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Plants may not have an immune system like animals, but they possess an efficient outer defense mechanism — protective tissues. These tissues shield delicate inner structures from external damage, dehydration, and pathogens.

This blog explores plant protective tissues, specifically the epidermis and cork (phellem) — a crucial topic in NEET Biology and NCERT Chapter: Anatomy of Flowering Plants.

What Are Protective Tissues?

Protective tissues are outermost cell layers in plants that:

Form a barrier against physical injury
Reduce water loss through evaporation
Protect against pathogen attacks
Provide structural support to aging tissues

Comparison with Animal Tissues:

Like epithelial tissue in animals, plant protective tissues cover surfaces and control exchange with the environment.

There are two primary types of protective tissues:

Epidermis
Cork (Phellem)

1. Epidermis – The First Line of Defense

Structure:

Single layer of tightly packed living cells
No intercellular spaces
Cuticle layer (made of waxy cutin) covers the surface
Contains stomata (pores) controlled by guard cells

Location:

Covers the outer surface of leaves, stems, roots, and young plant parts

Special Adaptations:

Roots: Epidermis develops root hairs to enhance absorption
Leaves: Guard cells regulate gas exchange and transpiration
Desert Plants (Xerophytes): Have a thick cuticle to prevent water loss

Function:

Acts as a barrier to mechanical injury
Prevents water loss via transpiration
Allows gas exchange through stomata
Protects against pathogens and UV radiation

2. Cork (Phellem) – Secondary Protective Layer

As the plant ages, the epidermis is replaced by cork tissue, especially in stems and roots undergoing secondary growth.

Structure:

Composed of dead cells
Cells have thick walls impregnated with suberin (waxy, waterproof substance)
No intercellular spaces or protoplasm

Formation:

Produced by a secondary meristem called cork cambium or phellogen
Cork, along with cork cambium and secondary cortex, forms the periderm

Location:

Found in older roots and stems
Replaces the epidermis during secondary growth

Function:

Prevents water loss
Acts as a thermal insulator
Provides mechanical strength to aging organs
Acts as a physical and microbial barrier

NEET Tips & One-Liners

Epidermis is the outermost living layer in young plant parts
Cuticle is made of cutin and helps reduce transpiration
Guard cells are the only epidermal cells with chloroplasts
Cork cells are dead, suberized, and impermeable
Suberin makes cork water- and gas-proof

Comparison Table: Epidermis vs Cork

NEET Practice Questions

Q1. Which plant tissue is made of dead, suberized cells and is impermeable to water and gases?

Xylem?
Phloem??
Cork
Parenchyma

Q2. In desert plants, the epidermis is covered with a thick layer of:

Starch
Lignin??
Cutin
Suberin

Q3. Guard cells are unique because:

They lack a nucleus
They are dead
They contain chloroplasts
They are absent in leaves

Q4. Suberin is found in:

Collenchyma
Cork cells
Sieve tubes
Xylem parenchyma

Q5. Cork replaces the epidermis in:

Young leaf
Root apex
Older stems
Root hairs

Conclusion

Although plants lack specialized epithelial tissues like animals, they have evolved epidermis and cork as effective protective tissues. These layers are vital for:

Conserving water
Fighting pathogens
Withstanding mechanical injury

Understanding these tissues is essential for cracking NEET biology questions and grasping deeper plant anatomy.

Revision Recap:

Epidermis = Living, cuticle-covered, controls gas exchange
Cork (Phellem) = Dead, suberized, insulates and waterproofs
Both form the protective barrier crucial for plant survival

Protective Tissues in Plants: Epidermis & Cork