Q.1. Describe the characteristic features of Pteridophytes. (2002)
Ans. The plants of pteridophyta have following characters :
1. Pteridophytes are herbaceous shrubs with sporophytic plant body.
2. Plant body differentiated into root, stem and leaves.
3. Usually grow in moist and shady places, some members may be aquatic or xerophytic.
4. The leaves are small and sessile or scaly or large, petiolate and compound.
5. On the basis of leaf structure pteridophytes are of two types -
(i) Microphyllous, (ii) Megaphyllous.
6. The vascular tissues have xylem and phloem.
7. Xylem tissue is without vessels and phloem without companion cells.
8. spores may be similar (homosporus) or dissimilar (heterosporous).
9. The sporophytes reproduces by spore formation.
10. The spores are produces in sporangia.
11. Sporangia may produced on leaves and aggregate to form strobilus or cone.
12. The male sex organs is antheridium and female sex organs is archegonia.
13. Antherozoids are biflagellated or multiflagellated and motile.
14. Fussion takes place between egg cell and antherozoid result in the formation of a zygote.
15. Zygotes develops a new sporophytic plant.
16. They show Heteromorphic alternation of generation.
Q.2. Comment Upon : Pteridophyta is connecting link between Bryophata and Gymnosperm.
(2011, 12)
Related Question -
Q. Describe any four difference between Pteridophyta and Gymnosperm. (2008)
Q. Explain Pteridophyta is link of Bryophyta and Gymnosperm. (2004)
Q. Describe the affinities and dissimilarities of Pteridophytes from Bryophytes.
Ans. Affinities of Pteridophytes: -
The position of Pteridophyta is between Bryophyta and Spermatophyta. Therefore, they show similarities of both groups.
Resemblance with Gymnosperms: -
1. Plant body differentiated into well developed root, stem and leaves.
2. Sporophytic plant body.
3. Occurrence of circinate vernation.
4. Presence of vascular system.
5. Xylem has no vessels and phloem has devoid of companion cell.
6. Arrangement of sporangia in groups.
7. Formation of micro and megaspore in micro and Megasporangia.
8. Sporophytic generation long independent and dominant while gametophytic generation is short and dependent on sporophytic generation.
9. Suspensor formation common.
10. Same alternation of generation.
11. The spores many be homosporous or heterosporous.
Difference between Pteridophytes and Gymnosperms
Resemblance with Bryophyta: -
1. Terrestrial mode of life in both.
2. Both groups of gametophyte are thalloid.
3. Sporophyte varied.
4. Water medium is essential for fertilization.
5. Amphibious in nature.
6. presence of sterile jacket around sex organs
7. Sporogonium resembles simple rootless and leafless sporophytes of Psilophyta.
8. Presence of heterologous type of alternation of generation.
9. Sex organs are multicellular.
Difference between Pteridophyta and Bryophyta: -
On the basis of above mentioned similarities and diversities it can be said that Pteridophyta is a link between Bryophyta and Gymnosperm.
Q.3. Give the most acceptable classification of pteridophytes and their characters.
Ans. The classification of Pteridophytes proposed by Tippo (1942), which mostly accepted by the scientist, are as follows -
Sub Phylum 1. Psilopsida:-
Characters:-
1. Oldest and simplest vascular plant.
2. Presence of rhizoids on the erect and upright of shoot.
3. The sporophyte plant body is rootless.
4. Dichotomously branched aerial shoot.
5. Apical sporangia.
6. The stem show cylindrical or lobed protostele.
Example. Rhynia, Psilotum.
Sub-Phylum 2. Lycopsida:
Characters:-
1. The plant body is sporophyte.
2. Developed during Devonian of Paleozoic.
3. Plant body differentiated in root, stem, leaves.
4. Leaves bearing sporangia called sporophylls.
5. Sporophylls usually form cone (strobilli).
6. Sporaniga borne on abaxial surface.
7. The spores may be homo or heterospores,
8. The antherozoids are biciliate.
Example- Lycopodium or Selaginella.
Sub Phylum -3. Sphenopsida:-
Characters:-
1. Plant body is differentiated into leaf, root and stem.
2. Stem has nodes and internodes.
3. Leaves small and scaly.
4. Leaves arranged in whorls.
5. Sporangia develop on special stalled structure called spoangiophore,
6. Sporangia are closely packed together to form compact strobili.
Example . Equisetum.
Sub - Phylum 4. Pteropsida:
Characters: -
1. Dominant plant body sporophytic.
2. Plant body well differentiated into root, stem and leaves.
3. Leaves megaphylles and pinnatetly compound.
4. Sporangia develops on groups called sori.
5. Sori develops on the ventral surface of sporophylls.
6. Sporangia development may be leptosporangiate and eusporangiate.
7. Fertilization takes place with the help of water.
8. It shows well defined alternation of generation.
Example - Dryopteris, Pteris, Marsilea sand Azolla etc.
Q.4. Give an account of vegetative propagation in Pteridophytes.
Ans. Various methods of vegetative propagations are known in pteridophytes. In some it is very common and results in gregarious habit of plants. Some important methods are as follows:
1. Fragmentation: - The dichotomously branched plant body breaks into pieces. Each fragment under favourable conditions grows into a new plant e.g., Lycopodium, Selaginella rupestris.
2. Gemmae: - Multicellular bodies arise on the tip of stem (Lycopodium selago) on the rhizome (Psilotum nudum) on detachment they develop into new plants.
3. Death and Decay of Older Parts of Stem: -
Sometimes death and decay of older parts results in separation of young branches. Each branch can grow further to form a new plant, e.g., Lycopodium inundatum.
4. Bulbils: - These are dormant buds formed over the roots or leaves. Protocorm like capable of forming new plants. e.g., Lycopodium cernuum, Selaginella rupestris.
5. Resting Buds: - Formed under unfavourable conditions. In Lycopodium inundatum the whole plant body except apical tip dies during severe cold. The apical tip regenerates under favourable conditions.
6. Root Tubereles: - In Lycopodium cernuum roots bear swollen tubercles. These tubercles have the capacity to germinate and produce new plants.