tips and tricks:

• Study Aids: Draw diagrams showing where the root and shoot apical meristems are located, as well as the zones in each.

• Mnemonics: "Use SAM and RAM, where the Shoot Apical Meristem (SAM) is on top, and the Root Apical Meristem (RAM) has to be at the bottom.".

• Multimedia: View animations or videos illustrating how apical meristems stimulate growth in plants.

• Real-Life Example: Observe plant growth in the surroundings. For example, cutting the tip of a plant arrests its vertical growth but promotes side branching.

• Flashcards: Use flashcards to memorize key functions and zones of the apical meristem.

Exam Relevance

The weightage of questions related to apical meristem is given below:

Apical Meristem NEET MCQs

Q1. _______ is found at the tips of roots and shoots to produce primary permanent tissues.

1. Apical meristem

2. Intercalary meristem

3. Lateral meristem

4. Promeristem

Correct answer: 1) Apical meristem

Explanation:

The apical meristem is found at the tips of roots and shoots to produce primary permanent tissues.

Apical Meristems - These are found at the tips of roots and shoots to produce primary permanent tissues. They are responsible for an increase in the length of plant organs' primary growth. Root & Shoot developed into meristem. Meristem is divided into three regions

1. protoderm or demetogou - ex epidemic Root Hair, Steve Hair

2. procambium or plesome -

3. Ground meristems or periblem - Hydemis, Corter, endodermis, pericycle

Hence, the correct answer is option 1) Apical meristem.

Q2. Both apical meristem and intercalary meristem are _____ meristems.

1. Primary

2. Secondary

3. Lateral

4. Both 2 & 3

Correct answer: 1) Primary

Explanation:

Primary meristems include both intercalary and apical meristems. The plant grows taller or longer thanks to the apical meristem, which is located at the terminals of the roots and shoots. At the base of internodes or where the leaf attaches to the stem is the intercalary meristem. In those places, it promotes plant growth. Because they are in charge of the plant's primary growth, which increases in size and length, these meristems are referred to as primary. In the early phases of plant growth, primary meristems are crucial.

Hence, the correct answer is option 1) Primary.

Q3. Cells that are capable of continuous division are called

1. Meristematic cells

2. Permanent cells

3. Undifferentiated cells

4. Both 1 & 3

Correct answer: 4) Both 1 & 3

Explanation:

Both meristematic cells and undifferentiated cells possess the ability to divide continuously, yet they serve distinct functions and are situated in different contexts.

Meristematic Cells:
- Plant-specific, located in apical, lateral, and intercalary meristems.
- Facilitate plant growth via primary (elongation) and secondary (thickening) methods.
- Remain unspecialized, later forming specialized tissues.

Undifferentiated Cells:
- General term for cells without specific function.
- Examples include plant meristematic cells and animal stem cells (e.g., bone marrow).
- Function as a cellular reserve for organismal growth, repair, and regeneration.
- Differentiate into specialized cells when necessary.
Hence, the correct answer is option 4) Only 1 and 3

Read More:

• MCQs on Meristematic Tissues and its Type

• Monocot and Dicot Plants

• Sclerenchyma

FAQs on Apical Meristem

What do you mean by apical meristem?

The apical meristem is a region of actively dividing cells located at the tips of roots and shoots in plants. It is responsible for primary growth, meaning an increase in the length of the plant body. The cells of the apical meristem are small, thin-walled, and rich in cytoplasm, with a high capacity for cell division. These meristematic tissues give rise to different tissues of the plant body, enabling continuous growth throughout life.

Where is apical meristem found?

Apical meristems are found at the growing tips of roots and shoots. In roots, it is protected by a root cap, while in shoots, it is covered by young developing leaves. In some plants, apical meristems are also present in axillary buds and lead to branching. They ensure elongation of plant organs, thus helping the plant explore soil and light resources efficiently.

What are the functions of apical meristem?

The apical meristem plays a crucial role in plant growth and development. Its main functions are:

• Initiating primary growth by producing new cells for elongation of roots and shoots.

• Differentiating into various tissues such as epidermis, cortex, vascular tissues, etc.

• Forming leaves, flowers, and branches from shoot apical meristem.

• Allowing plants to adapt by continuously extending towards light (shoot) and water/nutrients (root).
  
  

What happens if the apical meristem is cut?

If the apical meristem of the shoot is cut or removed, the apical dominance (suppression of lateral buds by the apical bud) is lost. This leads to the growth of axillary or lateral buds, resulting in increased branching. This principle is used in horticulture and gardening practices such as pruning, to make plants bushier. In roots, removal of the apical meristem can arrest elongation, limiting growth in length.

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