📘 NEET Notes (Pteridophyta)

PTERIDOPHYTA

Term Pteridophyta was proposed by Haeckel. The study of pteridophytes is known as pteridology.
Pteridophytes are known as “reptiles of plant kingdom.”
General features
In pteridophyta main plant body is sporophytic.
The plant body is completely differentiated into true root, stem and leaves.
The primary root remains alive for a short period; after some time it is replaced by adventitious roots.
Stem may be erect or prostrate. In some pteridophytes stem is underground, called a rhizome.
On the basis of leaves, pteridophytes are of two types –
- First: stem larger and leaves smaller → microphyllous pteridophytes (e.g., Equisetum, Lycopodium, Selaginella).
- Second: stem smaller while leaves larger → macrophyllous pteridophytes (e.g., Pteridium, Pteris, Marsilea – most ferns).
Note: Differentiation in plant body starts from bryophytes.

Specific Features

Most pteridophytes are found in moist soil and shady places; some are aquatic (Marsilea, Salvinia, Azolla, Isoetes).
They are not completely successful terrestrial plants because they need water for fertilization, so they prefer shady and moist places.
Pteridophytes are also called vascular cryptogames → they are vascular plants (xylem and phloem present).
In pteridophytes, vessels in xylem and companion cells in phloem are absent.
- Exception: xylem of Pteridium, Selaginella, Marsilea contains false vessels (formed by modification of tracheids).
Vascular bundle types: concentric, amphicribal (hadrocentric), mesarch, and closed.
Secondary growth is absent (due to absence of cambium), but exceptionally present in stem of Isoetes.
Pteridophytes are called the first successful terrestrial plants → more adapted than bryophytes.
Some pteridophytes are epiphytes (e.g., Lycopodium phlegmeria, Ophioglossum pendulum, Pleopeltis).

🌿 Pteridophyta – Specific Features & Vascular Details

Most pteridophytes occur in moist soil and shady places.
Some pteridophytes are aquatic: Marsilea, Salvinia, Azolla, Isoetes.
Pteridophytes are not fully successful terrestrial plants → they need water for fertilization (sperm motility).
Therefore, they prefer shady and moist habitats.
Pteridophytes are called vascular cryptogams because they:
- Lack flowers and seeds (cryptogams = hidden reproductive organs).
- Possess vascular tissues (xylem and phloem).

In pteridophytes:

Vessels in xylem are absent.
Companion cells in phloem are absent.
Exception: Xylem of Pteridium, Selaginella, Marsilea contains false vessels (formed by modification of tracheids).
Vascular bundles:
- Concentric type.
- Amphicribal (hadrocentric).
- Mesarch condition.
- Closed (no cambium).
Secondary growth:
- Absent in most pteridophytes (due to absence of cambium).
- Exception: Present in the stem of Isoetes.
Evolutionary position:
- Pteridophytes are regarded as the first successful terrestrial plants → more adapted than bryophytes.
Habit variations:
- Some pteridophytes are epiphytes (grow on other plants) → examples: Lycopodium phlegmeria, Ophioglossum pendulum, Pleopeltis.

🌿 Section 3: Life Cycle of Pteridophytes

Main plant body = sporophyte (diploid).
Sporophyte is differentiated into root, stem, and leaves.
Sporophyte bears sporangia (on sporophylls).
Sporangia produce spores by meiosis (hence spores are haploid).
Pteridophytes are therefore sporophyte-dominant plants.
Spores germinate to produce the gametophyte.
The gametophyte is called a prothallus.
Prothallus is multicellular, green, autotrophic, haploid.
Prothallus is independent (unlike angiosperms, where gametophytes are reduced).
Antheridia (male sex organs) and archegonia (female sex organs) are present on the gametophyte.
Antheridia → produce antherozoids (sperm) which are motile, multiciliate.
Archegonia → produce egg cells.

Fertilization:

Needs external water.
Male gametes swim in water to reach archegonia.
Fertilization occurs, producing zygote (2n).
Zygote develops into embryo, then into sporophyte.
Thus alternation of generations is heteromorphic:
- Dominant sporophyte
- Small, short-lived gametophyte
Pteridophytes are homosporous or heterosporous:
- Homosporous → produce only one type of spore (e.g., Psilotum, Lycopodium).
- Heterosporous → produce two kinds of spores:
  - Microspores (male gametophyte)
  - Megaspores (female gametophyte)
  - Examples: Selaginella, Salvinia, Marsilea, Azolla
Importance of heterospory:
- Evolutionary precursor of the seed habit.

🌿 Section 4: Classification of Pteridophytes

🔹 Class I – Psilopsida

Example: Psilotum.
Oldest and simplest pteridophytes.
Stem: dichotomously branched, aerial, green.
Leaves: absent or very small enations (not true leaves).
Roots: true roots absent, instead rhizoids are present.
Sporangia:
- Three sporangia fuse to form a synangium.
Homosporous.

🔹 Class II – Lycopsida

Examples: Lycopodium (club moss), Selaginella (spike moss).
Leaves: microphyllous (small, with single vein).
Stem: prostrate or erect, branched.
Roots: adventitious.
Sporangia:
- Produced in axils of sporophylls.
- Sporophylls may form compact strobilus (cone).
Lycopodium: homosporous.
Selaginella: heterosporous (produces microspores + megaspores).

🔹 Class III – Sphenopsida

Example: Equisetum (horse tail).
Stem: jointed with ridges and furrows, silica present in epidermis.
Branches: whorled.
Leaves: microphyllous, arranged in whorls, scale-like.
Roots: adventitious.
Sporangia:
- Produced on sporangiophores grouped into strobili.
Homosporous.

🔹 Class IV – Pteropsida (Filicinae)

Examples: Pteris, Dryopteris, Adiantum (maiden hair fern), Marsilea.
Stem: rhizome (usually underground).
Leaves: large, pinnately compound (macrophyllous).
Young leaves: show circinate vernation (coiled).
Roots: adventitious.
Sporangia:
- Borne in groups called sori (singular: sorus) on ventral surface of leaves.
- Each sorus may be covered by indusium (thin membranous cover).
Most are homosporous.
Some aquatic members (Marsilea, Salvinia, Azolla) are heterosporous.

🌿 Section 5: Special Features, Exceptions & Importance

Heterospory in Pteridophytes

Some genera like Selaginella, Salvinia, Marsilea, Azolla produce two types of spores → microspores (male gametophyte) and megaspores (female gametophyte).
Heterospory represents a significant evolutionary step → precursor to the seed habit.

Seed Habit Evolution

In heterosporous pteridophytes:
- Female gametophyte develops inside the megaspore (retained within sporangium).
- This resembles seed plants, where female gametophyte is retained in ovule.
Selaginella shows the beginning of seed habit evolution.

Sporophyte vs Gametophyte

Sporophyte is dominant, independent, differentiated into root, stem, leaves.
Gametophyte is small, short-lived, photosynthetic prothallus.

Independent Gametophyte

Unlike seed plants, the gametophyte in most pteridophytes is free-living.
Exception: in heterosporous pteridophytes, the female gametophyte is endosporic (develops inside megaspore).

Sexual Organs

Antheridia → male, produce motile, multiciliate sperms.
Archegonia → female, flask-shaped, contain egg.

Fertilization

Water–dependent (requires a film of water).
Male gametes swim to archegonia to reach egg.

Embryo Formation

Zygote → embryo → new sporophyte (next generation).

Alternation of Generations

Heteromorphic:
- Large, dominant sporophyte.
- Small, short-lived gametophyte.

Economic Importance

Azolla: used as biofertilizer (symbiotic association with nitrogen-fixing Anabaena).
Equisetum: stems used for cleaning utensils (due to silica).
Ferns (Pteris, Adiantum): ornamental.
Fossil pteridophytes (like Lepidodendron) → contributed to coal deposits.

Practice Questions

Q1. Assertion (A): Pteridophytes are called vascular cryptogams.
Reason (R): They possess well-developed xylem and phloem, but lack seeds.
(a) A and R true, R explains A
(b) A and R true, R does not explain A
(c) A true, R false
(d) A false, R true
Answer: (a)

Q2. A: In most pteridophytes, sporophyte is the dominant phase.
R: The main plant body is diploid and independent.
(a) A and R true, R explains A
(b) A and R true, R does not explain A
(c) A true, R false
(d) Both false
Answer: (a)

Q3. A: Pteridophyte gametophyte (prothallus) is vascular and autotrophic.
R: It develops exosporically in soil.
(a) A and R true, R explains A
(b) A true, R false
(c) A false, R true
(d) Both false
Answer: (b)

Q4. A: Selaginella shows seed habit.
R: In Selaginella, female gametophyte is retained on sporophyte and embryo develops in situ.
(a) A and R true, R explains A
(b) A and R true, R does not explain A
(c) A true, R false
(d) Both false
Answer: (a)

Q5. A: All pteridophytes are homosporous.
R: Spores in pteridophytes are always identical in size.
(a) A and R true
(b) A true, R false
(c) A false, R true
(d) Both false
Answer: (c)

Q6. A: Development of sporangia in Adiantum is leptosporangiate.
R: Each sporangium originates from a group of initial cells.
(a) A and R true, R explains A
(b) A and R true, R does not explain A
(c) A true, R false
(d) A false, R true
Answer: (c)

Q7. A: Isoetes exhibits secondary growth.
R: Cambium is present in its stem.
(a) A and R true, R explains A
(b) A and R true, R does not explain A
(c) A true, R false
(d) A false, R true
Answer: (a)

Q8. A: Sporophylls in ferns are photosynthetic.
R: In ferns, sporophylls and tropophylls are morphologically different.
(a) A and R true, R explains A
(b) A and R true, R does not explain A
(c) A true, R false
(d) Both false
Answer: (c)

Q9. A: Pteridophytes are dependent on water for fertilization.
R: Antherozoids are motile and reach archegonia via water.
(a) A and R true, R explains A
(b) A and R true, R does not explain A
(c) A true, R false
(d) Both false
Answer: (a)

Q10. A: In Lycopodium, sporophylls are scattered along the stem.
R: Sporangia develop in compact strobili at the tips of stem.
(a) A and R true, R explains A
(b) A true, R false
(c) A false, R true
(d) Both false
Answer: (c)

Q11. Statement I: Pteridophytes are the first vascular plants to colonize land successfully because they possess true roots, stems, and leaves.
Statement II: They are completely independent of water for fertilization due to the presence of pollen tubes.
(a) Both statements are correct
(b) Both statements are incorrect
(c) Statement I correct, II incorrect
(d) Statement I incorrect, II correct
Answer: (c)

Q12. Statement I: In homosporous pteridophytes like Lycopodium, all spores are identical in size and germinate into a bisexual gametophyte.
Statement II: In Selaginella, microspores and megaspores develop into unisexual male and female gametophytes, respectively.
(a) Both statements are correct
(b) Both statements are incorrect
(c) Statement I correct, II incorrect
(d) Statement I incorrect, II correct
Answer: (a)

Q13. Statement I: The sporophyte of Psilotum lacks true roots and leaves, which is due to evolutionary reduction rather than primitiveness.
Statement II: The body of Psilotum shows dichotomous branching and enations that function as leaves.
(a) Both statements are correct
(b) Both statements are incorrect
(c) Statement I correct, II incorrect
(d) Statement I incorrect, II correct
Answer: (a)

Q14. Statement I: In leptosporangiate ferns like Adiantum, each sporangium develops from a single initial cell and produces a limited number of spores.
Statement II: In eusporangiate types such as Equisetum, sporangia arise from a group of initial cells and are massive, producing a large number of spores.
(a) Both statements are correct
(b) Both statements are incorrect
(c) Statement I correct, II incorrect
(d) Statement I incorrect, II correct
Answer: (a)

Q15. Statement I: The deposition of silica in the epidermis of Equisetum provides mechanical strength and resistance.
Statement II: Due to silica, Equisetum is called “scouring rush” and was used for polishing metals.
(a) Both statements are correct
(b) Both statements are incorrect
(c) Statement I correct, II incorrect
(d) Statement I incorrect, II correct
Answer: (a)

Q16. Statement I: Isoetes is unique among pteridophytes because it shows secondary growth by a true vascular cambium.
Statement II: In most pteridophytes, vascular cambium is absent and secondary growth does not occur.
(a) Both statements are correct
(b) Both statements are incorrect
(c) Statement I correct, II incorrect
(d) Statement I incorrect, II correct
Answer: (a)

Q17. Statement I: In Lycopodium, the sporophylls are arranged in compact strobili and each sporophyll bears a sporangium in its axil.
Statement II: Lycopodium is heterosporous because it produces both microspores and megaspores in the same strobilus.
(a) Both statements are correct
(b) Both statements are incorrect
(c) Statement I correct, II incorrect
(d) Statement I incorrect, II correct
Answer: (c)

Q18. Statement I: Fertilization in pteridophytes requires free water because antherozoids are motile and need to swim to the egg.
Statement II: This dependency restricts their habitat mainly to moist and shaded environments.
(a) Both statements are correct
(b) Both statements are incorrect
(c) Statement I correct, II incorrect
(d) Statement I incorrect, II correct
Answer: (a)

Q19. Statement I: The gametophyte of pteridophytes is free-living, photosynthetic, and haploid.
Statement II: In heterosporous pteridophytes, gametophytes are endosporic and reduced in size.
(a) Both statements are correct
(b) Both statements are incorrect
(c) Statement I correct, II incorrect
(d) Statement I incorrect, II correct
Answer: (a)

Q20. Statement I: In ferns, sori are groups of sporangia often covered by an indusium, which protects them during development.
Statement II: In Lycopodium, sporangia are also organized into sori beneath an indusium.
(a) Both statements are correct
(b) Both statements are incorrect
(c) Statement I correct, II incorrect
(d) Statement I incorrect, II correct
Answer: (c)

Q21. Refer to the following statement(s) and identify the group of plant which is being described:
(i) The sporophyte is the dominant plant body, differentiated into true roots, stems and leaves.
(ii) Leaves are microphylls with a single unbranched vein.
(iii) The sporophylls form compact strobili, each bearing a sporangium in its axil.
(iv) They are homosporous plants but some species show mycorrhizal gametophytes.
(a) Ferns
(b) Lycopodium
(c) Psilotum
(d) Equisetum
Answer: (b)

Q22. Refer to the following statement(s) and identify the plant which is being described:
(i) The stem is ribbed, jointed and bears nodes and internodes.
(ii) Whorls of branches arise from the nodes and the epidermis is impregnated with silica.
(iii) The strobili consist of peltate sporangiophores bearing multiple sporangia.
(iv) Spores are homosporous and bear hygroscopic elaters.
(a) Psilotum
(b) Equisetum
(c) Selaginella
(d) Isoetes
Answer: (b)

Q23. Refer to the following statement(s) and identify the group of plant which is being described:
(i) They are called “living fossils” because of resemblance to early vascular plants.
(ii) They have dichotomously branched green stems.
(iii) True roots and leaves are absent, but rhizoids and enations are present.
(iv) They reproduce by homosporous spores.
(a) Selaginella
(b) Psilotum
(c) Lycopodium
(d) Ferns
Answer: (b)

Q24. Refer to the following statement(s) and identify the group of plant which is being described:
(i) They possess small leaves (microphylls) with ligules.
(ii) They show heterospory, producing both microspores and megaspores.
(iii) Female gametophyte develops endosporically within the megaspore wall.
(iv) This condition is regarded as an incipient seed habit.
(a) Selaginella
(b) Lycopodium
(c) Isoetes
(d) Equisetum
Answer: (a)

Q25. Refer to the following statement(s) and identify the plant group which is being described:
(i) They have large compound leaves called fronds.
(ii) The young leaves show circinate vernation.
(iii) Sporangia are grouped into sori, often covered by an indusium.
(iv) Their gametophyte is a free-living, heart-shaped green prothallus.
(a) Ferns (Pteropsida)
(b) Lycopsida
(c) Psilopsida
(d) Sphenopsida
Answer: (a)

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Complete Notes: Pteridophyte (NEET Biology)