This MCQ module is based on: Permanent Tissues
TOPIC 22 OF 90
Permanent Tissues
🎓 Class 11
Biology
CBSE
Theory
Ch 6 – Anatomy of Flowering Plants
⏱ ~14 min
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Permanent Tissues
6.2.2 Permanent Tissues
Permanent tissues having all cells similar in structure and function are called simple tissues. Permanent tissues having many different types of cells are called complex tissues. Permanent tissues are derived from meristems and have lost the ability to divide.
6.2.2.1 Simple Tissues
A simple tissue is made of only one type of cells. The various simple tissues in plants are parenchyma, collenchyma, and sclerenchyma.
Parenchyma
Parenchyma forms the major component within organs. The cells of parenchyma are usually isodiametric. They may be spherical, oval, round, polygonal, or elongated in shape. Their walls are thin and made of cellulose. They may either be packed closely or have small intercellular spaces.
Parenchyma performs various functions like photosynthesis, storage, and secretion. Modified parenchyma:
- Chlorenchyma — parenchyma with chloroplasts; performs photosynthesis (e.g., in leaf mesophyll)
- Aerenchyma — parenchyma with large air spaces; provides buoyancy in aquatic plants (hydrophytes)
Collenchyma
Collenchyma occurs in layers below the epidermis in dicotyledonous plants. It is found either as a homogeneous layer or in patches. It consists of cells which are much thickened at the corners due to a deposition of cellulose, hemicellulose and pectin. Collenchymatous cells may be oval, spherical or polygonal and often contain chloroplasts. These cells assimilate food when they contain chloroplasts. Intercellular spaces are absent. They provide mechanical support to the growing parts of the plant such as young stems and petiole of leaves.
Sclerenchyma
Sclerenchyma consists of long, narrow cells with thick and lignified cell walls having a few or numerous pits. They are usually dead and without protoplast. On the basis of variation in form, structure, origin and development, sclerenchyma may be either fibres or sclereids.
The fibres are thick-walled, elongated and pointed cells, generally occurring in groups, in various parts of the plant. The sclereids are spherical, oval or cylindrical, highly thickened dead cells with very narrow cavities (lumen). These are commonly found in the fruit walls of nuts; pulp of fruits like guava, pear and sapota; seed coats of legumes and leaves of tea. Sclerenchyma provides mechanical support to organs.
| Feature | Parenchyma | Collenchyma | Sclerenchyma |
|---|---|---|---|
| Living/Dead | Living | Living | Dead |
| Cell shape | Isodiametric | Oval, spherical, polygonal | Long fibres or short sclereids |
| Cell wall | Thin, cellulosic | Thick at corners (cellulose+pectin+hemicellulose) | Thick, uniformly lignified |
| Intercellular space | Often present | Absent | Absent |
| Function | Storage, photosynthesis, secretion | Mechanical support + flexibility | Rigid mechanical support |
| Location | Throughout plant | Below epidermis (dicot stems, petioles) | Hard parts: nut shells, seed coats, fibres |
6.2.2.2 Complex Tissues
The complex tissues consist of more than one type of cells. These work together as a unit. Complex tissues are concerned with transportation of water, minerals, and food. There are two types: xylem and phloem.
Xylem
Xylem functions as a conducting tissue for water and minerals from roots to the stem and leaves. It also provides mechanical strength to the plant. It is composed of four different kinds of elements: tracheids, vessels, xylem fibres, and xylem parenchyma.
Tracheids are elongated, tube-like, dead cells with tapering ends and thick lignified walls. Vessels are long cylindrical tube-like structures, dead, made up of many cells called vessel members, each with lignified walls and large lumen. Tracheids and vessel members are perforated. Xylem fibres have thick walls and obliterated lumen and provide mechanical strength. Xylem parenchyma cells are living and store food (starch, fats) and other substances like tannins.
Primary xylem is of two types — protoxylem (the first formed primary xylem) and metaxylem (the later formed primary xylem). In stems, the protoxylem lies towards the centre (pith) and the metaxylem lies towards the periphery — this arrangement is called endarch. In roots, the protoxylem lies towards the periphery and metaxylem lies towards the centre — this is exarch.
Phloem
Phloem transports food materials, usually from leaves to other parts of the plant. Phloem is composed of sieve tube elements, companion cells, phloem parenchyma, and phloem fibres.
Sieve tube elements are long, tube-like structures, arranged longitudinally and are associated with the companion cells. End walls of sieve tube elements are perforated to form sieve plates. A mature sieve tube element possesses a peripheral cytoplasm and a large vacuole but lacks a nucleus. The functions of sieve tubes are controlled by the nucleus of companion cells.
Companion cells are specialised parenchymatous cells, which are closely associated with sieve tube elements. Phloem parenchyma stores food materials. Phloem fibres provide mechanical support. In gymnosperms, companion cells are absent; instead albuminous cells are associated with sieve cells. In monocots, phloem parenchyma is also absent.
| Feature | Xylem | Phloem |
|---|---|---|
| Function | Water + mineral transport (root → top) | Food transport (leaves → other parts) |
| Direction | Mainly upward (unidirectional) | Bidirectional (source-to-sink) |
| Conducting cells | Tracheids + vessels (dead) | Sieve tube elements (living, no nucleus) |
| Supporting cells | Xylem fibres + xylem parenchyma | Phloem fibres (bast) |
| Helper cells | — | Companion cells (alive, support sieve tubes) |
| Cell walls | Lignified, hard | Mostly cellulosic |
Interactive: Tissue Identifier
Pick a property — see which tissue it is:
Tissue: —
Pick living/dead and function.
Activity 6.2 — Sclereid Hunt
Setup: Take a small piece of guava or pear pulp. Crush gently and put on a slide. Add a drop of water.
Predict: What gives guava/pear pulp its slightly gritty/sandy texture? Which tissue cells will you see under the microscope?
You'll see: Among the soft parenchyma cells, hard, irregular, thick-walled cells with very narrow lumen — these are stone cells (sclereids), a type of sclerenchyma.
Why pear/guava feel gritty: The sclereids have hard lignified walls; they don't dissolve when chewed and feel like tiny grains.
Where else: Coconut shell (very dense sclereids), nut shells, seed coats of legumes, leaves of tea — wherever the plant needs hard, rigid protection.
Worked Examples
Worked Example 1: Why are Plants Strong but Flexible?
Compare collenchyma and sclerenchyma. Why do plants need both?
Collenchyma = LIVING cells with thickening at corners only (cellulose + pectin). Provides flexibility — young growing parts can bend in wind without breaking.
Sclerenchyma = DEAD cells with uniformly thick lignified walls. Provides rigid mechanical strength — needed in mature stems, leaf veins, fruit walls.
Why both are needed:
Sclerenchyma = DEAD cells with uniformly thick lignified walls. Provides rigid mechanical strength — needed in mature stems, leaf veins, fruit walls.
Why both are needed:
- Young growing organs need flexible support that doesn't restrict growth → collenchyma
- Mature organs need rigid permanent support → sclerenchyma
- Collenchyma can also do photosynthesis (chloroplasts present)
Worked Example 2: Phloem in a Cut Tree
If a tree's phloem is severed (e.g., by ring-girdling), what happens to the roots and why?
Phloem transports sugars from leaves to roots (and other non-photosynthetic parts). When severed:
Note: xylem (water transport) is still intact, so leaves get water briefly — but tree death is inevitable.
- No sugar reaches roots — root cells starve
- Root respiration continues using stored starch — depletes reserves
- Without energy, roots cannot maintain water uptake
- Eventually roots die → no water to leaves → tree dies (typically within months)
Note: xylem (water transport) is still intact, so leaves get water briefly — but tree death is inevitable.
Competency-Based Questions
Q1. Sieve tubes lack nucleus at maturity but are still functional because: L1 Remember
Answer: (b). Companion cells, connected via plasmodesmata, control the metabolic activity of enucleate sieve tubes.
Q2. The xylem of stems shows _________ arrangement: L2 Understand
Answer: (a) Endarch. Protoxylem is on the inner side (toward pith); metaxylem on outer side. In contrast, roots are exarch.
Q3. Distinguish parenchyma from collenchyma. L3 Apply
Parenchyma: Thin, cellulosic walls; intercellular spaces present; isodiametric; widely distributed; functions = storage, photosynthesis, secretion.
Collenchyma: Walls thick at corners (cellulose+pectin+hemicellulose); no intercellular spaces; oval/spherical/polygonal; below epidermis in dicot stems and petioles; function = mechanical support with flexibility.
Both are LIVING simple tissues but differ in wall thickness and primary function.
Collenchyma: Walls thick at corners (cellulose+pectin+hemicellulose); no intercellular spaces; oval/spherical/polygonal; below epidermis in dicot stems and petioles; function = mechanical support with flexibility.
Both are LIVING simple tissues but differ in wall thickness and primary function.
Q4. Analyse: Why do gymnosperms (conifers) lack vessels in xylem? Does this affect water conduction efficiency? L4 Analyse
Reason: Vessels evolved later than tracheids — gymnosperms are evolutionarily older than angiosperms. They have only tracheids; vessels are absent (with rare exceptions like Gnetales).
Efficiency: Tracheid water conduction IS less efficient — water must pass through pit pairs between adjacent tracheids. Vessels (in angiosperms) form continuous open tubes, conducting water 4-5x faster.
Compensation in conifers:
Efficiency: Tracheid water conduction IS less efficient — water must pass through pit pairs between adjacent tracheids. Vessels (in angiosperms) form continuous open tubes, conducting water 4-5x faster.
Compensation in conifers:
- Have evergreen needle leaves (transpire less)
- Tolerate cold, dry climates where slower transport is acceptable
- Tracheids resist embolism (gas bubble blockage) better than wide vessels
Q5. Create: Design a model showing how water moves through xylem from root to leaf using simple household items. L6 Create
Model Design:
- Materials: Many drinking straws (vessels), tissue paper bundle (tracheids), bowl with water (soil), cellophane stretched on a frame (leaf), fan (transpiration).
- Setup: Bind 8-10 straws into a "stem". Insert one end into water bowl. Top end touches cellophane "leaf" through a small slit.
- Transpiration: Aim fan at cellophane. As water evaporates from cellophane, water rises through straws (capillary + cohesion).
- Add coloured water: Watch the colour rise through straws — visualises continuous water column.
- Variation: Block a straw with chewing gum to demonstrate embolism — water in adjacent straws still flows (parallel paths).
Assertion–Reason Questions
Choose: (A) Both true, R explains A. (B) Both true, R doesn't explain A. (C) A true, R false. (D) A false, R true.
A: Sieve tube elements are unique among living plant cells.
R: They lack a nucleus at maturity but remain alive and functional.
Answer: (A). Both true; R explains A. Sieve tubes survive without nuclei because companion cells regulate them via plasmodesmata.
A: Sclerenchyma cells are dead at maturity.
R: Their cell walls are heavily lignified, leaving very narrow lumen.
Answer: (A). Both true; R explains A. Heavy lignin deposition obstructs cytoplasmic activity, leading to cell death; the dead cells then serve as rigid mechanical support.
A: Aerenchyma is found in aquatic plants.
R: The large air spaces in aerenchyma provide buoyancy and store oxygen.
Answer: (A). Both true; R explains A. Aerenchyma allows hydrophytes (water lily, lotus) to float and supplies oxygen to submerged tissues.
Frequently Asked Questions - Permanent Tissues
What is the main concept covered in Permanent Tissues?
In NCERT Class 11 Biology Chapter 6 (Anatomy of Flowering Plants), "Permanent Tissues" covers the core biological structures, functions, and classifications students need for board exam success. The MyAiSchool lesson explains the topic with definitions, labelled diagrams, comparison tables, and interactive simulations. Scientific terminology and ecological/physiological significance are highlighted throughout to build conceptual depth aligned with CBSE 2025-26 syllabus.
How is Permanent Tissues useful in real-life or applied biology?
Real-life applications of "Permanent Tissues" from NCERT Class 11 Biology Chapter 6 include medical diagnostics, agriculture, food preservation, biotechnology, ecological monitoring, and public health. The MyAiSchool lesson links every biological concept to a tangible application so students see biology as a problem-solving framework for living systems, not just textbook content.
What are the key terms students should memorize for Permanent Tissues?
Key terms in "Permanent Tissues" (NCERT Class 11 Biology Chapter 6 Anatomy of Flowering Plants) are tabulated in the MyAiSchool key-terms grid. Students should memorize each term with its precise definition, function, and example. Terminology is high-yield in CBSE board exams — 1-mark MCQs and 2-mark short answers test definitions directly. The Summary section provides a printable quick-reference card.
How does this part connect to other parts of Chapter 6?
NCERT Class 11 Biology Chapter 6 (Anatomy of Flowering Plants) is structured so each part builds biological understanding sequentially. "Permanent Tissues" connects to neighbouring parts via shared classifications, structural hierarchies, and physiological processes. The MyAiSchool lesson cross-references related concepts with internal links so students can navigate the whole chapter as one connected biological story rather than disconnected fragments.
What types of CBSE board questions come from Permanent Tissues?
CBSE board questions from "Permanent Tissues" typically include: (1) 1-mark MCQs on definitions and classification, (2) 2-mark short-answer differences/comparisons, (3) 3-mark labelled-diagram questions, (4) 5-mark long-answer essays combining structure + function + significance. The MyAiSchool lesson tags each Competency-Based Question (CBQ) with Bloom level (L1-L6) so students know how to study for each weight.
How can students use the interactive simulation effectively?
The interactive simulation in the "Permanent Tissues" lesson allows students to explore biological structures, classifications, or processes using selectors and sliders, with live visual feedback. To use it effectively: (1) explore each option/state, (2) compare with textbook diagrams, (3) note the function changes, (4) try the integrated practice quiz. The simulation reinforces visual-spatial understanding that pure text-based study cannot.
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