Classification of pteridophytes - class-XI

Genera like Selaginella and Salvinia which produce two kinds of spores, macro (large) and small (micro) spores are known as heterosporous. Microspore and macrospore germinate and gives rise to male and female gametophyte respectively. The female gametophytes in these plants are retained on the parent sporophyte for a variable period. The development of the zygote into young embryo takes place within the female gametophytes. This event is a precursor to the seed habits considered an important step in evolution. So, the correct answer is 'Embryo develops in female gametophyte which is retained on parent sporophyte'.

Selaginella is a pteridophyte also known as spike moss or little club moss. It is a tropical plant. It has world wide distribution. It grows in damp forests. Some species occur in temperate regions. They grow in moist shady places. In Selaginella male gametes are spindle shaped and biflagellate. Hence option D is correct.

Selaginella is a genus of primitive vascular plants in the family Selaginellaceae. Selaginella has a tendency to form seed because the retention and germination of single megaspore within megasporangium to form a female gametophyte led to the phenomenon of seed habit, a characteristic feature of spermatophytes.

Selaginella exhibits heterospory, endosporic development, reduced gametophytes, and strobilus formation, which are considered advanced evolutionary traits in pteridophytes.

Rudimentary seed habit means plants are reproducing sexually by seed but it is not fully developed. For e.g. in Selaginella female gametophytes are retained on the parent sporophytes for different periods. Within the female gametophytes, the development of the zygote into young embryos takes place. This event is a very important step in evolution as a precursor to seed habit. 

Selaginella is a classic example of a heterosporous pteridophyte, producing both microspores and megaspores.

Heterosporous pteridophytes (e.g., Selaginella) always produce dioecious gametophytes. A heterosporous life history occurs in some pteridophytes and in all seed plants. It is characterized by morphologically dissimilar spores produced from two types of sporangia: microspores, or male spores, and megaspores (macrospores), or female spores. In pteridophytes, megaspores are typically larger than microspores, but the opposite is true in most seed plants.

Prothallus is the self supporting haploid plant of the gametophytic generation and is concerned with sexual reproduction. Prothallus is generally monoecious and bears sex organs on the ventral side.

In selaginella, the sporangia near the apex of a vertically-held strobilus or along the upper side of a horizontally-held strobilus are darker in color and are oval. These contain many very tiny orange spores, the products of meiosis of several sporocytes. These nearly-microscopic spores are called microspores. This makes their sporangium a microsporangium and the sporophyll a microsporophyll. The microsporangia is yellowish brown in color.

The strobili of Selaginella or spike moss is heterosporous. It bears both microsporangium and megasporangium on the axis of the microsporophyll and megasporophyll respectively. The strobili with the sporophylls arranged look like a spike or a cone.

Selaginella rupestris or rock spike moss belongs to the family Selaginellaceae. The plant is heterosporous with the presence of both megaspores and microspores. However, the variation in sporangial distribution pattern in the strobili is related to the number of megaspores per megasporangium. More than often, the megasporangiate has only 1  megaspore per megasporangium.

• The sporangia produce spores by meiosis in spore mother cells. The spores germinate to give rise to inconspicuous, small but multicellular. free-living, mostly photosynthetic thalloid gametophytes called prothallus.
•  These gametophytes bear male and female sex organs called antheridia and archegonia, respectively. 
• The microspore germinates to form the male gametophyte. 
• The first unequal division (1-1) in a microspore results in the formation of a small lenticular prothallial cell (vegetative cell) and a large antheridial initial. The prothallial cell does not divide further. 
• Hence, prothallial cells in the male gametophyte of Selaginella is 1.
• So, the correct answer is '1'.
  

Rhizophores are leafless axial organs, which apices are the only sites for root formation  are unique to the Selaginella genus. Both rhizophores and roots are dichotomously branched, forming a multibranch rhizophore root system.

Selaginella lepidophylla is commonly known as the resurrection plant because it can survive extreme desiccation by curling up and rehydrating when water is available.

Heterospory is the production of two different types of spores by the sporophytes of land plants. Of all the options given in the question Selaginella, Pinus and Cycas all produce micorspores and megaspores for reproduction. However, Pteridium on the other hand is homosporous.

Pteridophytes are divided into four classes: Psilopsida, Lycopsida, Sphenopsida and Pteropsida. Selaginella belongs to Lycopsida. Selaginella has small leaves called microphylls. Sporophylls are compactly arranged into structures called strobili or cones. They are heterosporous as they produce two types of spores, macro (large) and micro (small).

A resurrection plant is any plant that can survive in dehydration conditions. Selaginella lepidophylla is known as resurrection plant. It is a plant species native to North America, Central and South America. The plant is also known as moss for bird's nest due to its appearance on dehydration. 

Selaginella is spike moss or club moss. Peat moss is Sphagnum (Bryophyte).

Pteridophytes are vascular plants. Leaves called sporophylls produce clusters of capsular structures called sporangia that bears spores which germinate and yield gametophytes. Hence they show alternation of generations, in which a sporophyte produces spores through meiosis and a gametophyte forms gametes by mitosis. 

The correct answer is 'Sphenopsida'

Option D is mismatched as the sporangia in selaginella contain four very large yellow spores. These four are the result of meiosis from a single sporocyte. The spores are called megaspores because of their large size. This makes the sporangium a megasporangium and the sporophyll a megasporophyll.

Azolla is extensively grown in rice paddies to increase rice production by more than to 50%. Nitrogen is the single most limiting factor in rice cultivation, strongly affecting the crop yield. Azolla substantially increases the amount of nitrogen fertiliser available to growing rice and it is has been used for thousands of years as a green nitrogen fertiliser to increase rice production.

The correct answer is 'lycopsida'

Pteropsida is the class that includes the true ferns.

Rhizophores is a  structure of controversial morphological nature.They are leafless and  positively geotropic organs that have localised origin and develop from angle meristems. Goebel and Bower considered them as Organs sui generis (i.e.,neither roots or shoots). According to J.C.Shoute,Organ sui generis is one that is a novelty and has not arisen as result of  metamorphosis of any organ.

Heteromorphic alternation of generation means a sporophytic phase and gametophytic phase alternate each other. Eg: Dryopteris

In Dryopteris sori, a group of sporangia covered with indusium are present along the margin of pinnae or leaflets. In it 2-8 sori are borne on the abaxial surface of the mature fronds (sporophylls). They are situated in two rows at the tips of the veinlets in between the midrib and the margins. The sori appear reniform due to the kidney shaped protective thin and membranous covering, called as indusium.

In Pteridophyte Dryopteris the gametophytes give rise to sporophyte by gametic union and sporophyte gives rise to gametophyte by forming haploid spores after meiosis. 

The multiflagellated antherozoids of Dryopteris, point out that they originated from aquatic ancestors. In auatic environment the multiflagellated antherozoids swim in the water and fertilize the egg. Water is necessary for the fertilisation process. It proves their aquatic ancestry.

The polycyclic condition is the most complex of stelar organization found among pteridophytes. It is a dictyostele consisting of two or more concentric rings of meristeles. It occurs in Pteridium sp. 

Young sporophyte of Pteris draws nourishment from the foot. Foot is formed first, which absorbs water, minerals from prothallus. Prothallium, or prothallus is usually the gametophyte stage in the life of a fern or other pteridophyte. The prothallium develops from a germinating spore. It is a short-lived and inconspicuous heart-shaped structure typically 2-5 millimeters wide, with a number of rhizoids (root-like hairs) growing underneath, and the sex organs: archegonium (female) and antheridium (male). Appearance varies quite a lot between species. Some are green and conduct photosynthesis, while others are colorless and nourish themselves underground as saprotrophs. 

Dryopteris species can be identified by the circular shaped sori, that is covered by a kidney-shaped, translucent tissue. It is called as indusium. It is a shield like outgrowth of the leaves.

The class Pteropsida is characterized by pteridophytic plants, that have large, dissected leaves and sporangia, that are borne on the leaves. Pteropsida is divided into three classes - (i) filicineae, (ii) gymnespermae, (iii) angiospermae. 

Some epidermal cells give rise uniseriate bicellular brown hairs on young leaves of Pteris or any other fern, called as ramenta. 

In the male gametophyte of Selaginella, the single prothallial cell is the only vegetative structure, as the rest of the cells develop into the antheridium.

The sperm of Selaginella are attracted to the archegonia by chemical substances, specifically malic acid, which is a common chemotactic agent in pteridophytes.

Dryopteris, is a genus with more than 250 species and is widespread in the temperate zones in northern hemisphere. The diploid sporophyte and haploid gametophyte of Dryopteris regularly alternate with each other. The haploid spore which gives rise to the gametophyte which is the monoecious prothallus and bears sex organs on its ventral side. After fertilization, they give rise to the sporophyte which is the dominant asexual member in the life cycle of the plant and is a perennial evergreen, differentiated into rhizome (stem), roots and leaves. Hence, both the gametophyte and sporophyte are independent of each other.

The archegonium of Selaginella is highly reduced and typically contains only one neck canal cell.

Microspores of Selaginella are very small, typically measuring around 15 micrometers in diameter.

The archegonium of Selaginella is more reduced than that of Funaria, featuring an embedded venter, absence of a stalk, and a very short neck.

In Dryopteris the opening mechanism of sporangium is effectively operated by stomium. Stomium is formed of the thin-walled cells, marking the line or region of dehiscence of a fern sporangium. It is the opening in an anther, usually between lip cells through which dehiscence occurs.

In the stem of Selaginella, the endodermal cells are elongated and form bridge-like structures called trabeculae that connect the stele to the cortex.

The neck of the archegonium in Selaginella is very short, consisting of two tiers of four cells each.

In Selaginella, the development of the male gametophyte is endosporic, meaning it occurs entirely within the microspore wall.

The megaspore of Selaginella germinates to produce the female prothallus, which bears the archegonia.

The 13-celled male gametophyte of Selaginella consists of 1 prothallial cell and a 12-celled antheridium.

Selaginella is characterized by heterospory and the presence of ligules on its leaves.

In Selaginella, the megasporophyll bears the megasporangium, which is functionally analogous to the carpel in angiosperms that encloses the ovule. This comparison highlights the evolutionary trend toward seed-bearing structures.

The male gametophyte of Selaginella is highly reduced. It consists of a single prothallial cell and an antheridium.

Like all pteridophytes, the life cycle of Selaginella exhibits alternation of generations where the sporophyte is the dominant, independent, and photosynthetic phase.

The stem of Selaginella typically contains a protostele, which is the simplest type of stele consisting of a solid core of xylem surrounded by phloem.

The plant body of Selaginella is a sporophyte, which is diploid and produces spores through meiosis.

Selaginella bryopteris is widely identified as the plant known as Sanjeevani in Indian traditional medicine due to its resurrection properties.

Selaginella is considered to show a rudimentary seed habit because the megaspore is retained within the megasporangium and the female gametophyte develops while still attached to the parent plant.

The ligule is a small, scale-like outgrowth found on the adaxial surface of the leaves of Selaginella, which is a characteristic feature of the order Selaginellales.

Selaginella can reproduce vegetatively through various methods including fragmentation, tubers, and resting buds, which allow it to propagate effectively.

Heteromorphic alternation of generations refers to a life cycle where the sporophyte and gametophyte phases are morphologically distinct, which is characteristic of Selaginella.

The male gametes (antherozoids) of Selaginella are biflagellate, meaning they have two flagella to aid in swimming toward the archegonia.

Selaginella is known to possess pyrenoids in its chloroplasts, which is a unique feature among many pteridophytes.

Chemotaxis is the movement shown by organism in the direction of the external chemical stimuli. In Selaginella, sperm sense the chemoattractant and orient its swimming towards the archegnonia. Chemotropism is the growth movement shown by organism in the direction of the external chemical stimuli. Chemonasty is the nastic movement shown by organism in response to the external chemical stimuli. Spermatozoa can sense this chemoattractant and orient their swimming direction up the concentration gradient towards the egg cell located in the venter of archegonia

Heterosporous pteridophytes produce two types of spores (microspores and megaspores). Selaginella and Salvinia are classic examples of heterospory.

In S. bryopteris and S. lepidophylla, megaspores are retained inside the megasporangium (not megasporogonium, which appears to be a typographical error in the question) for germination. This retention of megaspores is a step toward seed habit and occurs in specific Selaginella species. The other species pairs listed are known to release megaspores externally.

The folding of lamina in bud condition is called as ptyxis. Arrangement of leaves on the stem branches is called as phyllotaxy. Vernation is the phenomenon of arrangement of leaves in the bud. 

Selaginella is a tracheophyte that exhibits heterophylly (different leaf sizes), lacks companion cells (typical of pteridophytes), and has vessels in its xylem, which is an advanced trait.

Selaginella is heterosporous, meaning it produces two types of spores. Therefore, it does not exhibit homospory.

Lycopsida is a class of Pteridophyta, not Bryophyta. Bryophyta includes classes like Hepaticopsida, Anthocerotopsida, and Bryopsida.

S. rupestris is known for having uniform leaves, exhibiting homophylly, whereas most other Selaginella species are heterophyllous.

Heterospory is the production of two distinct types of spores, namely microspores and megaspores. Plants such as Selaginella and Marsilea exhibit heterospory and bear sporangia that produce these two different types of spores.

Because Selaginella has both microspores and megaspores, the plant is called as heterosporous. The other fern-allies are homosporous (having only one type/size of spore). This significance of this advance in evolution is important because sexual dimorphism is being expressed much earlier in the life cycle. The organisms to appeared next this are all heterosporous.

A resurrection plant is any poikilohydric plant that can survive extreme dehydration, even over months or years. Selaginella lepidophylla, is known as resurrection plant or birds nest moss as it shows ball like appearance (cespitose habit) in dry season. It is a plant species native to North America, Central and South America, and sold as a novelty.

Heterospory means the production of two spores of different sizes and of two different development patterns. Small spore is called microspore and large spore is called megaspore. Microspore produces the male gametophyte that possesses male sex organs while megaspore produces the female gametophyte that possesses female sex organs. It ultimately leads to seed development. For example, Selaginella, Salvinia, Azolla. Dryopteris and Adiantum are homosporous and haploid spores are produced in each sporangium. 

In Selaginella, trabeculae are endodermal in nature as they develop from the endodermis. In Marsilea, they are cortical. 'soetes' appears to be a typo (likely for 'isoetes'), where trabeculae are sporogenous. In Funaria (moss), trabeculae are amphithecial in nature, developing from the amphithecium layer of the sporangium wall.

The matching of groups to their characteristics is: Psilopsida (rootless), Lycopsida (sporangiophore), Sphenopsida (companion cells - though this is debatable, it is the provided key), and Pteropsida (megaphyllous leaf).

• Spore is uninucleate haploid spherical structure.
• The spore germinates into gametophyte known as prothallus.
• Prothallus has archegonia present on the ventral side.
• Hence, the Prothallus of Dryopteris is a Gametophyte.  It bears archegonia on the ventral side. 
• So, the correct answer is 'Gametophyte, ventral'.

In the life cycle of Dryopteris, the asexual sporophyte is the dominant individual. This is perennial and evergreen and differentiates into rhizome (stem), roots and leaves ( fronds). When the fronds mature these become fertile and are called as sporophylls since they contain sori. In each sorus stalked sporangia is present arising from the placenta, the swollen outgrowth on the divisions of the pinna or leaflets.

The archegonium which develops from a single superficial cell of prothallus is the archegonial initial found just back of the apical meristem. The archegonia  are sessile and embedded. The archegonial initially divides to give 4+4 cells which make up the neck. The neck has a single neck canal cell.

Strobilus is called the fertile branch, because it bears the reproductive structures such as microsporophylls and megasporophylls.

In Dryopteris, the neck consists of a wall or jacket layer of 4 vertical rows of sterile neck cells. The neck cells enclose a central neck canal. They contains a single, long neck canal cells with two nuclei.

In older plants, the branches bear reproductive structures at their tips. They are called as strobilus or spondiferous spike. The arrangement of micro and megasporophylls in the strobili of different species is variable. The strobili of S.oregana are among the longest in the flora and they often show several novel features. In S.kraussiana, there is only one megasporangium at the base and the rest of the sporophylls bear microsporangia.

Selaginella and Salvinia are considered the first plants to exhibit a significant step toward the evolution of seed habit because embryo develops in female gametophyte which is retained on parent sporophyte. It occurs because Selaginella and Salvinia both are heterosporous, i.e., these plants produce two kinds of spores, macro (large) and micro (small) spores. In the heterosporous species, the female gametophyte remains on the parent sporophytes for variable periods. The development of the zygotes into young embryos takes place within the female gametophytes. This event is a precursor to the seed habit (tendency towards seed formation) considered an important step in evolution. Hence, heterospory leads to seed habits in plants.

The presence of Ligule - a small tongue shaped appendage on the adaxial side of the leaf near the leaf base is a distinctive feature of the Selaginella. This consists of elongated secretory cells the glossopodium which tends to keep the sporangium wet. Another distinctive feature is the cones or strobilus on which the sporophylls are present.

Dryopteris Filix-mas (Linn.) is commonly known as male-shield fern, because they have a shield-shaped protective covering for their spore containing structures. 

Heterospory is a phenomenon in which two kinds of spores are borne by the same plant. These spores differ in size. The smaller one is known as microspore and the larger one is known as megaspore. The microspore germinates to form the male gametophyte and the megaspore germinates to form the female gametophyte. Heterospory evolved first in pteridophytes such as Selaginella and Salvinia. Hence option B is correct.

Under dry conditions, the xerophytic species of Selaginella roll into brown balls but remain uprooted. This phenomenon is called as a cespitose habit. But during moist conditions, the brown balls become green and unroll again. Therefore, these plants are called as resurrection plants. e.g. Selaginella lepidophylla and Selaginella bryopteris.

Peritichious flagellation is found in Escherichia coli where the flagella are projecting in all directions;
The living fossil plant is the Ginkgo biloba.Largest perennial alga is the Macrocystis pyrifera.
Smallest flowering plant is Wolffia arrhiza and belongs to the genus WolffiaRhizophore - the downward-growing leafless dichotomous shoots is a characteristic feature of the genus Selaginella. Thus, the correct answer is option D.

Selaginella bryopteris, known commonly as sanjeevini and sanjivani booti. It is used medicinally in India. The rare life saving herb Sanjeevani known to have been brought by Lord Hanuman to save Lord Laxman. The Hindu mythology Sanjeevani is described as a magical plant which can wake dead people to the life, or which lends immortality. In the high, hostile peaks of the Himalayas where sustaining life is a challenge in itself, scientists say they have found a wonder herb that can regulate the immune system, help adapt to the mountain environment and, above all, protect from radioactivity.

In majority of the pteridophytes, all the spores are of similar kinds, such plants are called as homosporous. Genera like Selaginella and Salvinia which produce two kinds of spores, macro (large) and micro (small) spores, are known as heterosporous. The megaspores and microspores germinate and give rise to female and male gametophytes, respectively. The female, gametophytes in these plants are retained on the parent sporophytes for variable periods. The development of the zygotes into young embryos take place within the female gametophytes. This event is a precursor to the seed habit considered an important step in evolution.

The antherozoid of Lycopodium is pear shaped with two flagella at the anterior end. The biflagellate antherozoids of Lycopodium resemble more to the antherozoids of Bryophytes, rather than those of vascular plants.

Peritrichous flagellation means having flagella projecting in all directions (e.g., E. coli). 

The megaspores and microspores germinate and give rise to female and male gametophytes, respectively. The female gametophytes in these plants are retained on the parent sporophytes for variable periods. The development of the zygotes into young embryos take place within the female gametophytes. 

Selaginella rupestris is xerophytic plant known as resurrection plant or birds nest moss as it shows ball like appearence in dry season.

The main plant body of SelagineIla sp. is sporophyte which is diploid in condition.

The four megaspores derived from a megaspore mother cell may not always be functional. i.e. In S.rupestris single megaspore is functional.

The retention of the megaspore and the development of the embryo within the female gametophyte, which remains attached to the parent sporophyte, is a crucial evolutionary step toward the seed habit.

In Dryopteris, on the lowerside of the leaflet an outgrowth is present. It consists of a stalk like placenta and a flap, that protects group of sporangia. This is called as true indusium.

In Dryopteris, the annulus and the stomium help in the dehiscence of the sporangium and dispersal of spores. At maturity, the sporangium dehisces by drying action, which exerts pressure on mouth assisted by shrinkage of the annulus. Lastly mouth of sporangium open and spores are liberated.

Gametophytes have sessile jacketed multicellular sex organs. The male is antheridium and female is archegonium. Antheridia form biflagellated (Selaginella, Lycopodium) or multiflagellated (Dryopteris) male gametes. Antheridium producing about 32 anthropoids. Each anthropoid is large antinuclear coiled and multi flagellate.

A resurrection plant is any plant that can survive extreme dehydration and desiccation for years. Selaginella lepidophylla is a  a plant species that is native to America. It is an example of resurrection plant.

In mosses (bryophytes), the sporophyte is dependent on the gametophyte. In pteridophytes (like Selaginella/Ferns), the sporophyte is independent.

Selaginella is the primary example of a heterosporous pteridophyte belonging to the class Lycopsida.