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GNDU Question Paper-2021
BA/Bsc
1
st
Semester (Batch 2024-28) (CBGS)
BOTANY: Paper-I-B
(Diversity of Cryptogams)
Time Allowed: Three Hours Max. Marks:35
Note: Attempt Five questions in all, selecting at least One question from each section. The
Fifth question may be attempted from any section. All questions carry equal marks.
SECTION-A
1. Describe the typical modes of reproduction in bryophytes.
2. Write short notes on:
(i) Thallus structure in a thalloid bryophyte.
(ii) General features of Amphibians of Plants.
SECTION-B
3. Write an account of typical thallus structure and sporogonium in Anthoceros.
4. Write short notes on:
(i) Salient features of Marchantiales
(ii) Apical region in capsule of Funaria.
SECTION-C
5. Describe the typical life cycle of a heterosporous Pteridophyte.
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6. Write short notes on:
(i) Stele structure in Pteridophytes.
(ii) Important features of Sphenopsida.
SECTION-D
7. What is leptosporangiate development? Discuss the reproduction in a leptosporangiate
Pteridophyte.
8. Write short notes on:
(i) Economic importance of pteridophytes
(ii) Structure of sporangium in Equisetum.
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GNDU Answer Paper-2021
Bachelor of Computer Application (BCA) (Hons.)
1
st
Semester (Batch 2024-28) (CBGS)
BOTANY: Paper-I-B
(Diversity of Cryptogams)
Time Allowed: Three Hours Max. Marks:35
Note: Attempt Five questions in all, selecting at least One question from each section. The
Fifth question may be attempted from any section. All questions carry equal marks.
SECTION-A
1. Describe the typical modes of reproduction in bryophytes.
Ans: Describe the Typical Modes of Reproduction in Bryophytes
Bryophytes are small, green, non-flowering plants that include mosses, liverworts, and
hornworts. They are called the "amphibians of the plant kingdom" because they live on
land but need water for reproduction. Since they do not produce flowers, seeds, or fruits,
they reproduce by simple methods. Their reproduction is divided into three main modes:
Vegetative Reproduction, Asexual Reproduction, and Sexual Reproduction.
1. Vegetative Reproduction (Reproduction Without Spores or Sex Cells)
Vegetative reproduction is the simplest and fastest method of reproduction in bryophytes.
In this process, a new plant grows from the body of the parent plant without forming spores
or gametes (sex cells).
Imagine a small piece of moss breaking off after strong wind or rain. If this piece falls on
moist soil, it starts growing into a completely new moss plant. This is called fragmentation.
Some bryophytes also produce tiny green cup-like structures called gemmae. These
gemmae are small multicellular bodies that detach from the parent plant when raindrops
splash on them. Once they land on moist ground, they develop into new plants. This method
is common in liverworts such as Marchantia.
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Other methods include the formation of buds, tubers, or protonema, which also grow into
new plants under suitable conditions.
Key Points:
Only one parent is involved.
No spores or fertilization are needed.
Fast and efficient method.
Produces genetically identical plants.
2. Asexual Reproduction (By Spores)
Asexual reproduction in bryophytes mainly occurs through spore formation.
After the sporophyte develops on the parent plant, it produces a capsule called the
sporangium. Inside this capsule, special cells divide by meiosis to produce many tiny
haploid spores.
When the spores become mature, the capsule opens, and wind carries the spores to
different places. If a spore lands on moist soil, it germinates into a thread-like green
structure called the protonema (especially in mosses). The protonema later develops into a
mature bryophyte plant.
This method helps bryophytes spread over large areas because spores are very light and can
travel long distances.
Key Points:
Reproduction occurs through spores.
Spores are produced inside the capsule (sporangium).
Spores germinate into protonema.
One parent is involved.
3. Sexual Reproduction (By Fusion of Male and Female Gametes)
Sexual reproduction is the most important and complete method of reproduction in
bryophytes because it produces genetic variation.
The main green plant is called the gametophyte. It produces two reproductive organs:
Antheridium the male reproductive organ that produces motile sperm
(antherozoids).
Archegonium the female reproductive organ that contains a single egg (ovum).
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When rain or dew provides water, the sperm swim from the antheridium to the
archegonium because bryophytes require water for fertilization. The sperm fuses with the
egg to form a zygote.
The zygote develops into a sporophyte, which remains attached to the gametophyte and
depends on it for nutrition. The sporophyte eventually forms spores inside its capsule,
completing the life cycle.
Key Points:
Involves male and female reproductive organs.
Water is essential for fertilization.
Fertilization forms a zygote.
Zygote develops into a sporophyte.
Life Cycle of Bryophytes (Simple Diagram)
Mature Gametophyte
│
┌───────────────┴───────────────┐
│ │
Antheridium Archegonium
(Produces Sperm) (Contains Egg)
│ │
└────────── Water ──────────────┘
│
Fertilization
│
Zygote
│
Sporophyte
│
Capsule (Sporangium)
│
Meiosis
│
Spores
│
Germination
│
Protonema
│
New Gametophyte
Summary
Bryophytes reproduce in three different ways:
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1. Vegetative reproduction by fragmentation, gemmae, buds, or protonema,
producing new plants directly from the parent.
2. Asexual reproduction by forming spores inside a capsule, which germinate into
new plants.
3. Sexual reproduction by fusion of male and female gametes in the presence of
water, producing a zygote that develops into a sporophyte.
The dominant stage in the bryophyte life cycle is the gametophyte, while the sporophyte
depends on it for nutrition. Because water is essential for fertilization, bryophytes are
known as the amphibians of the plant kingdom.
Exam Tip
Remember this sequence:
Vegetative → Asexual (Spores) → Sexual (Gametes) → Zygote → Sporophyte → Spores →
New Gametophyte
This sequence is frequently asked in university examinations and helps explain the complete
reproductive cycle of bryophytes.
2. Write short notes on:
(i) Thallus structure in a thalloid bryophyte.
(ii) General features of Amphibians of Plants.
Ans: (i) Thallus Structure in a Thalloid Bryophyte
A thalloid bryophyte is a bryophyte (a simple, non-flowering plant) whose plant body is
called a thallus. Unlike higher plants, it does not have true roots, stems, or leaves. A
common example is Marchantia.
Imagine a flat, green ribbon lying on moist soil or a rock. That ribbon-like body is called the
thallus. It performs almost all the functions of the plant, such as making food, storing water,
and reproduction.
Structure of the Thallus
Dorsal (Upper) Surface
______________________________
/ Air Pores Air Chambers \
/________________________________\
| Photosynthetic Tissue |
|---------------------------------|
| Storage Tissue |
|_________________________________|
| | | |
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Rhizoids & Scales
Ventral (Lower) Surface
Explanation of Each Part
1. Flat, Green Body
The thallus is flat and green because it contains chlorophyll, which helps in photosynthesis
(making food from sunlight).
2. Dichotomous Branching
The thallus usually divides into two equal branches repeatedly. This type of branching is
called dichotomous branching. It helps the plant spread over a larger area.
3. Dorsal (Upper) Surface
The upper surface contains:
Air pores Tiny openings that allow gases like carbon dioxide and oxygen to move in
and out.
Air chambers Spaces filled with chlorophyll-containing cells where photosynthesis
occurs.
These pores remain permanently open, unlike stomata in higher plants.
4. Ventral (Lower) Surface
The lower side contains:
Rhizoids Hair-like structures that absorb water and minerals and anchor the plant
to the soil. They are not true roots because they lack vascular tissue.
Scales Thin, protective structures that help reduce water loss and protect the
growing region.
5. Internal Structure
Inside the thallus there are mainly two regions:
Photosynthetic region Located near the upper surface and rich in chlorophyll.
Storage region Located below it and stores food and water.
6. Reproduction
Special structures grow on the thallus:
Antheridiophore Produces male reproductive organs.
Archegoniophore Produces female reproductive organs.
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After fertilization, the new sporophyte develops on the female plant.
Easy Way to Remember
Think of a thalloid bryophyte as a small green carpet spread on damp ground.
The upper side captures sunlight and makes food.
The lower side holds the plant firmly with rhizoids.
The inside stores food and water.
Since it has no true roots, stems, or leaves, the entire thallus performs all life
functions.
(ii) General Features of Amphibians of Plants (Bryophytes)
Bryophytes are often called the "Amphibians of the Plant Kingdom." They are called
amphibians because, like frogs, they live on land but require water to reproduce.
Examples include Marchantia, Riccia, Funaria, and Mosses.
Why Are They Called Amphibians?
Imagine a frog.
It spends most of its life on land.
But it must return to water to lay eggs.
Bryophytes behave in a similar way.
They grow on land, especially in moist places.
However, water is essential for fertilization because the male reproductive cells
must swim through water to reach the female reproductive organ.
This is why they are called the amphibians of the plant kingdom.
General Features of Bryophytes
1. Small and Simple Plants
Bryophytes are generally small, soft, and green plants.
They do not have true roots, stems, or leaves.
Instead, they possess simple structures like rhizoids.
2. Lack of Vascular Tissue
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Bryophytes do not contain xylem and phloem, the tissues that transport water and food in
higher plants.
Therefore, they remain small and usually grow close to the ground.
3. Moist Habitat
They grow best in damp, shady places, such as:
River banks
Forest floors
Wet rocks
Tree trunks
4. Dominant Gametophyte
The gametophyte is the main green plant that we usually see.
The sporophyte remains attached to the gametophyte and depends on it for nutrition.
5. Water Needed for Fertilization
The male reproductive cells (antherozoids) are motile.
They swim through a thin layer of water to reach the female organ (archegonium).
Without water, fertilization cannot occur.
6. Reproduction by Spores
Bryophytes reproduce through spores, not seeds or flowers.
Spores are produced inside a capsule on the sporophyte.
When mature, they are released and grow into new plants.
7. Alternation of Generations
Bryophytes show alternation of generations, meaning their life cycle has two stages:
Gametophyte (haploid) Produces gametes.
Sporophyte (diploid) Produces spores.
These two generations alternate throughout the life cycle.
8. Ecological Importance
Bryophytes help:
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Prevent soil erosion.
Retain moisture in the soil.
Form new soil on bare rocks.
Provide habitat for tiny organisms.
Simple Diagram
BRYOPHYTE LIFE CYCLE
Spore
│
▼
Gametophyte (Green Plant)
│
┌──────┴──────┐
│ │
Antheridium Archegonium
(Male) (Female)
│ │
└────Water────┘
│
Fertilization
│
▼
Sporophyte
│
Capsule
│
Spores
Easy Way to Remember
Remember the sentence:
"Bryophytes live on land but marry in water."
This single line explains why they are called the amphibians of the plant kingdom.
They are simple, green plants without true roots, stems, leaves, or vascular tissues. They
reproduce by spores, and although they grow on land, water is essential for the movement
of male gametes during fertilization.
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SECTION-B
3. Write an account of typical thallus structure and sporogonium in Anthoceros.
Ans: Introduction
Anthoceros is a hornwort, a simple non-vascular plant that belongs to the group Bryophyta.
It is commonly found growing on moist soil, rocks, and damp places. The name Anthoceros
comes from two Greek words:
Anthos = Flower
Keros = Horn
It is called a hornwort because its sporogonium (spore-producing structure) looks like a
long, green horn growing upward from the plant body.
The body of Anthoceros is called a thallus because it is not divided into true roots, stems,
and leaves.
1. Typical Thallus Structure of Anthoceros
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The thallus is the gametophyte, which is the main and independent stage of the plant.
Shape and Size
The thallus is flat, green, and dorsiventral (it has an upper and a lower surface).
It is usually rosette-shaped and forms a mat on damp soil.
It branches by dichotomous branching, meaning one branch divides equally into two
branches.
Rhizoids
On the lower surface, smooth-walled rhizoids are present.
Rhizoids help the plant attach to the soil and absorb water and minerals.
Unlike liverworts, scales are absent in Anthoceros.
Internal Structure
When the thallus is cut across, it shows a simple internal structure.
The inside is made up of similar parenchymatous cells.
There is no clear separation into upper and lower tissues.
Each cell usually contains one large chloroplast with a pyrenoid.
What is a pyrenoid?
A pyrenoid is a small body inside the chloroplast that helps in storing food (starch) and
increases the efficiency of photosynthesis. This feature is similar to many green algae.
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Mucilage Cavities
Small cavities filled with mucilage (a jelly-like substance) are present inside the thallus.
These cavities often contain Nostoc, a blue-green alga (cyanobacterium).
The relationship is symbiotic:
Anthoceros provides shelter.
Nostoc fixes atmospheric nitrogen, supplying nitrogen to the plant.
This helps the plant grow even in nutrient-poor soil.
2. Sporogonium of Anthoceros
The sporogonium is the sporophyte generation. It develops after fertilization and remains
attached to the gametophyte.
Its horn-like appearance gives Anthoceros its common name.
The sporogonium has three main parts:
(A) Foot
The foot is the swollen basal part.
It remains embedded inside the gametophyte.
Its function is to absorb water and nutrients from the gametophyte.
(B) Meristematic Region
Just above the foot is a meristematic (actively dividing) region.
This is a special feature of Anthoceros.
Because of continuous cell division here:
The sporogonium keeps growing from the base.
It continues producing spores for a long time.
(C) Capsule
The capsule is long, narrow, and horn-shaped.
It contains:
Spores
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Pseudoelaters
Spores
Spores are produced by meiosis and help in reproduction.
When released, they germinate into new gametophyte plants.
Pseudoelaters
Pseudoelaters are long sterile cells.
They do not have spiral thickening like the elaters of liverworts.
Their function is to help in spore dispersal by changing shape as humidity changes.
Capsule Structure
Inside the capsule:
The center contains a sterile columella.
Around the columella lies the spore-producing tissue (archesporium).
This tissue produces spores and pseudoelaters.
When the spores mature:
The capsule dries.
It splits longitudinally into two valves.
The spores are gradually released into the air.
Simple Flow Diagram
Gametophyte (Thallus)
│
Fertilization
│
Sporogonium Develops
│
┌──────────────┐
│ Foot │ → Absorbs food
├──────────────┤
│ Meristem │ → Continuous growth
├──────────────┤
│ Capsule │
│ Columella │
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│ Spores │
│ Pseudoelaters │
└──────────────┘
│
Capsule splits into two valves
│
Spores released
│
New Thallus develops
Important Features to Remember
Feature
Description
Plant body
Flat, green thallus
Rhizoids
Smooth-walled, help in attachment and absorption
Scales
Absent
Chloroplast
One large chloroplast with a pyrenoid in each cell
Nostoc
Present in mucilage cavities for nitrogen fixation
Sporophyte
Long, green, horn-like sporogonium
Foot
Absorbs nutrients from gametophyte
Meristem
Causes continuous growth
Capsule
Produces spores and pseudoelaters
Columella
Sterile central column
Capsule opening
Splits into two valves
Conclusion
Anthoceros is one of the simplest bryophytes, but it has several unique features. Its thallus
is flat, green, and undifferentiated, with smooth rhizoids, a single large chloroplast
containing a pyrenoid, and mucilage cavities that house nitrogen-fixing Nostoc. The
sporogonium is long and horn-shaped, consisting of a foot, a continuously growing
meristematic region, and a capsule with columella, spores, and pseudoelaters. These
characteristics make Anthoceros different from other bryophytes and illustrate its efficient
method of growth, nutrition, and spore dispersal.
4. Write short notes on:
(i) Salient features of Marchantiales
(ii) Apical region in capsule of Funaria.
Ans: (i) Salient Features of Marchantiales
Introduction
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Marchantiales is an order of liverworts (Class: Hepaticopsida/Bryophyta). These are small,
simple, non-flowering plants that usually grow in moist and shady places, such as near
rivers, damp rocks, walls, and forest floors. Since they do not have true roots, stems, or
leaves, they absorb water directly from their surroundings.
A common example of Marchantiales is Marchantia.
Think of Marchantia as a green carpet spread over wet soil. Although it looks simple, it has
several special features that help it survive and reproduce.
Simple Diagram of Marchantia
Gemma Cup
( )
___|___
/ \
/ Thallus \
/_____________\
| | | | | | | |
Rhizoids (for attachment)
Scales (protect lower surface)
Salient Features of Marchantiales
1. Thalloid Plant Body
The plant body is called a thallus, which means it is flat, green, and ribbon-like. It is not
divided into roots, stems, and leaves.
Green in colour because it contains chlorophyll.
Performs photosynthesis to prepare food.
2. Dorsiventral Structure
The thallus has two different surfaces.
Upper (dorsal) surface: Green and contains air pores for gas exchange.
Lower (ventral) surface: Bears rhizoids and scales.
This arrangement helps the plant perform photosynthesis while remaining attached to the
soil.
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3. Rhizoids
Instead of true roots, Marchantiales have rhizoids.
Functions:
Attach the plant firmly to the ground.
Absorb water and minerals.
Rhizoids are unicellular (single-celled).
4. Air Pores and Air Chambers
The upper surface contains air pores leading to air chambers.
Functions:
Exchange gases.
Help in photosynthesis.
Air pores remain permanently open (unlike stomata).
5. Vegetative Reproduction
Marchantiales reproduce without seeds through gemmae.
Gemmae are:
Small green disc-like structures.
Produced inside gemma cups.
When rain splashes them away, they grow into new plants.
This is a very efficient way of producing many new plants.
6. Sexual Reproduction
Sexual reproduction occurs through specialized structures.
Antheridiophore → Produces male sex organs (antheridia).
Archegoniophore → Produces female sex organs (archegonia).
Water is necessary because the male gametes swim to reach the egg.
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7. Sporophyte Depends on Gametophyte
After fertilization, a sporophyte develops.
It has three parts:
Foot
Seta (small or absent)
Capsule
The sporophyte remains attached to the gametophyte and receives food from it.
8. Habitat
Marchantiales mostly grow in:
Moist soil
Damp rocks
River banks
Shady forests
They cannot survive for long in dry places.
9. Alternation of Generations
Their life cycle shows alternation of generations.
Gametophyte (green plant) is dominant.
Sporophyte develops after fertilization and produces spores.
Easy Trick to Remember Features
"T-R-A-G-S-S-H-A"
T → Thalloid body
R → Rhizoids
A → Air pores
G → Gemma cups
S → Sexual reproduction
S → Sporophyte dependent
H → Humid habitat
A → Alternation of generations
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Conclusion
Marchantiales are among the simplest land plants. Their flat thallus, rhizoids, air pores,
gemma cups, and water-dependent reproduction help them survive in moist environments.
Even though they appear small and simple, they represent an important stage in the
evolution of plants from water to land.
(ii) Apical Region in Capsule of Funaria
Introduction
Funaria is a common moss found on damp soil after the rainy season. Its sporophyte
consists of:
Foot
Seta
Capsule
The capsule is the spore-producing structure. At the top of the capsule is a special part
called the apical region, which helps in protecting and releasing spores.
Imagine the capsule as a small bottle filled with spores. The apical region acts like the cap
and lid of this bottle, ensuring spores are released only when conditions are suitable.
Simple Diagram of Capsule
Calyptra
▲
Operculum
___________
/ \
| Peristome |
|------------|
| Spore Sac |
|------------|
| Columella |
|____________|
|
Seta
Parts of the Apical Region
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1. Operculum (Lid)
The operculum is the cap-like lid covering the capsule.
Functions:
Protects immature spores.
Falls off when spores become mature.
2. Annulus
The annulus is a ring of thin-walled cells located below the operculum.
Function:
Dries up at maturity.
Helps the operculum detach easily.
It acts like a tear-away ring on a bottle cap.
3. Peristome Teeth
After the operculum falls, peristome teeth become visible.
Characteristics:
Usually 16 pairs (32 teeth).
Sensitive to moisture.
Functions:
Open in dry weather.
Close in humid weather.
Release spores gradually.
This controlled release ensures spores travel farther by wind.
4. Calyptra
The calyptra is a hood-like covering over the young capsule.
Functions:
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Protects the developing capsule.
Falls off when the capsule matures.
Importance of the Apical Region
The apical region performs several important functions:
Protects developing spores.
Controls the timing of spore release.
Prevents spores from being released all at once.
Increases chances of successful dispersal.
Helps in reproduction and survival of the species.
Working of the Apical Region
The process occurs in the following order:
1. Capsule matures.
2. Annulus dries.
3. Operculum falls off.
4. Peristome teeth become exposed.
5. Teeth open in dry weather.
6. Spores are released slowly by wind.
7. Teeth close again in moist weather.
This cycle repeats until all spores are dispersed.
Easy Memory Trick
Remember the sequence:
"C-A-O-P-S"
C → Calyptra
A → Annulus
O → Operculum
P → Peristome teeth
S → Spores released
Conclusion
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The apical region of the Funaria capsule is a highly specialized structure that ensures safe
development and efficient dispersal of spores. The calyptra protects the young capsule, the
annulus helps remove the lid (operculum), and the peristome teeth regulate spore release
according to humidity. This clever mechanism allows spores to spread over long distances
and gives Funaria a better chance of successful reproduction. Although Funaria is a simple
moss, its capsule demonstrates a remarkably efficient adaptation for life on land.
SECTION-C
5. Describe the typical life cycle of a heterosporous Pteridophyte.
Ans: The life cycle of a heterosporous pteridophyte is one of the most interesting topics in
botany because it shows how these plants reproduce and how they are considered an
important step in the evolution of seed plants.
What is a Heterosporous Pteridophyte?
Before understanding the life cycle, let's understand the meaning of the word.
Pteridophytes are vascular plants (plants with xylem and phloem) that reproduce
through spores instead of seeds. Examples include Selaginella, Isoetes, Marsilea,
and Salvinia.
Heterosporous means producing two different types of spores:
o Microspores small spores that develop into the male gametophyte.
o Megaspores large spores that develop into the female gametophyte.
This is different from homosporous pteridophytes, which produce only one type of spore.
Life Cycle of a Heterosporous Pteridophyte
The life cycle shows alternation of generations, meaning the plant has two stages:
1. Sporophyte Generation (Diploid 2n)
2. Gametophyte Generation (Haploid n)
These two stages alternate continuously.
Step 1: Mature Sporophyte (2n)
The sporophyte is the main, green, leafy plant that we normally see. It is independent and
performs photosynthesis to prepare its own food.
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It bears special reproductive structures called sporangia, which are arranged on modified
leaves known as sporophylls.
There are two types of sporangia:
Microsporangia produce microspores.
Megasporangia produce megaspores.
Step 2: Formation of Spores
Inside the sporangia, special cells called spore mother cells undergo meiosis.
As a result:
Microsporangia produce many microspores (n).
Megasporangia produce a few megaspores (n), usually four, but often only one
remains functional.
These spores are haploid (n) because meiosis reduces the chromosome number by half.
Step 3: Development of Gametophytes
After dispersal, the spores germinate.
A. Microspore → Male Gametophyte
The microspore develops into a tiny male gametophyte.
It forms antheridia, which produce many motile male gametes (antherozoids).
B. Megaspore → Female Gametophyte
The megaspore develops into the female gametophyte.
It produces archegonia, each containing one egg cell.
In many heterosporous pteridophytes, the female gametophyte develops inside the
megaspore, giving extra protection to the egg.
Step 4: Fertilization
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When water is available, the male gametes swim towards the archegonium.
One male gamete fuses with the egg.
This process is called fertilization.
The fusion forms a zygote (2n).
Step 5: Formation of Embryo
The zygote divides repeatedly by mitosis and develops into an embryo.
Initially, the embryo obtains food from the female gametophyte.
Gradually, it develops roots, stem, and leaves.
Step 6: New Sporophyte
The young sporophyte grows into an independent adult plant.
Once mature, it again forms microsporangia and megasporangia, repeating the life cycle.
Thus, the cycle continues generation after generation.
Simple Flow Diagram
Mature Sporophyte (2n)
│
Produces Sporophylls
│
┌────────────┴────────────┐
│ │
Microsporangium Megasporangium
│ │
└─── Meiosis ─────────────┘
│ │
Microspores (n) Megaspores (n)
│ │
Male Gametophyte Female Gametophyte
│ │
Antheridia Archegonia
│ │
Male Gametes ───────► Egg
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(Water helps movement)
│
Fertilization
│
Zygote (2n)
│
Embryo
│
Young Sporophyte
│
Mature Sporophyte (2n)
Important Features of Heterospory
Produces two types of spores (microspores and megaspores).
Forms separate male and female gametophytes.
Female gametophyte develops inside the megaspore, providing protection.
Considered an advanced feature compared to homospory.
It represents an important evolutionary step toward the development of seeds in
higher plants.
Examples of Heterosporous Pteridophytes
Selaginella
Isoetes
Marsilea
Salvinia
Azolla
Conclusion
The life cycle of a heterosporous pteridophyte begins with a diploid sporophyte, which
produces microspores and megaspores through meiosis. These spores develop into
separate male and female gametophytes. The male gametophyte forms sperm, while the
female gametophyte produces eggs. In the presence of water, fertilization occurs, forming a
diploid zygote that develops into an embryo and finally grows into a new sporophyte. This
alternation of generations ensures the continuation of the species and marks an important
evolutionary advancement because heterospory laid the foundation for the evolution of
seed-bearing plants.
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6. Write short notes on:
(i) Stele structure in Pteridophytes.
(ii) Important features of Sphenopsida.
Ans: (i) Stele Structure in Pteridophytes
The stele is the central vascular cylinder found inside the stem and root of a plant. It
contains the tissues that transport water, minerals, and food throughout the plant. In
simple words, you can think of the stele as the "transport system" or "highway" of the
plant.
Imagine a city where roads carry people and goods from one place to another. Similarly, the
stele carries water from the roots to the leaves and food prepared in the leaves to all other
parts of the plant. Without this transport system, the plant cannot survive.
Parts of a Stele
A typical stele consists of:
Xylem: Carries water and minerals from the roots to the upper parts of the plant.
Phloem: Transports prepared food from the leaves to all parts of the plant.
Pericycle: A protective layer surrounding the vascular tissues.
Pith (in some plants): Soft tissue present in the center for storage.
Types of Stele in Pteridophytes
Different pteridophytes have different types of steles depending on their evolution.
1. Protostele
This is the simplest and oldest type of stele.
Solid core of xylem in the center.
Phloem surrounds the xylem.
No pith is present.
Found in primitive pteridophytes like Lycopodium.
Phloem
***********
* Xylem *
* (Solid) *
***********
2. Siphonostele
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In this type, the center contains pith, and the vascular tissues form a ring around it.
Xylem surrounds the pith.
Phloem lies outside or on both sides of the xylem.
Found in many ferns.
Phloem
***************
* Xylem *
* --------- *
* | Pith | *
* --------- *
***************
3. Dictyostele
This is a more advanced type of siphonostele.
The vascular cylinder breaks into many separate vascular bundles.
These bundles form a network.
Common in advanced ferns.
O O O
O O O O
O O
(Many vascular bundles)
Importance of Stele
Transports water and food.
Gives mechanical support.
Helps plants grow taller.
Shows the evolutionary development of vascular plants.
Used by botanists for classification of pteridophytes.
Conclusion
The stele is the life-support system of pteridophytes. From the simple protostele to the
advanced dictyostele, its structure became more complex during evolution, making plants
stronger and better adapted to life on land.
(ii) Important Features of Sphenopsida
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Sphenopsida is a class of pteridophytes commonly known as horsetails. Today, the living
representative of this group is the genus Equisetum. These plants have existed since ancient
times and are often called living fossils because they have changed very little over millions
of years.
Imagine holding a small green bamboo-like plant with jointed stems. That is Equisetum.
Although it looks simple, it has many unique characteristics that make it different from
other pteridophytes.
Important Features
1. Jointed Stem
The stem is divided into nodes and internodes, giving it a bamboo-like appearance.
Green in color.
Performs photosynthesis because the leaves are very small.
2. Small Scale-like Leaves
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Leaves are tiny and scale-like.
Arranged in whorls around each node.
Since leaves are very small, the stem prepares food.
3. Whorled Branches
Branches arise in a circular pattern around each node.
This gives the plant a neat, symmetrical appearance.
4. Underground Rhizome
The plant has an underground stem called a rhizome.
It stores food.
Produces new shoots and roots.
5. Silica in Stem
One of the most special features is that the stem contains silica.
Because of silica:
Stem becomes rough.
It was traditionally used for cleaning and polishing utensils.
6. Reproduction by Spores
Sphenopsida does not produce flowers or seeds.
Instead:
Spores are produced.
Spores are formed inside sporangia.
Sporangia are arranged in a cone-like structure called a strobilus at the tip of the
stem.
Strobilus
/\
/__\
||
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||
======||======
Green Stem
||
Whorled
Branches
7. Well-developed Vascular Tissue
Xylem and phloem are well developed.
They efficiently transport water and food.
8. True Roots
Roots arise from the underground rhizome.
They absorb water and minerals from the soil.
9. Dominant Sporophyte
The sporophyte is the main and independent stage of the life cycle.
The gametophyte is small, short-lived, and develops from spores.
Importance of Sphenopsida
Represents one of the oldest groups of vascular plants.
Helps scientists understand plant evolution.
Prevents soil erosion with its underground rhizomes.
Used in botanical and evolutionary studies.
Some species have traditional medicinal and polishing uses.
Summary
Stele is the central vascular system of pteridophytes that transports water and food.
Its main types are Protostele (solid xylem), Siphonostele (with pith), and
Dictyostele (network of vascular bundles).
Sphenopsida (Equisetum) are ancient vascular plants with jointed green stems, tiny
whorled leaves, silica-rich stems, underground rhizomes, and spore-bearing cones
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(strobili). They are known as living fossils because they preserve many ancient plant
characteristics.
SECTION-D
7. What is leptosporangiate development? Discuss the reproduction in a leptosporangiate
Pteridophyte.
Ans: Introduction
Pteridophytes are the first vascular (xylem and phloem-containing) plants that reproduce
by spores instead of seeds. Ferns are the most common examples of pteridophytes. Among
them, most modern ferns show leptosporangiate development, which is considered a more
advanced type of sporangium (spore-producing structure) formation.
To understand this topic easily, imagine a fern as a plant that follows a two-generation life
cycle. One generation is the leafy fern plant that we usually see, and the other is a tiny
heart-shaped plant that helps in sexual reproduction.
1. What is Leptosporangiate Development?
The word Leptosporangiate comes from two Greek words:
Lepto = Thin or delicate
Sporangium = Spore-producing sac
So, leptosporangiate development means the formation of a small, thin-walled
sporangium from a single surface cell.
Unlike primitive ferns, where the sporangium develops from many cells, in leptosporangiate
ferns only one epidermal cell starts the entire development process.
Development Process
1. A single superficial (epidermal) cell becomes active.
2. It divides several times.
3. Some cells form the stalk of the sporangium.
4. The outer cells become the single-layered wall.
5. The inner cells develop into spore mother cells.
6. Each spore mother cell undergoes meiosis to produce four haploid spores.
Finally, the mature sporangium contains about 64 spores in most ferns.
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Characteristics of Leptosporangiate Sporangium
Develops from one initial cell.
Small and delicate in size.
Has a single-layered wall.
Usually has a long stalk.
Produces few spores (about 64).
Possesses a special ring of thick-walled cells called the annulus, which helps in
opening the sporangium and dispersing spores.
Simple Diagram of Leptosporangiate Sporangium
Mature Sporangium
____________
/ \
/ Spores \
| (64 spores) |
| |
|==== Annulus ====|
\______________/
||
||
Stalk
||
Fern Leaf
Annulus: Thick-walled cells that help burst the sporangium.
2. Reproduction in a Leptosporangiate Pteridophyte (Fern)
The reproduction of a leptosporangiate fern includes both asexual and sexual phases,
showing alternation of generations.
There are two plant bodies:
Sporophyte (2n) The large green fern plant.
Gametophyte (n) A tiny heart-shaped structure called the prothallus.
A. Sporophytic Phase (Asexual Reproduction)
The fern plant that we normally see is the sporophyte.
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Step 1: Formation of Sori
On the lower side of fern leaves are many brown spots called sori.
Each sorus contains many leptosporangia.
Fern Leaf
_______________________
o o o o o
o o o o o
o = Sori (clusters of sporangia)
Step 2: Formation of Spores
Inside each sporangium:
Spore mother cells undergo meiosis.
Four haploid spores are produced from each mother cell.
About 64 spores develop in one sporangium.
Step 3: Spore Dispersal
When the spores mature:
The annulus dries.
It contracts suddenly.
The sporangium bursts open.
Spores are scattered by the wind.
This helps the fern spread to new places.
B. Gametophytic Phase (Sexual Reproduction)
Step 4: Germination of Spores
When a spore lands on moist soil, it germinates and forms a small green heart-shaped plant
called the prothallus.
The prothallus is the gametophyte.
Prothallus
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______
/ \
/ \
| |
\ /
\________/
Heart-shaped Gametophyte
Step 5: Formation of Sex Organs
The prothallus produces two reproductive organs:
Antheridium (Male Organ)
Produces many motile antherozoids (sperms).
Archegonium (Female Organ)
Contains one egg cell.
Both organs are formed on the lower surface of the prothallus.
Step 6: Fertilization
Fertilization requires water.
When rain or dew is present:
Sperms swim through the water.
They reach the egg inside the archegonium.
Fusion of sperm and egg forms a zygote (2n).
Step 7: Formation of New Sporophyte
The zygote divides repeatedly.
It develops into:
Root
Stem
Leaves
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Gradually, it becomes a young fern plant.
The old prothallus eventually dies, and the new sporophyte grows independently.
Life Cycle Diagram
Mature Fern (Sporophyte 2n)
│
▼
Sori on Leaves
│
▼
Leptosporangia (Meiosis)
│
▼
Haploid Spores (n)
│
Germination
▼
Prothallus (Gametophyte n)
│ │
▼ ▼
Antheridium Archegonium
(Sperm) (Egg)
\ /
\ /
Fertilization
│
▼
Zygote (2n)
│
▼
Young Sporophyte
│
▼
Mature Fern
Important Features of Leptosporangiate Ferns
Sporangium develops from a single epidermal cell.
Wall is one cell thick.
Produces approximately 64 spores.
Annulus helps in spore release.
Life cycle shows alternation of generations.
Fertilization requires water because the sperm is motile.
The dominant plant body is the sporophyte, while the gametophyte (prothallus) is
small, green, and short-lived.
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Conclusion
Leptosporangiate development is the advanced method of sporangium formation found in
most modern ferns. In this process, the entire sporangium develops from a single surface
cell, resulting in a delicate stalked sporangium with a thin wall and an annulus that helps
release spores. Reproduction involves both asexual spore formation and sexual
reproduction through the prothallus, demonstrating a clear alternation of generations. This
life cycle allows ferns to reproduce efficiently and survive in moist environments, making
leptosporangiate ferns one of the most successful groups of pteridophytes.
8. Write short notes on:
(i) Economic importance of pteridophytes
(ii) Structure of sporangium in Equisetum.
Ans: (i) Economic Importance of Pteridophytes
Pteridophytes are seedless vascular plants. They have true roots, stems, and leaves, but
they do not produce flowers or seeds. Instead, they reproduce through spores. Common
examples are ferns, Equisetum (horsetail), Selaginella, and Lycopodium.
Although pteridophytes are not as economically important as flowering plants, they are still
very useful in many ways.
1. Ornamental Value
Many ferns have beautiful green leaves called fronds. Because of their attractive
appearance, they are grown in gardens, parks, offices, homes, and hanging baskets. They
improve the beauty of indoor and outdoor spaces.
Examples:
Nephrolepis (Boston Fern)
Adiantum (Maidenhair Fern)
Pteris
2. Medicinal Uses
Several pteridophytes are used in traditional medicine.
Equisetum is rich in silica and is used to strengthen bones, hair, and nails.
Dryopteris has been used to remove intestinal worms.
Some ferns are used for treating wounds, fever, skin diseases, and urinary disorders.
3. Food Source
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Some young fern leaves, called fiddleheads, are edible. They are eaten as vegetables in
many countries and also in some parts of India.
Example:
Diplazium esculentum is a popular edible fern.
4. Soil Conservation
The roots of pteridophytes help bind soil particles together. This prevents soil erosion,
especially on hillsides and riverbanks. They also improve soil fertility by adding organic
matter after decomposition.
5. Industrial Uses
The rough stems of Equisetum contain a large amount of silica.
They were traditionally used for cleaning and polishing metal utensils, wood, and
furniture. Therefore, Equisetum is also called the "Scouring Rush."
6. Fossil Fuel Formation
Ancient giant pteridophytes formed dense forests millions of years ago. After dying and
getting buried under the earth, they gradually changed into coal deposits. Thus, modern
coal owes much of its origin to ancient pteridophytes.
7. Scientific Importance
Pteridophytes are important for studying plant evolution because they form a link between
Bryophytes (non-vascular plants) and Gymnosperms (seed-producing plants). They help
scientists understand how vascular plants evolved.
Summary of Economic Importance
Importance
Use
Ornamental
Decoration in homes and gardens
Medicinal
Used in traditional medicines
Food
Young fern leaves eaten as vegetables
Soil Conservation
Prevent soil erosion
Industrial
Polishing materials (Equisetum)
Coal Formation
Ancient species formed coal deposits
Scientific
Study of plant evolution
(ii) Structure of Sporangium in Equisetum
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Equisetum, commonly called Horsetail, is a pteridophyte that reproduces through spores.
These spores are produced inside special structures called sporangia.
To understand the sporangium, imagine it as a tiny bag or capsule that stores spores until
they become mature.
Position of Sporangia
The sporangia are found in a cone-like structure called a strobilus, which is present at the
tip of the stem.
Inside the strobilus are many umbrella-shaped structures called sporangiophores.
Each sporangiophore bears 510 elongated sporangia on its lower surface.
Structure of the Sporangium
The sporangium has the following parts:
1. Sporangial Wall
It is a thin outer covering.
Usually consists of one layer of cells.
It protects the developing spores.
2. Sporogenous Tissue
Present inside the sporangium.
These cells divide by meiosis to produce numerous haploid spores.
3. Mature Spores
When mature, the spores become green because they contain chlorophyll.
They are spherical and very light.
4. Elaters
One unique feature of Equisetum spores is the presence of four ribbon-like appendages
called elaters.
Functions of Elaters
Help in spore dispersal by wind.
Open in dry weather and coil in moist weather.
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Prevent spores from clumping together.
Increase the chances of successful germination.
Dehiscence (Opening of the Sporangium)
When the spores become mature:
The sporangium dries.
The wall splits open lengthwise.
Spores are released into the air.
Wind carries them to suitable places where they germinate into a gametophyte.
Simple Diagram of Sporangium in Equisetum
Strobilus (Cone)
│
-------------------------
| | |
Sporangiophore Sporangiophore
(Shield-shaped)
_________
/ \
/ \
| |
\___________/
↓ ↓ ↓ ↓
┌─────────────────┐
│ Sporangia │
│ (Spore sacs) │
└─────────────────┘
│
┌────────────────┐
│ Sporangial Wall│
│ │
│ Sporogenous │
│ Tissue │
│ │
│ Mature Spores │
│ with Elaters │
└────────────────┘
Key Features of Equisetum Sporangium
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Feature
Description
Location
On the lower surface of sporangiophores in the strobilus
Shape
Long, sac-like structure
Wall
Thin, single-layered
Contents
Sporogenous tissue producing spores
Spores
Green, haploid, contain chlorophyll
Special Feature
Four hygroscopic elaters attached to each spore
Function
Produces and disperses spores for reproduction
Conclusion
Pteridophytes may not produce flowers or seeds, but they play an important role in nature,
medicine, industry, agriculture, and scientific research. Their ornamental beauty, medicinal
uses, contribution to coal formation, and role in preventing soil erosion make them
economically valuable.
The sporangium of Equisetum is a specialized spore-producing structure found inside the
strobilus. It consists of a protective wall enclosing sporogenous tissue, which develops into
spores. A unique feature of Equisetum spores is the presence of four hygroscopic elaters,
which help in efficient wind dispersal. Understanding the structure of the sporangium
explains how Equisetum successfully reproduces and spreads without producing seeds or
flowers.
This paper has been carefully prepared for educational purposes. If you notice any mistakes or
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