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Updated 6 August 2026

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Plant Kingdom — NCERT Solutions

CBSE · Class 11 · Biology

NCERT Solutions for Plant Kingdom, CBSE Class 11 Biology: 11 textbook questions solved step by step. Covers Exercises.

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Exercises

1What is the basis of classification of algae?Show solution

Given: We need to identify the basis on which algae are classified.

Concept: Algae are classified based on two main criteria:

Type of pigment (photosynthetic pigments) present in the cell.
Type of stored food (reserve food material).

Classification:

Class	Pigments	Stored Food
Chlorophyceae (Green algae)	Chlorophyll a, b; carotenoids	Starch
Phaeophyceae (Brown algae)	Chlorophyll a, c; fucoxanthin	Mannitol, laminarin
Rhodophyceae (Red algae)	Chlorophyll a, d; phycoerythrin	Floridean starch

Additional bases include the nature of the cell wall, flagellation of reproductive cells, and the type of sexual reproduction (isogamy, anisogamy, or oogamy).

Conclusion: The primary basis of classification of algae is the type of photosynthetic pigments and the nature of stored food material.

2When and where does reduction division take place in the life cycle of a liverwort, a moss, a fern, a gymnosperm and an angiosperm?Show solution

Given: We need to identify the site and time of meiosis (reduction division) in five different plant groups.

Concept: Reduction division (meiosis) occurs during spore formation (sporogenesis) in all embryophytes. The location differs based on the dominant generation.

(i) Liverwort:

When: During spore formation.
Where: In the sporophyte (capsule), specifically in the spore mother cells (sporocytes) inside the capsule (sporangium). Meiosis produces haploid spores.

(ii) Moss:

When: During spore formation.
Where: In the capsule of the sporophyte, in the spore mother cells present in the sporangium. Meiosis produces haploid spores.

(iii) Fern (Pteridophyte):

When: During spore formation.
Where: In the sporangia borne on the leaves (sporophylls) of the sporophyte. Meiosis occurs in the spore mother cells within the sporangia.

(iv) Gymnosperm:

When: During the formation of microspores and megaspores.
Where:
In microsporangia (on microsporophylls of male cones) — meiosis in microspore mother cells produces haploid microspores (pollen grains).
In megasporangia/ovules (on megasporophylls of female cones) — meiosis in megaspore mother cells produces haploid megaspores.

(v) Angiosperm:

When: During the formation of microspores and megaspores.
Where:
In anthers (microsporangia) — meiosis in microspore mother cells produces haploid pollen grains.
In ovules (megasporangia inside the ovary) — meiosis in megaspore mother cells produces haploid megaspores.

Summary Table:

Plant	Site of Meiosis
Liverwort	Capsule (sporangium) of sporophyte
Moss	Capsule (sporangium) of sporophyte
Fern	Sporangia on sporophyte
Gymnosperm	Microsporangia & megasporangia (ovule)
Angiosperm	Anther (microsporangia) & ovule (megasporangia)

3Name three groups of plants that bear archegonia. Briefly describe the life cycle of any one of them.Show solution

Three groups of plants that bear archegonia:

Bryophytes (liverworts and mosses)
Pteridophytes (ferns and their allies)
Gymnosperms (e.g., Cycas, Pinus)

Life Cycle of a Moss (Bryophyte):

Step 1 – Dominant Gametophyte Generation:

The main plant body of a moss is the gametophyte (haploid, $n$ ).
It develops in two stages:
Protonema stage: The haploid spore germinates to form a creeping, green, branched filamentous structure called the protonema.
Leafy stage: Buds on the protonema develop into the erect, leafy gametophore bearing leaf-like and stem-like structures.

Step 2 – Sex Organs:

The gametophyte bears:
Antheridia (male sex organs) → produce biflagellate antherozoids (male gametes).
Archegonia (female sex organs) → each contains one egg cell (female gamete).

Step 3 – Fertilisation:

Water is essential for fertilisation.
Antherozoids swim to the archegonium and fuse with the egg to form a diploid zygote ( $2n$ ).

Step 4 – Sporophyte Generation:

The zygote develops into a multicellular sporophyte ( $2n$ ), which is partially or wholly dependent on the gametophyte.
The sporophyte consists of a foot, seta, and capsule.
Inside the capsule, spore mother cells undergo meiosis (reduction division) to produce haploid spores ( $n$ ).

Step 5 – Dispersal and Germination:

Spores are dispersed and germinate to form new protonema, completing the cycle.

$\text{Spore}(n) \xrightarrow{\text{germination}} \text{Protonema}(n) \rightarrow \text{Gametophyte}(n) \xrightarrow{\text{fertilisation}} \text{Zygote}(2n) \rightarrow \text{Sporophyte}(2n) \xrightarrow{\text{meiosis}} \text{Spores}(n)$

Conclusion: The life cycle shows alternation of generations with the dominant gametophytic phase.

4Mention the ploidy of the following: protonemal cell of a moss; primary endosperm nucleus in dicot; leaf cell of a moss; prothallus cell of a fern; gemma cell in Marchantia; meristem cell of monocot; ovum of a liverwort; and zygote of a fern.Show solution

Concept: Ploidy refers to the number of chromosome sets in a cell. Haploid ( $n$ ) cells belong to the gametophyte generation; diploid ( $2n$ ) cells belong to the sporophyte generation. The primary endosperm nucleus (PEN) is triploid ( $3n$ ) as it is formed by fusion of two polar nuclei ( $n + n$ ) with one male gamete ( $n$ ).

Structure	Generation	Ploidy
Protonemal cell of a moss	Gametophyte	Haploid ( $n$ )
Primary endosperm nucleus in dicot	— (formed after triple fusion)	Triploid ( $3n$ )
Leaf cell of a moss	Gametophyte	Haploid ( $n$ )
Prothallus cell of a fern	Gametophyte	Haploid ( $n$ )
*Gemma cell in Marchantia***	Gametophyte	Haploid ( $n$ )
Meristem cell of monocot	Sporophyte	Diploid ( $2n$ )
Ovum of a liverwort	Gametophyte (gamete)	Haploid ( $n$ )
Zygote of a fern	Beginning of sporophyte	Diploid ( $2n$ )

Key Explanations:

Protonema, leaf cells of moss, prothallus, gemma cells, and ovum are all part of the gametophyte → haploid ( $n$ ).
Meristem of monocot and zygote of fern are part of the sporophyte → diploid ( $2n$ ).
Primary endosperm nucleus = 2 polar nuclei ( $n$ each) + 1 male gamete ( $n$ ) = triploid ( $3n$ ).

5Write a note on economic importance of algae and gymnosperms.Show solution

Economic Importance of Algae:

(A) As Food:

Algae are the primary producers in aquatic ecosystems and form the base of the aquatic food chain.
Chlorella and Spirulina are used as food supplements rich in proteins.
Porphyra, Laminaria, and Sargassum are used as food in many parts of the world (especially East Asia).

(B) Commercial Products:

Agar-agar is obtained from red algae (Gelidium, Gracilaria) and is used in food industry, as a culture medium in microbiology, and in cosmetics.
Algin is obtained from brown algae and used as a thickening agent in ice creams, paints, and textiles.
Carrageenan from red algae is used as an emulsifying agent.

(C) Diatomite / Diatomaceous Earth:

Cell walls of diatoms (Bacillariophyceae) deposit silica and form diatomaceous earth, used in filtration of oils, syrups, and in insulation materials.

(D) Fertilisers:

Blue-green algae (Cyanobacteria) such as Nostoc and Anabaena fix atmospheric nitrogen and are used as biofertilisers in paddy fields.

(E) Fossil Fuels:

Fossil diatoms contribute to the formation of petroleum deposits.

Economic Importance of Gymnosperms:

(A) Timber:

Gymnosperms are a major source of softwood used in construction, furniture, and paper pulp.
Pinus, Cedrus (deodar), Abies provide commercially important timber.

(B) Resins and Turpentine:

Pinus species yield resin and turpentine oil, used in paints, varnishes, and medicines.

(C) Edible Products:

Seeds of Pinus gerardiana (chilgoza) are edible.
Seeds of Cycas are used as food after processing.

(D) Medicinal Uses:

Taxol, an anti-cancer drug, is obtained from Taxus (yew tree).
Ephedra yields ephedrine, used in treating asthma and bronchitis.

(E) Ornamental Plants:

Cycas, Thuja, Araucaria are widely used as ornamental plants in gardens.

(F) Sago:

Starchy food material sago is obtained from the pith of Cycas stem.

6Both gymnosperms and angiosperms bear seeds, then why are they classified separately?Show solution

Given: Both gymnosperms and angiosperms produce seeds, yet they are placed in separate groups.

Reason for Separate Classification:

Although both groups produce seeds, they differ fundamentally in the following ways:

Feature	Gymnosperms	Angiosperms
Ovule/Seed enclosure	Ovules are naked (not enclosed in an ovary); seeds remain exposed on the surface of megasporophylls	Ovules are enclosed within an ovary; seeds are enclosed within fruits
Flowers	Flowers are absent; reproductive structures are cones (strobili)	True flowers are present
Fruit formation	No fruit is formed	Ovary develops into a fruit after fertilisation
Endosperm	Endosperm is haploid (formed before fertilisation)	Endosperm is triploid (formed by double fertilisation)
Double fertilisation	Absent	Present
Vessels in xylem	Generally absent (except Gnetum)	Generally present
Companion cells	Absent in phloem	Present in phloem
Cotyledons	Many (polyembryony common)	One (monocots) or two (dicots)

Conclusion: The most fundamental difference is that in gymnosperms the ovules (and hence seeds) are naked (Greek: gymnos = naked, sperma = seed), while in angiosperms the ovules are enclosed within an ovary (Greek: angeion = vessel). This structural and reproductive difference justifies their separate classification.

7What is heterospory? Briefly comment on its significance. Give two examples.

Definition of Heterospory:

The phenomenon of producing two types of spores — morphologically and physiologically distinct — by a single plant is called heterospory.

Microspores — smaller spores that germinate to form the male gametophyte.
Megaspores — larger spores that germinate to form the female gametophyte.

This is in contrast to homospory, where all spores are of the same type and size.

Examples:

Selaginella (a pteridophyte)
Salvinia (a pteridophyte)
All gymnosperms and angiosperms are also heterosporous.

Significance of Heterospory:

Nutritional advantage: The megaspore is larger and contains more stored food, which nourishes the developing female gametophyte and embryo.

Reduction of gametophyte: Heterospory leads to the reduction of the gametophyte generation, which becomes increasingly dependent on the sporophyte — a trend seen in the evolution of higher plants.

Precursor to seed habit: Heterospory is considered a precursor to the seed habit. The retention of the megaspore within the megasporangium (as seen in Selaginella) is the first step towards the evolution of the ovule and seed.

Ensures cross-fertilisation: Since male and female gametophytes develop from different spores, it promotes cross-fertilisation and thus genetic variation.

Conclusion: Heterospory is an important evolutionary advancement that ultimately led to the development of seeds in higher plants.

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8Explain briefly the following terms with suitable examples:- (i) protonema (ii) antheridium (iii) archegonium (iv) diplontic (v) sporophyll (vi) isogamy

(i) Protonema:

Definition: The protonema is the first stage of the gametophyte in the life cycle of mosses. It develops directly from the germination of a haploid spore.
Structure: It is a creeping, green, branched, filamentous (thread-like) structure.
Function: It gives rise to buds which develop into the leafy gametophore (the mature gametophyte).
Example: Funaria (a common moss). The spore germinates to produce the protonema, which then develops into the leafy moss plant.

(ii) Antheridium:

Definition: The antheridium is the male sex organ (gametangium) found in bryophytes, pteridophytes, and some gymnosperms.
Structure: It is a club-shaped or spherical multicellular structure enclosed by a jacket of sterile cells.
Function: It produces male gametes (antherozoids/sperms), which are usually biflagellate and motile.
Example: In Funaria (moss), antheridia are borne at the tips of male branches. In ferns, antheridia are present on the prothallus.

(iii) Archegonium:

Definition: The archegonium is the female sex organ (gametangium) found in bryophytes, pteridophytes, and gymnosperms.
Structure: It is a flask-shaped multicellular structure consisting of a venter (swollen base containing the egg cell) and a neck (through which the male gamete travels).
Function: It produces and houses the egg cell (female gamete). After fertilisation, the zygote develops within the venter.
Example: In Marchantia (liverwort), archegonia are borne on archegoniophores. In ferns, archegonia are present on the prothallus.

(iv) Diplontic:

Definition: A diplontic life cycle is one in which the diploid sporophyte ( $2n$ ) is the dominant, photosynthetic, and independent phase of the life cycle. The gametophyte is highly reduced and represented by only a few cells.
Characteristic: Meiosis occurs during gamete formation (gametic meiosis). The gametes are the only haploid structures.
Example: All gymnosperms and angiosperms show a diplontic life cycle. In angiosperms, the pollen grain (male gametophyte) has only 2–3 cells and the female gametophyte (embryo sac) has only 7 cells/8 nuclei.

(v) Sporophyll:

Definition: A sporophyll is a leaf-like structure that bears sporangia (spore-producing structures).
Types:
Microsporophyll — bears microsporangia and produces microspores.
Megasporophyll — bears megasporangia and produces megaspores.
Arrangement: In gymnosperms, sporophylls are arranged spirally on an axis to form cones (strobili).
Example: In Pinus, microsporophylls form the male cone and megasporophylls form the female cone. In ferns, the fertile leaves bearing sporangia are also called sporophylls.

(vi) Isogamy:

Definition: Isogamy is a type of sexual reproduction in which the two fusing gametes are morphologically and physiologically identical (same size, shape, and structure). The gametes may be flagellated (motile) or non-flagellated.
Significance: It is considered the most primitive type of sexual reproduction.
Example:
In Ulothrix and Spirogyra (green algae), the fusing gametes are morphologically similar — this is isogamy.
In Chlamydomonas, some species show isogamy where both gametes are equal-sized and biflagellate.

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9Differentiate between the following:- (i) red algae and brown algae (ii) liverworts and moss (iii) homosporous and heterosporous pteridophyte

(i) Red Algae vs. Brown Algae:

Feature	Red Algae (Rhodophyceae)	Brown Algae (Phaeophyceae)
Pigments	Chlorophyll $a$ , $d$ ; phycoerythrin (red), phycocyanin	Chlorophyll $a$ , $c$ ; fucoxanthin (brown)
Colour	Red to purple	Olive green to dark brown
Stored food	Floridean starch	Mannitol and laminarin
Cell wall	Cellulose + phycocolloids (agar, carrageenan)	Cellulose + algin
Flagella	Absent (non-motile gametes in most)	Present; two unequal lateral flagella
Habitat	Mostly marine; found in deeper waters	Mostly marine; found in cooler regions
Plant body	Multicellular, complex thallus	Multicellular; ranges from simple to complex (e.g., Kelp)
Examples	Polysiphonia, Porphyra, Gracilaria, Gelidium	Ectocarpus, Fucus, Laminaria, Sargassum
Economic importance	Source of agar-agar	Source of algin; used as food

(ii) Liverworts vs. Mosses:

Feature	Liverworts	Mosses
Plant body	Thalloid, flat, dorsiventral, lobed (liver-shaped)	Leafy; upright, slender axes with spirally arranged leaf-like structures
Rhizoids	Unicellular, smooth-walled	Multicellular, with oblique cross walls
Protonema	Absent or poorly developed	Well-developed, filamentous (prominent stage)
Sporophyte	Simple; consists of foot, seta, and capsule; seta short	More elaborate; consists of foot, seta, and capsule; seta long
Elaters	Present in capsule (help in spore dispersal)	Absent; peristome teeth present
Vegetative reproduction	By gemmae in gemma cups (e.g., Marchantia)	By fragmentation and secondary protonema
Examples	Marchantia, Riccia, Pellia	Funaria, Sphagnum, Polytrichum

(iii) Homosporous vs. Heterosporous Pteridophytes:

Feature	Homosporous Pteridophytes	Heterosporous Pteridophytes
Type of spores	Produce one type of spore (all spores are morphologically similar)	Produce two types of spores — smaller microspores and larger megaspores
Gametophyte	A single type of gametophyte (bisexual prothallus) bearing both antheridia and archegonia	Two types of gametophytes — male gametophyte (from microspore) and female gametophyte (from megaspore)
Sporangia	Only one type of sporangium	Microsporangia (producing microspores) and megasporangia (producing megaspores)
Significance	More primitive condition	More advanced; considered a precursor to seed habit
Examples	Lycopodium, Equisetum, most ferns (Dryopteris)	Selaginella, Salvinia

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10Match the following (column I with column II): (a) Chlamydomonas — (i) Moss; (b) Cycas — (ii) Pteridophyte; (c) Selaginella — (iii) Algae; (d) Sphagnum — (iv) Gymnosperm

Matching:

Column I	Column II
(a) Chlamydomonas	(iii) Algae
(b) Cycas	(iv) Gymnosperm
(c) Selaginella	(ii) Pteridophyte
(d) Sphagnum	(i) Moss

Justification:

Chlamydomonas is a unicellular, biflagellate green alga (Chlorophyceae).
Cycas is a gymnosperm (class Cycadopsida) with pinnate leaves and large cones.
Selaginella is a pteridophyte (club moss) known for heterospory.
Sphagnum is a moss (bryophyte) also called peat moss, used as a fuel source.

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11Describe the important characteristics of gymnosperms.

Important Characteristics of Gymnosperms:

(1) Naked Seeds:

The most distinguishing feature is that the ovules are not enclosed within an ovary wall.
After fertilisation, the seeds remain exposed (naked) on the surface of megasporophylls.
The name 'gymnosperm' is derived from Greek: gymnos = naked, sperma = seed.

(2) Plant Body:

They are perennial, woody plants — mostly large trees or shrubs (e.g., Pinus, Cedrus).
Cycas has an unbranched trunk with a crown of large pinnate leaves.
Some are the tallest and oldest living organisms (e.g., Sequoia).

(3) Roots:

Possess tap root system.
In Cycas, coralloid roots are present which harbour nitrogen-fixing cyanobacteria (Anabaena, Nostoc).
In Pinus, roots have mycorrhizal association (fungal symbiosis).

(4) Leaves:

Leaves are well-adapted to withstand extremes of temperature, humidity, and wind.
In conifers, leaves are needle-like with a thick cuticle and sunken stomata to reduce water loss.
In Cycas, leaves are large and pinnate (like a palm).

(5) Heterospory:

Gymnosperms are heterosporous — they produce two types of spores:
Microspores (in microsporangia on microsporophylls)
Megaspores (in megasporangia/ovules on megasporophylls)

(6) Cones (Strobili):

Sporophylls are arranged spirally on an axis to form compact cones:
Male cones (microsporangiate strobili) bear microsporophylls.
Female cones (megasporangiate strobili) bear megasporophylls with ovules.

(7) Pollen Grains and Pollination:

Microspores develop into pollen grains (male gametophyte).
Pollination is anemophilous (by wind).
The pollen tube carries the male gametes to the archegonium in the ovule.

(8) Ovule and Fertilisation:

The ovule consists of the nucellus surrounded by integuments with a micropyle.
The megaspore mother cell undergoes meiosis to produce megaspores; one develops into the female gametophyte bearing archegonia.
Fertilisation occurs when the male gamete fuses with the egg in the archegonium → zygote ( $2n$ ).

(9) Endosperm:

Endosperm is haploid ( $n$ ) and is formed before fertilisation (pre-fertilisation endosperm).

(10) No Double Fertilisation:

Unlike angiosperms, gymnosperms do not show double fertilisation.

(11) Vascular Tissue:

Possess well-developed vascular tissue (xylem and phloem).
Xylem generally lacks vessels (except Gnetum); phloem lacks companion cells.

(12) Examples:

Cycas, Pinus, Cedrus, Abies, Ginkgo, Ephedra, Gnetum.

Conclusion: Gymnosperms represent an intermediate group between pteridophytes and angiosperms, characterised chiefly by naked seeds, heterospory, cone-bearing habit, and wind pollination.

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Frequently Asked Questions

What are the important topics in Plant Kingdom for CBSE Class 11 Biology?

Key topics in Plant Kingdom include Classification of Plants, Algae, Bryophytes, Pteridophytes. Study these first, then practise questions on each for Class 11 exams.

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