Pteridophytes (General) Questions in English

(B) The correct answer is $B$. Pteridophytes are known as 'vascular cryptogams'.
The term 'cryptogams' is derived from two Greek words: $Kryptos$ (hidden) and $gamos$ (marriage/wedded).
These plants reproduce by means of spores and do not produce seeds or flowers.
They are the first terrestrial plants to possess vascular tissues ($xylem$ and $phloem$).

(D) Heterospory is a condition where two different types of spores,namely microspores and megaspores,are produced by the same plant.
$Selaginella$,$Isoetes$,and $Marsilea$ are all examples of pteridophytes that exhibit heterospory.
Therefore,the correct answer is all the above.

(B) Heterospory is a phenomenon in which a plant produces two different types of spores that differ in size and function.
These are known as microspores (small,male) and megaspores (large,female).
This condition is a significant evolutionary step towards the seed habit in plants,commonly observed in Pteridophytes like $Selaginella$ and $Salvinia$.

(B) In the plant kingdom,the life cycle involves an alternation of generations between a haploid gametophyte and a diploid sporophyte.
In $Algae$ and $Fungi$,the dominant phase is haploid $(n)$.
In $Mosses$ (Bryophytes),the gametophyte is the dominant,independent,and photosynthetic phase.
In $Ferns$ (Pteridophytes),the sporophyte is the dominant,independent,and photosynthetic phase,which is diploid $(2n)$. Therefore,the diploid stage is dominant in $Ferns$.

(A) In the life cycle of a fern,the sporophyte produces spores through meiosis,which are haploid $(n)$.
These haploid spores germinate to form a small,multicellular,free-living,photosynthetic thalloid structure called the prothallus.
Since the prothallus develops directly from a haploid spore,it is also haploid $(n)$.

(C) Most ferns are homosporous,meaning they produce only one type of spores. These spores germinate to form a prothallus,which is a bisexual gametophyte. While some ferns exhibit heterospory,the characteristic feature of the majority of ferns is homospory. Seed bearing is a characteristic of gymnosperms and angiosperms. Ferns possess tracheids but lack vessels in their xylem.

(C) The main plant body of pteridophytes is a sporophyte,which is diploid $(2n)$.
This sporophyte is the dominant,independent,and photosynthetic phase in their life cycle.
The gametophytic phase is small,inconspicuous,and often short-lived.

(D) The term "Botanical snake" refers to the genus $Ophioglossum$, which belongs to the group $Pteridophytes$.
This name is given because the leaves (fronds) of $Ophioglossum$ resemble the hood of a black cobra snake.

(B) Heterosporous pteridophytes (e.g.,$Isoetes$,$Selaginella$,$Marsilea$,etc.) produce two types of spores: microspores and megaspores.
Microspores germinate to form male gametophytes,and megaspores germinate to form female gametophytes.
Since the male and female gametophytes are separate,they are referred to as dioecious gametophytes.
The development of the gametophyte is endosporic,meaning it occurs within the spore wall.

(D) In many pteridophytes (like $Selaginella$ and $Equisetum$) and gymnosperms (like $Pinus$),the sporophylls (spore-bearing leaves) are arranged spirally along an axis to form distinct,compact,cone-like structures.
These structures are known as strobili or cones.
Therefore,the correct option is $D$.

(C) The condition in which a plant produces two distinct types of spores,known as megaspores and microspores,is called $Heterospory$. In such plants,these spores are produced in two different types of sporangia,namely megasporangia and microsporangia. This is a significant evolutionary step observed in certain pteridophytes like $Selaginella$ and $Salvinia$.

(D) Pteridophytes are the first terrestrial plants to possess vascular tissues ($xylem$ and $phloem$).
They are $cryptogams$,meaning they do not produce flowers or seeds.
Since they do not produce flowers,they also do not produce fruits.
Therefore,all the given statements are correct characteristics of Pteridophytes.

(B) The main independent plant body of a pteridophyte is the $Sporophyte$.
It is differentiated into true roots,true stem,and true leaves.

(A) The prothallus is the gametophyte of a fern.
It is exosporic,flat,green,autotrophic,cordate $(heart-shaped)$,multicellular,short-lived,small,reduced,dorsiventral,and a free-living independent non-vascular structure.

(A) $Cooksonia$ and $Rhynia$ of the $Psilophytales$ group are the oldest known fossilized vascular pteridophytes on land.

(D) $Rhynia$ is a well-known fossil pteridophyte that existed during the $Silurian$ and $Devonian$ periods. It is considered one of the simplest and most primitive vascular plants known to science.

(D) $Azolla$ and $Salvinia$ are true aquatic ferns.
$Azolla$ is used as a biofertilizer because it contains the nitrogen-fixing cyanobacterium $Anabaena$ in its leaves.
$Salvinia$ is an aquatic weed and is commonly known as the 'Sorrow of Kashmir'.

(B) The plant group that possesses vascular tissues ($xylem$ and $phloem$) but does not produce seeds is known as $Pteridophytes$.
$1$. Bryophytes lack true vascular tissues.
$2$. Gymnosperms and Angiosperms are seed-bearing plants (Spermatophytes).
$3$. Pteridophytes reproduce via spores and are the first terrestrial plants to possess vascular tissues.

(A) The seed habit is an evolutionary process that leads to the development of seeds.
It was first observed in certain pteridophytes,such as $Selaginella$ and $Marsilea$.
These plants exhibit heterospory (production of two types of spores) and the retention of the megaspore within the parent plant,which are the essential precursors to the development of a seed habit.

(A) $Ginkgo$ is a $Gymnosperm$,not a $Pteridophyte$.
$Selaginella$,$Polypodium$,and $Azolla$ are all examples of $Pteridophytes$.

(C) The correct answer is $C$. Pteridophytes,along with $Cycadofilicales$,are considered the chief coal-forming plants.
The era of great coal-forming forests belongs to the $Carboniferous$ period.
Coal deposits found in India primarily belong to the $Permian$ period.

(C) The correct answer is $C$. Ferns (Pteridophytes) are considered the most primitive living vascular plants because they possess true vascular tissues ($xylem$ and $phloem$) but do not produce seeds or flowers. They represent the first group of plants to evolve a vascular system for the conduction of water and nutrients.

(A) The fern prothallus is a heart-shaped,photosynthetic,independent gametophyte. It is monoecious or homothallic because it bears both male sex organs (antheridia) and female sex organs (archegonia) on the same thallus.

(D) In ferns,the leaves that bear sporangia are known as sporophylls. These leaves are often referred to as fronds. The sporangia are typically arranged in clusters called sori on the dorsal or ventral surface of these sporophylls. Examples include $Pteris$ and $Dryopteris$.

(D) $Ramenta$ are thin,brown,chaffy,scale-like,or hairy structures found on the surface of the stem,petiole,and young leaves of ferns. They serve a protective function for the developing juvenile leaves against desiccation and mechanical injury.

(A) Ferns are pteridophytes,which reproduce via spores and do not produce seeds or flowers.
Fertilization in ferns requires water for the motile,flagellated sperms to swim towards the archegonia,which contain the egg.
Pollen tubes are characteristic of seed-bearing plants (gymnosperms and angiosperms) and are not involved in the fertilization process of ferns.

(A) The stele in most ferns is a $Dictyostele$.
$Dictyostele$ is a type of $Siphonostele$ that is perforated by several overlapping leaf gaps.
Each separate vascular strand in a $Dictyostele$ is referred to as a $meristele$.
Examples of plants with a $Dictyostele$ include $Dryopteris$,$Pteridium$,and $Pteris$.

(B) In the life cycle of ferns,the main plant body is a sporophyte $(2n)$.
It produces spores through meiosis within the sporangia.
Since these spores are produced via meiosis,they are haploid $(n)$.
These haploid spores germinate to form the prothallus,which is the independent gametophytic stage of the fern.
Therefore,the spore represents the beginning of the gametophytic stage.

(C) In eusporangiate development,the sporangium originates from a group of superficial initial cells.
These initial cells divide periclinally to form an outer wall layer and an inner sporogenous tissue.
This is in contrast to leptosporangiate development,where the sporangium arises from a single initial cell.

(D) Meristeles are small,vascular bundles found in the rhizomes of ferns.
Each meristele consists of a central xylem core surrounded by phloem,which is further enclosed by a pericycle and an endodermis.
These structures are characteristic of the complex vascular anatomy seen in the rhizomes of many Pteridophytes,particularly ferns.

(D) Apogamy: It is the development of a sporophyte directly from the gametophyte (prothallus) without the fusion of gametes (fertilization). In ferns,the prothallus is haploid,and if a sporophyte develops from its cells,it is an example of apogamy.

(D) The leaves (fronds) of ferns typically exhibit open dichotomous venation.
In this type of venation,the veins branch into two equal parts repeatedly (dichotomously) and do not form a network or closed loops.
This is a primitive and characteristic feature of pteridophytes like ferns,often referred to as furcate venation.

(B) Sorus $(sori = \text{plural})$: It is a cluster or group of sporangia that are attached to a specialized structure called the placenta on the underside of fern fronds, often protected by a membrane known as the indusium.

(A) The main plant body of pteridophytes,such as ferns,is a sporophyte $(2n)$.
These plants reproduce asexually by producing spores within specialized structures called sporangia.
The sporangia are often borne on the underside of leaves known as sporophylls.
Therefore,the correct answer is $A$ (Sporangium).

(D) The fern prothallus is the gametophytic stage in the life cycle of a fern.
In the life cycle of pteridophytes,the main plant body is a sporophyte $(2n)$,which produces spores through meiosis.
These spores germinate to form a small,multicellular,free-living,photosynthetic thalloid structure called the prothallus.
Since the prothallus is the gametophyte,it is haploid $(n)$ in nature.
Therefore,the cells of the fern prothallus contain a nucleus with $n$ chromosomes.

(B) The correct answer is $B$.
In ferns,the sporangium wall consists of a specialized row of cells called the $Annulus$.
As the $Annulus$ cells lose water through evaporation,they undergo tension,which causes the sporangium to rupture at the $Stomium$.
This mechanism acts like a sling,resulting in the forceful ejection of spores into the air for dispersal.

(B) In ferns,the sporangia are produced in clusters known as sori. These sori are typically found on the abaxial (under) surface of the leaves,which are referred to as sporophylls. They can be arranged marginally or superficially on the lower surface of the leaf.

(D) The prothallus of a fern is a flat,green,autotrophic,cordate $(heart-shaped)$,multicellular,short-lived,dorsiventral,and free-living independent gametophyte.
It typically measures about $1/8$ to $1/3$ inch $(5-10 \text{ mm})$ in size and lacks vascular tissues.

(D) The antherozoids of ferns are spirally coiled ($2-3$ coils) and multiflagellate,possessing $40-50$ whiplash-type flagella. Therefore,since they are coiled and multiflagellate,option $D$ is the most appropriate choice as it encompasses the characteristics described.

(A) In ferns,each sporangium consists of a multicellular stalk and a biconvex capsule. The capsule is the part that contains the spores.

(C) The $Stomium$ is a specialized region of the sporangium wall consisting of thin-walled,radially elongated cells.
When the sporangium matures and dries,the $Annulus$ (a row of thick-walled cells) contracts,causing the $Stomium$ to rupture or burst open,thereby releasing the spores.
Therefore,the $Stomium$ acts as the site of dehiscence for the sporangium.

(B) The leaves of ferns are large,megaphyllous,and feather-like,which are commonly referred to as fronds. The young,coiled leaves of ferns are specifically known as fiddleheads or circinate vernation,but the mature leaf structure is termed a frond.

(C) In ferns,the life cycle involves an alternation of generations. The diploid sporophyte produces haploid spores through meiosis within sporangia. When these spores land on a suitable substrate,they germinate to form a small,heart-shaped,independent,photosynthetic gametophyte known as the prothallus. Therefore,the prothallus develops directly from the spore.

(C) Ferns belong to the group Pteridophyta.
In Pteridophytes,the male gametes (antherozoids or sperms) are typically multiflagellated (multiciliate) and spirally coiled.
These sperms require water for fertilization to reach the archegonia.
Therefore,the correct description of a fern sperm is multiciliate and coiled.

(C) The dominant phase in the life cycle of a fern is the sporophyte.
In Pteridophytes,the main plant body is differentiated into true roots,stems,and leaves,and it represents the diploid $(2n)$ sporophytic generation.

(C) In most common ferns (leptosporangiate ferns),the number of spores per sporangium is typically $64$.
This occurs because the spore mother cell undergoes meiosis to produce $4$ spores,and the resulting cells undergo $4$ successive mitotic divisions ($2^4 = 16$ cells),followed by meiosis to produce $16 \times 4 = 64$ spores.
Therefore,$64$ is the characteristic number of spores found in the sporangium of many ferns.

(B) $Nephrolepis$ is a genus of ferns,which belong to the group $Pteridophyta$.
$Pteridophytes$ are vascular plants that reproduce via spores and have neither seeds nor flowers.
Therefore,the correct classification for $Nephrolepis$ is $Pteridophyte$.

(B) The antheridium in ferns (Pteridophytes) is a globose structure.
It consists of a central mass of androgonial cells surrounded by a sterile jacket layer.
This jacket layer is single-layered and is composed of exactly $3$ cells (two ring cells and one cap cell).

(D) . Ferns are generally the first colonizers of a burnt-down forest area.
This occurs because their underground $Rhizomes$ survive the fire,while the above-ground parts are destroyed.

(C) In ferns,the gametophyte stage is represented by a small,free-living,photosynthetic,heart-shaped structure called a prothallus.
This prothallus is monoecious,meaning it bears both male sex organs (antheridia) and female sex organs (archegonia) on the same plant body.
Therefore,the prothallus is bisexual.