SHORT QUESTIONS OF PTERIDOPHYTA
1. Give occurrence of pteridophytes.
Ans: Pteridophyta is a group of ancient plants. They formed the dominant part of the earths during Palaeozoic and Mesozoic periods. Majority of Pteridophytes became extinct. They are
preserved in the form of fossils or coal deposits. Only a few living Pteridophyta are left.
2. Differentiate between Microphyllous and Megaphyllous.
Ans: The sporophytes with small and scale like leaves are called. The sporophytes with large and prominent leaves is megaphyllous.
3. Differentiate between phyllosporous and stachyosporous Sporangia.
Ans: When the sporangia are borne on the leaves then the condition is known as phyllosporous. When sporangia borne in the axils of the leaves then the condition is known as stachyosporous.
4. What is tapetum? Give its function.
Ans: or two peripheral layers persist for the nourishment of the developing spores. These nourishing cells form tapetum.
5. Give alternation of generation in pteridophytes.
Ans: Pteridophyta show a regular alternation of sporophytic and gametophytic generations. The sporophytic stage is dominant. They have separate and independent gametophytic stage. Haploid spore is the beginning point of the gametophytic stage. Diploid oospore is the beginning point of the sporophyte.
6. What is Protostele?
Ans: The xylem is in the form of a solid mass in Protostele. It forms the central core of the stele. It is completely surrounded by the phloem. Pericycle and endodermis surrounds the phloem.
7. Differentiate between Haplostele and Actinostlele.
Ans: The protostele in which xylem core is smooth and rounded is called Haplostele. The protostele in which xylem core is star like is called Actinostlele.
8. What is plectostele?
Ans: In plectostele xylem forms several plates. These plates lie parallel to each other among the phloem elements. The protoxylem lies at the tips of the xylem plates or on one side.
9. What is Dictysotele?
Ans: This is a type or siphonostele in which different gaps overlap with each other. In this case, several gaps are present at a particular level.
10. Differentiate between Protoxylem and Metaxylem?
Ans: In case of protoxylem, the tracheids are annular with spiral thickening. Those tracheids elongates even after maturity. In case of Metaxylem, the thickenings on tracheids are scalariform in the form simple pits. They do not elongate after maturity.
11. What are Exarch, Mesarch and Endarch?
Ans: In case of exarch, protoxylem is lying on the periphery of metaxylem. In case of mesarch, protoxylem is lying in the middle of metaxylem. In case of endarch, the protoxylem is lying towards the inner side of the metaxylem.
12. What is rhizome? Give its function.
Ans: Rhizome is underground part of stem. Leaves and roots are absent on rhizome. Rhizome develops rhizoids for absorption of water.
13. How fertilization occur in Psiletum?
Ans: The neck canal cells of mature archegonium disintegrate. It produces a pore through which antherozoids enter the archegonium. Only one antherozoid fuses with the oosphere to produce oospore.
14. Give alternation of generation in Psilotum.
Ans: Psilotum shows regular alternation generations. The vegetative plant is sporophyte. It produces haploid spores by meioses. Spores germinate to give rise to the prothallus or gametophyte. The prothallus produces antheridia and archegonia. Fertilization produces diploid oospore. Oospore gives rise to the sporophyte. Thus sporophyte and gametophyte alternates with each other.
15. What are trabecullae?
Ans: The stele is separated from the cortex by a wide air space. These spaces have long radiating cells called trabeculea.
16. What is octant? Which structure does it give rise?
Ans: The embryonal cell divides to form eight cells or octants. Two cells of the octants divide more rapidly. They produce an outgrowth called foot on one side. Foot is the chief food absorbing organ of the developing embryo.
17. Give two evolutionary significance of Selaginella.
Ans: The production of gametes, fertilization and the development of the embryo, take place on the sporophyte. Megaspore is never released from the sporophyte. Selaginellq is heterosporous. The microspore produces the male gametophyte. It completes its development within the wall of the spore.
18. Differentiate between fertile and sterile branches of Equistem.
Ans: Fertile branches are short and brownish in colour. They are without lateral branches. Each fertile branch produces a cone or strobilus at the apex. The fertile branches are produced in the spring. These branches die after the production of cones. The sterile branches are green. These branches have numerous lateral branches. Sterile branches persist throughout the year.
19. Give internal structure of leaf of Equisetum?
Ans: Each mature root has a single layered epidermis. Cortex is composed of parenchymatous cells. Two layers of endodermis are present below the cortex. Cells of the inner layer of endodermis give rise to the secondary branches of the root. A definite pericycle is absent in roots. Stele is present in the centre. It is without pith.
20. Give process of fertilization in Equisetum.
Ans: The ventral canal cell and the neck canal cell of mature archegonia disintegrate. It forms passage for the antherozoids. Several antherozoids enter the archegonia. But only one of them fuses with the egg. The fertilized oosphere develops a wall and becomes the oospore.
21. Give structure of compound leaf of Adiantum.
Ans: Adiantum has large bipinnately compound leaves. The main axis of the leaf is called the rachis. The leaflets of the first order are called pinnae and leaflets of the second order are called as pinnules. Each leaflet is green and triangular.
22. What is circinate vernation?
Ans: The young leaves are coiled inward in the embryonic state. It is called circinnate vernation.
23. Give the walls of spores of Adiantum.
Ans: Each spore has a three layered wall. The outermost layer is perenitun or epispore. The inner most is endosporium or intine. The middle layer is thicker and it called exine or exosporium.
24. How does fertilization occur in Adiantum?
Ans: The antheridia and archegonia of the same thallus mature at different times. So cross fertilization takes place. The antherozoids are chemotactically attracted towards archegonia. Several antherozoids enter the archegonium but only one of them fuses with the oosphere to form oospore.
25. Give occurrence and common species of Marsilea.
Ans: Marsilea is an aquatic or semi aquatic plant. It is common in the temperate regions. It grow in fresh water ponds and ditches in Punjab. Marsilea quadrifolia and Marsilea minuta are commonly found in Pakistan.
26. What is sporocarp?
Ans: Both types of sporangia are found within the same sorus. The son i are produced in hard fruit-bodies called sporocarps.
27. Give occurrence of Polypodium.
Ans: Polypodium is a perennial herb. It is found mostly in temperate regions. It has worldwide distribution. Mostly is attached to some rocks. But some forms are epiphytic.
28. Give structure of archegonium of Polypodium.
Ans: The archegonia are also very numerous. Their neck is sunken in the prothellus. Each archegonium is flask shaped. It consists of curved neck and a venter. Neck is made up of several neck cells and one neck canal cells. Venter has single venter canal cell and oosphere.
29. Give alternation of generation in Polypodium.
Ans: Polypodium shows a regular alternation of sporophytic and gametophytic generations. Both generations are independent. Sporophyte produces the haploid spores by meiosis. The spores germinate to form haploid prothallus or gametophyte. Prothellus is monoecious. It produces antheridia and archegonia. The union of antherozoid and oosphere produces diploid oospore. Oospore germinates to form diploid sporophyte.