# Anatomy of Flowering Plants (NEET Biology Class 11): Tissues, Xylem, Phloem & Vascular Bundles

Source: https://tracknation.in/story/anatomy-of-flowering-plants-neet-biology-class-11-tissues-xylem-phloem-vascular-bundles (TrackNation — free UPSC notes with PYQs)

> NEET Class 11 Anatomy, mined from NCERT: meristems, simple tissues (parenchyma, collenchyma, sclerenchyma), complex tissues xylem and phloem, the stomatal apparatus and trichomes, vascular bundle types (radial, conjoint, open/closed), the full dicot vs monocot root cross-section (epiblema, stele, polyarch), dicot vs monocot stem cross-section (starch sheath, bundle sheath), and dorsiventral vs isobilateral leaves (bulliform cells). Includes 15 MCQs, 7 NEET PYQs and recall.

## Meristems & Simple Permanent Tissues

📌 **NEET priority: Important.** *2–3 questions a year. Tissue types, the xylem/phloem components, and the dicot-vs-monocot vascular-bundle markers are the steady scorers — learn them precisely.*

Plant tissues are either **meristematic** (dividing) or **permanent**
(differentiated).

- **Meristems:** **apical** (tips of root/shoot → length),
**intercalary** (at internode bases, e.g. grasses), **lateral**
(vascular cambium & cork cambium → girth/secondary growth).

- **Simple permanent tissues** (one cell type):
**parenchyma** (thin walls; storage, photosynthesis),
**collenchyma** (corners thickened with cellulose/pectin; flexible support),
**sclerenchyma** (thick lignified walls, dead; mechanical strength — fibres &
sclereids).

## Complex Tissues — Xylem & Phloem

**Complex permanent tissues** are made of more than one cell type and form the
vascular tissue — each has **4 elements**:

| **Complex tissue**

 | **Components**

 | **Function**

 |
| Xylem

 | Tracheids, vessels, xylem parenchyma, xylem fibres

 | Water + mineral transport (upward)

 |
| Phloem

 | Sieve tubes, companion cells, phloem parenchyma, phloem fibres

 | Food (sugar) transport

 |

- **Xylem** conducts water; its conducting cells (tracheids, vessels) are
**dead** at maturity. **Protoxylem** forms first, **metaxylem**
later.

- **Phloem** conducts food; sieve tubes are living but enucleate, controlled by
the adjacent **companion cell**. (Gymnosperms lack vessels & companion cells.)

## Epidermal Tissue System & Vascular Bundle Types

Tissues group into three **tissue systems**: **epidermal**,
**ground**, and **vascular**.

### Epidermal tissue system — stomata and hairs

The single-layered epidermis is covered by a waxy **cuticle** (absent in roots) that
prevents water loss. **Stomata** sit in the leaf epidermis: each is formed of two
bean-shaped **guard cells** (dumb-bell shaped in grasses) enclosing the stomatal pore,
with surrounding **subsidiary cells** — together the **stomatal apparatus**.
Guard cells alone possess **chloroplasts** and control opening/closing. Root epidermal
cells extend into unicellular **root hairs** (water/mineral absorption); on the shoot,
epidermal hairs are **trichomes** — usually multicellular, may be branched, and reduce
water loss by transpiration.

### Vascular bundle types (key dicot/monocot markers)

- **Radial** — xylem and phloem on different radii (in **roots**).

- **Conjoint** — xylem and phloem on the same radius (in **stems**),
usually with phloem outside xylem.

- **Open** (cambium present → secondary growth) = **dicot stem**;
**closed** (no cambium) = **monocot stem**.

**Endodermis** cells carry **Casparian strips** (suberin bands) that
regulate water entry into the stele; just inside lies the **pericycle** (gives rise to
lateral roots).

## Root, Stem & Leaf Cross-Sections — Dicot vs Monocot

### Dicot root (e.g. sunflower) — outside to inside

**Epiblema** (outermost layer, bears root hairs) → **cortex**
(parenchyma with intercellular spaces) → **endodermis** (single layer of barrel-shaped
cells; Casparian strips) → **pericycle** → **xylem** (usually
**2–4 bundles**, di- to tetrarch) alternating with **phloem** →
small/inconspicuous **pith**. Everything inside the endodermis — pericycle, vascular
tissue, pith — together is the **stele**.

### Monocot root — the polyarch difference

Broadly similar layers to the dicot root, but with **more than 6 xylem bundles**
(**polyarch**) and a large, well-developed pith. Crucially,
**monocot roots never undergo secondary growth**.

### Dicot stem — the "ring" arrangement

Epidermis (cuticle, trichomes, few stomata) → **cortex** in three sub-zones:
collenchymatous **hypodermis** (mechanical strength), parenchymatous cortical layers,
and an innermost **endodermis rich in starch** (the "starch sheath") → pericycle as
**sclerenchyma patches** → vascular bundles (conjoint, **open**) arranged in
a characteristic **ring**, separated by parenchymatous **medullary rays** →
large parenchymatous **pith** at the centre. The **secondary growth occurs in most
dicotyledonous roots and stems**, driven by this open (cambium-bearing) vascular bundle
arrangement.

### Monocot stem — scattered and closed

A **sclerenchymatous** hypodermis, **scattered** vascular bundles (each
**conjoint and closed**, wrapped in a **sclerenchymatous bundle sheath**),
and a large conspicuous parenchymatous ground tissue. Peripheral bundles are smaller than central
ones; **phloem parenchyma is absent**, and the bundles often contain water-storing
cavities.

### Leaf anatomy — dorsiventral vs isobilateral

- **Dorsiventral (dicot) leaf:** mesophyll is differentiated into an upper
**palisade parenchyma** (elongated, vertically arranged) and a lower, loosely-packed
**spongy parenchyma** with large air spaces. The **abaxial** (lower)
epidermis usually has more stomata than the **adaxial** (upper) surface.

- **Isobilateral (monocot) leaf:** stomata occur on **both**
surfaces equally; the mesophyll is **not** differentiated into palisade and spongy
layers. Grasses have large, empty **bulliform cells** on the adaxial epidermis along the
veins — when turgid (water-rich) the leaf stays flat; when they lose water and go flaccid, they curl
the leaf inward to cut water loss.

### The plant tissue systems — complete reference table

| **Tissue system**

 | **Tissues included**

 | **Key features**

 |
| EPIDERMAL tissue system

 | Epidermal cells, stomata, epidermal appendages (root hairs, trichomes)

 | Outermost covering, usually a SINGLE layer, with a waxy CUTICLE (absent in roots). Stomata regulate transpiration and gas exchange

 |
| GROUND tissue system

 | Parenchyma, collenchyma, sclerenchyma — as cortex, pericycle, pith and medullary rays

 | All tissues EXCEPT epidermis and vascular bundles. In leaves, ground tissue = MESOPHYLL (photosynthetic)

 |
| VASCULAR tissue system

 | Xylem and phloem, together forming vascular bundles

 | Xylem conducts water/minerals; phloem conducts food. Arrangement differs between root, stem and dicot/monocot

 |

| **Simple tissue**

 | **Cell wall**

 | **Function**

 | **Where found**

 |
| Parenchyma

 | Thin cellulose walls, living cells with intercellular spaces

 | Photosynthesis, storage, secretion

 | Cortex, pith, mesophyll

 |
| Collenchyma

 | Thickened at the CORNERS with cellulose, hemicellulose and pectin; living

 | MECHANICAL SUPPORT to growing parts; may contain chloroplasts

 | Below epidermis in dicot stems and leaf stalks

 |
| Sclerenchyma

 | Thick LIGNIFIED walls; DEAD cells at maturity, often without protoplasts

 | Mechanical support — the strongest support tissue

 | As fibres and sclereids (e.g. in nut walls, pulp of guava/pear)

 |

### Why this matters for NEET

- "Identify: dicot or monocot?" from a described cross-section is a classic NEET question
format — the scattered-bundle + sclerenchymatous-sheath + no-phloem-parenchyma combination
**always** means monocot stem.

- Traps: sclerenchyma is **dead**; companion cells are unique to
**angiosperm** phloem; **monocot roots/stems don't undergo secondary growth**;
Casparian strips are in the **endodermis**, not the epidermis; bulliform cells help the
leaf **curl**, they don't open stomata.

## Test Yourself: MCQs, PYQs & Active Recall

Answer these, then close the article and do an Active Recall. Reveal each answer only after you commit to one.

## Practice Questions

**Q1.** Which simple tissue provides mechanical strength and is dead at maturity?

- (a) Parenchyma

- (b) Aerenchyma

- (c) Sclerenchyma

- (d) Collenchyma

**Answer: (c)** — Sclerenchyma has thick lignified walls and is dead — it gives mechanical support (fibres and sclereids).

**Q2.** Collenchyma is characterised by:

- (a) Sieve plates

- (b) Lignified walls

- (c) Dead cells

- (d) Thickening at the corners with cellulose and pectin

**Answer: (d)** — Collenchyma has cellulose/pectin thickening at the corners and gives flexible support to growing parts.

**Q3.** Which are the conducting components of xylem?

- (a) Tracheids and vessels

- (b) Sieve tubes and companion cells

- (c) Parenchyma only

- (d) Fibres only

**Answer: (a)** — Xylem conducts water through tracheids and vessels (dead at maturity); it also has xylem parenchyma and fibres.

**Q4.** Companion cells are associated with:

- (a) Vessels

- (b) Tracheids

- (c) Sclereids

- (d) Sieve tube elements

**Answer: (d)** — Each sieve tube element is controlled by an adjacent living companion cell (both in phloem).

**Q5.** Radial vascular bundles are typically found in:

- (a) Dicot stems

- (b) Roots

- (c) Leaves

- (d) Monocot stems

**Answer: (b)** — In roots, xylem and phloem lie on different radii — a radial arrangement.

**Q6.** Open vascular bundles (with cambium) are characteristic of:

- (a) Roots

- (b) Dicot stems

- (c) Monocot leaves

- (d) Monocot stems

**Answer: (b)** — Dicot stems have open bundles (cambium present), enabling secondary growth; monocot bundles are closed.

**Q7.** Casparian strips are present in the:

- (a) Pericycle

- (b) Pith

- (c) Epidermis

- (d) Endodermis

**Answer: (d)** — The endodermis bears Casparian strips of suberin that regulate water movement into the stele.

**Q8.** Intercalary meristem is mainly responsible for:

- (a) Formation of cork

- (b) Growth in length at internodes

- (c) Lateral roots

- (d) Increase in girth

**Answer: (b)** — Intercalary meristem (at internode/leaf bases, e.g. grasses) adds length; lateral meristem adds girth.

**Q9.** Scattered vascular bundles are a feature of:

- (a) Dicot root

- (b) Monocot stem

- (c) Dicot stem

- (d) Dicot leaf

**Answer: (b)** — Monocot stems have scattered, closed vascular bundles; dicot stems have them in a ring.

**Q10.** The stomatal apparatus consists of:

- (a) Guard cells, stomatal pore and subsidiary cells

- (b) Only the guard cells

- (c) Cuticle and trichomes

- (d) Only the epidermis

**Answer: (a)** — The stomatal aperture, guard cells, and surrounding subsidiary cells together form the stomatal apparatus.

**Q11.** In grasses, the guard cells are typically:

- (a) Absent

- (b) Bean-shaped

- (c) Dumb-bell shaped

- (d) Spherical

**Answer: (c)** — Most plants have bean-shaped guard cells, but grasses have distinctive dumb-bell shaped guard cells.

**Q12.** The outermost layer of a dicot root, bearing root hairs, is the:

- (a) Pericycle

- (b) Endodermis

- (c) Cortex

- (d) Epiblema

**Answer: (d)** — The epiblema (root epidermis) is the outermost layer; many of its cells extend into unicellular root hairs.

**Q13.** All the tissue inside the endodermis — pericycle, vascular bundles, and pith — is collectively called the:

- (a) Hypodermis

- (b) Cortex

- (c) Mesophyll

- (d) Stele

**Answer: (d)** — The stele includes everything inside the endodermis: pericycle, vascular tissue, and pith.

**Q14.** Bulliform cells, found in grass leaves, function to:

- (a) Form the vascular bundle sheath

- (b) Produce chlorophyll

- (c) Conduct water

- (d) Help the leaf curl inward under water stress

**Answer: (d)** — Turgid bulliform cells keep the leaf flat; when they lose water and go flaccid, the leaf curls inward to minimise water loss.

**Q15.** The endodermis of a dicot stem, rich in starch grains, is also called the:

- (a) Starch sheath

- (b) Pericycle

- (c) Bundle sheath

- (d) Hypodermis

**Answer: (a)** — The innermost cortical layer (endodermis) of a dicot stem is starch-rich and is called the starch sheath.

**Q16.** The stems shown in P and Q are respectively

- (a) dicot stem and dicot root

- (b) monocot stem and dicot stem

- (c) monocot stem and monocot root

- (d) dicot stem and monocot stem

**Answer: (d)** — P has vascular bundles arranged in a ring with a cambium; Q has numerous scattered bundles, each surrounded by a sclerenchymatous bundle sheath — the monocot stem.

**Q17.** The tissue marked A, lying between xylem and phloem in P, is

- (a) cambium

- (b) pericycle

- (c) protoxylem

- (d) endodermis

**Answer: (a)** — A is the cambium. Its presence makes the dicot vascular bundle 'open' — capable of secondary growth. Monocot bundles have no cambium and are 'closed'.

**Q18.** Which of the following is true for the stem marked Q?

- (a) Secondary growth takes place by a vascular cambium

- (b) Vascular bundles are arranged in a ring and open

- (c) Xylem and phloem are on different radii

- (d) Vascular bundles are scattered and closed, with a sclerenchymatous sheath

**Answer: (d)** — In a monocot stem the bundles are scattered in the ground tissue, are conjoint and closed (no cambium), and are surrounded by a sclerenchymatous bundle sheath [D]; so there is no secondary growth.

### NEET Previous Year Questions (PYQs)

*Real NEET previous-year questions on this chapter, with explanations in our own words.*

**Q19.** Which of the following is a dead mechanical tissue? (NEET PYQ)

- (a) Collenchyma

- (b) Sclerenchyma

- (c) Parenchyma

- (d) Chlorenchyma

**Answer: (b)** — Sclerenchyma cells are dead with lignified walls — purely mechanical.

**Q20.** Secondary growth normally occurs in: (NEET PYQ)

- (a) Most dicotyledonous roots and stems

- (b) Monocot stems

- (c) Neither dicots nor monocots

- (d) Monocot roots

**Answer: (a)** — NCERT states secondary growth occurs in most dicotyledonous roots and stems; monocot roots/stems lack it.

**Q21.** The pericycle gives rise to: (NEET PYQ)

- (a) Cork

- (b) Companion cells

- (c) Stomata

- (d) Lateral roots

**Answer: (d)** — Lateral roots and part of the vascular cambium originate from the pericycle.

**Q22.** A monocot stem cross-section shows scattered, closed bundles with a sclerenchymatous bundle sheath and no phloem parenchyma. This tissue is from a: (NEET PYQ)

- (a) Monocot stem

- (b) Dicot root

- (c) Dicot stem

- (d) Monocot root

**Answer: (a)** — This exact combination — scattered, closed vascular bundles with a sclerenchymatous bundle sheath and absent phloem parenchyma — identifies a monocot stem.

**Q23.** Companion cells and sieve tubes are absent in: (NEET PYQ)

- (a) Angiosperms

- (b) Monocots

- (c) Gymnosperms

- (d) Dicots

**Answer: (c)** — Gymnosperms lack vessels in xylem and sieve tubes/companion cells in phloem (they have tracheids & albuminous cells).

**Q24.** In a dicot root the number of xylem bundles is usually: (NEET PYQ)

- (a) Eight to twelve

- (b) One

- (c) Two to four

- (d) More than six

**Answer: (c)** — Dicot roots are di- to tetrarch (2–4 xylem bundles); monocot roots are polyarch (many).

**Q25.** The tissue system that includes cortex, pith and mesophyll is the: (NEET PYQ)

- (a) Vascular tissue system

- (b) Epidermal tissue system

- (c) Dermal system

- (d) Ground tissue system

**Answer: (d)** — Cortex, pericycle, pith and mesophyll all belong to the ground tissue system.

### Active Recall Prompt

Write everything you can recall, naming each topic first. Cover: **meristems** (apical, intercalary, lateral); the three **simple tissues** (parenchyma, collenchyma, sclerenchyma); the **complex tissues** xylem and phloem with their components; **stomata, trichomes and root hairs**; **vascular bundle types** (radial, conjoint, open/closed); the **dicot vs monocot root cross-section** (epiblema, endodermis, stele, polyarch); the **dicot vs monocot stem cross-section** (ring vs scattered, starch sheath, bundle sheath); and the **dorsiventral vs isobilateral leaf** (palisade/spongy, bulliform cells). Begin each fact with its topic and end it with a full stop.