Anatomy of Flowering Plants – Class 11 Biology Chapter 6 Notes & NCERT PDF

Class 11BiologyChapter 6NCERT book: Biology - Class 11

Notes and a simple summary of Chapter 6 of the NCERT Class 11 Biology book, with the official chapter PDF, flashcards, an MCQ quiz and an AI tutor for your doubts.

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Chapter 6: Anatomy of Flowering Plants

Introduction

Anatomy is the study of the internal structure of plants. Plants have cells as their basic unit; cells are organised into tissues, and tissues into organs. Different organs show differences in internal structure, and within angiosperms, monocots and dicots are anatomically different. Internal structures also show adaptations to diverse environments. This chapter studies tissues by their location (tissue systems) and then compares transverse sections (T.S.) of dicot and monocot roots, stems and leaves.

Key Concepts

6.1 The Tissue System

On the basis of structure and location there are three tissue systems:

Epidermal tissue system

Ground (fundamental) tissue system

Vascular (conducting) tissue system

#### 6.1.1 Epidermal Tissue System

Forms the outermost covering of the whole plant body: epidermal cells, stomata and epidermal appendages (trichomes and hairs).

Epidermis is usually single-layered, made of elongated, compactly arranged parenchymatous cells with a thin lining of cytoplasm and a large vacuole.

A waxy cuticle covers the outside and prevents water loss. Cuticle is absent in roots.

Stomata (in leaf epidermis) regulate transpiration and gaseous exchange. Each stoma has two bean-shaped guard cells enclosing the stomatal pore; in grasses guard cells are dumb-bell shaped.

Guard cells: outer walls thin, inner walls (towards pore) highly thickened; they possess chloroplasts and regulate opening and closing.

Specialised epidermal cells near guard cells = subsidiary cells. Stomatal aperture + guard cells + subsidiary cells = stomatal apparatus.

Root hairs are unicellular elongations of epidermal cells (absorb water and minerals). On the stem, epidermal hairs are trichomes – usually multicellular, branched or unbranched, soft or stiff, sometimes secretory; they help prevent water loss by transpiration.

#### 6.1.2 Ground Tissue System

All tissues except epidermis and vascular bundles form the ground tissue: parenchyma, collenchyma and sclerenchyma.

Parenchyma occurs in cortex, pericycle, pith and medullary rays of primary stems and roots.

In leaves, the ground tissue of thin-walled, chloroplast-containing cells is the mesophyll.

#### 6.1.3 Vascular Tissue System

Made of complex tissues xylem and phloem, which together form vascular bundles.

Open vascular bundles: cambium present between xylem and phloem (dicot stems) → can form secondary xylem and phloem.

Closed vascular bundles: no cambium (monocots) → no secondary tissues.

Radial arrangement: xylem and phloem on different radii, alternately (roots).

Conjoint arrangement: xylem and phloem on the same radius (stems, leaves); phloem usually only on the outer side of xylem.

6.2 Anatomy of Dicots and Monocots (T.S. of mature zones)

#### 6.2.1 Dicot Root (sunflower)

Outermost epiblema – many cells form unicellular root hairs.

Cortex: several layers of thin-walled parenchyma with intercellular spaces.

Endodermis: single layer of barrel-shaped cells, no intercellular spaces; tangential and radial walls have suberin deposited as casparian strips.

Pericycle: a few layers of thick-walled parenchymatous cells; lateral roots and vascular cambium (during secondary growth) arise here.

Pith small or inconspicuous; conjunctive tissue lies between xylem and phloem.

Usually two to four xylem and phloem patches; later a cambium ring develops.

Stele = all tissues inside the endodermis – pericycle, vascular bundles and pith.

#### 6.2.2 Monocot Root

Has epidermis, cortex, endodermis, pericycle, vascular bundles and pith.

Usually more than six (polyarch) xylem bundles; pith large and well developed.

No secondary growth.

#### 6.2.3 Dicot Stem

Epidermis with thin cuticle, may bear trichomes and a few stomata.

Cortex has three sub-zones: hypodermis (collenchyma – mechanical strength to young stem), cortical parenchyma (rounded thin-walled cells with intercellular spaces), and endodermis, rich in starch grains, so called the starch sheath.

Pericycle above the phloem as semi-lunar patches of sclerenchyma.

Medullary rays: radially placed parenchyma between vascular bundles.

Vascular bundles arranged in a ring; each is conjoint, open, with endarch protoxylem.

Large central pith of rounded parenchyma with large intercellular spaces.

#### 6.2.4 Monocot Stem

Sclerenchymatous hypodermis; many scattered vascular bundles, each surrounded by a sclerenchymatous bundle sheath; large parenchymatous ground tissue.

Bundles conjoint and closed; peripheral bundles smaller than central ones.

Phloem parenchyma absent; water-containing cavities present in bundles.

#### 6.2.5 Dorsiventral (Dicot) Leaf

Three main parts: epidermis, mesophyll, vascular system.

Upper = adaxial epidermis; lower = abaxial epidermis (usually more stomata; adaxial may lack stomata).

Mesophyll: palisade parenchyma (adaxial, elongated, vertical, parallel cells) and spongy parenchyma (oval/round, loosely arranged, large air spaces).

Vascular bundles in veins and midrib, surrounded by thick-walled bundle sheath cells; vein thickness varies (reticulate venation).

#### 6.2.6 Isobilateral (Monocot) Leaf

Stomata on both surfaces; mesophyll not differentiated into palisade and spongy.

In grasses, some adaxial epidermal cells along veins become large, empty, colourless bulliform cells. When turgid, the leaf surface is exposed; when flaccid (water stress), leaves curl inwards to reduce water loss.

Parallel venation → vascular bundles of nearly similar size (except main veins).

Diagrams to Know

Stomatal apparatus: bean-shaped guard cells (dicot) and dumb-bell shaped guard cells (grass), with pore, chloroplasts and subsidiary cells labelled.

Types of vascular bundles: radial, conjoint closed, conjoint open (cambium between xylem and phloem).

T.S. dicot root vs monocot root: epiblema with root hairs, cortex, endodermis, pericycle, protoxylem/metaxylem, phloem, pith (small in dicot, large in monocot).

T.S. dicot stem vs monocot stem: ring of bundles vs scattered bundles; hypodermis collenchymatous vs sclerenchymatous.

T.S. dicot vs monocot leaf: palisade and spongy mesophyll vs undifferentiated mesophyll; bulliform cells.

Key-Facts Sheet

Three tissue systems: epidermal, ground, vascular.

Cuticle absent in roots; root hairs unicellular; stem trichomes usually multicellular.

Casparian strips of suberin on endodermis of roots.

Stele = pericycle + vascular bundles + pith.

Dicot root: 2–4 xylem patches; monocot root: polyarch (more than six).

Dicot stem bundles: conjoint, open, endarch, in a ring. Monocot stem bundles: conjoint, closed, scattered, with bundle sheath; phloem parenchyma absent.

Endodermis of dicot stem = starch sheath.

Bulliform cells occur in grass leaves.

Exam Focus (from the chapter's exercises)

Draw and differentiate monocot vs dicot root and stem.

How to tell a monocot stem from a dicot stem in a section: scattered bundles with bundle sheath, closed bundles, no phloem parenchyma → monocot stem.

Define stomatal apparatus and draw a stoma.

Name the three tissue systems and the tissues in each.

Describe the internal structure of a dorsiventral leaf with a labelled diagram.

Key Terms

Anatomy (शारीरिकी), Epidermis (बाह्यत्वचा), Cuticle (उपत्वचा), Stomata (रंध्र), Guard cells (द्वार कोशिकाएँ), Subsidiary cells (सहायक कोशिकाएँ), Trichome (त्वचारोम), Mesophyll (पर्णमध्योतक), Endodermis (अंतस्त्वचा), Pericycle (परिरंभ), Stele (रंभ), Pith (मज्जा), Medullary rays (मज्जा रश्मियाँ), Vascular bundle (संवहन बंडल), Bulliform cells (आवर्ध त्वक कोशिकाएँ)

Common Mistakes

Saying the cuticle is present on roots – it is absent in roots.

Calling monocot stem bundles "open" – they are closed (no cambium).

Mixing up radial (roots) with conjoint (stems and leaves) bundles.

Forgetting that more stomata are usually on the abaxial (lower) surface of a dicot leaf.

Writing that monocot roots undergo secondary growth – they do not.

💡 Key Learning Points

✓Plant tissues are grouped by location into epidermal, ground and vascular tissue systems.
✓Stomatal apparatus consists of the stomatal pore, guard cells and subsidiary cells; guard cells are bean-shaped in most plants but dumb-bell shaped in grasses.
✓Vascular bundles may be radial (roots) or conjoint (stems and leaves), and open (with cambium) or closed (without cambium).
✓Dicot and monocot roots, stems and leaves differ in the number, arrangement and type of vascular bundles, pith size and mesophyll differentiation.
✓Special features like casparian strips, starch sheath and bulliform cells relate structure to function.

👨‍🏫 Teaching Tips

→Have students peel the lower epidermis of a leaf and observe stomata under a microscope; compare with a grass leaf.
→Cut thin transverse sections of a sunflower/balsam stem and a maize stem; stain and compare ring vs scattered bundles.
→Draw a comparison chart (as a list) of dicot vs monocot root, stem and leaf and revise it daily.
→Use colour coding in diagrams: xylem red, phloem blue, cambium green, to make open vs closed bundles obvious.
→Explain bulliform cells with a rolled-leaf demonstration using a grass leaf in dry vs wet conditions.
→Ask students to identify an unknown section using a checklist of features (exercise 3 style).
→Link tissue systems to functions by asking 'what would happen if this tissue were missing?'

📋 Assessment Questions

Can the student name the three tissue systems and the tissues in each?
Can the student distinguish open and closed, radial and conjoint vascular bundles?
Can the student draw and label T.S. of dicot and monocot root and stem?
Can the student identify a plant section from given anatomical features?
Can the student explain the role of guard cells, casparian strips and bulliform cells?

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← Previous: Chapter 5Morphology of Flowering Plants Next: Chapter 7 →Structural Organisation in Animals