Plant Kingdom Test 7

A pteridophyte is a vascular plant (with xylem and phloem) that disperses spores. Because pteridophytes produce neither flowers nor seeds, they are also referred to as "cryptogams", meaning that their means of reproduction is hidden.

The seed habit was established in Gymnosperms. The development of seed habit, seen in present-day gymnosperms (and also in angiosperms) eliminated the requirement of water during sexual reproduction. In seed plants, two types of sporangia develop on sporophylls. They are known as megasporangium (ovule) and microsporangium.  The ovule upon fertilization gives rise to the seed.  

Most conspicuous alternation of generation occurs in Pteridophyta. This means that a diploid generation (the sporophyte, which produces spores) is followed by a haploid generation (the gametophyte or prothallus, which produces gametes). Pteridophytes differ from mosses and seed plants in that both generations are independent and free-living, although the sporophyte is generally much larger and more conspicuous. Hence option C is correct.

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.

Sporophyte characteristic of Psilopsida is rhizoids, some are without leaves and protostele. In Psilopsida, plants have rootless sporophytes. The stem is differentiated into an underground rhizome and an aerial part. Both are dichotomously branched. The rhizome bears rhizoids, both perform the function of a root. The aerial branches are green, leafless and bear small veinless outgrowths and carry out photosynthesis.
So, the correct answer is option D.

In Lycopsida, the sporophyte is differentiated into stem, roots and leaves. The leaves are microphyllous and with a single vein. The vascular strands or steles may be protostelic, siphonostele or polystelic. The leaf-gaps are always absent, sporophylls produce a single sporangium on the adaxial side near its base. The sporophylls are borne in strobili. They are homosporous or heterosporous. The antherozoids are biflagellate or multiciliated.
Therefore, the correct answer is option A.

The Ophioglossum is named as  "Adder's-tongue fern" because the tall stalk that bears its spores is thought to resemble a snake's tongue. An indicator of ancient meadows, it can be found mainly in southern England. 

The branching of roots involves the endogenous origin of new root apical meristems in the pericycle or, in many ferns (e.g. Marsilea ), the endodermis of the parent root.Roots arise from the embryonic axis, from other roots or stems; the latter is where all roots originate in non‐seed vascular plants.

From algae to bryophyta, there is absent of vascular tissue while the plants from pteridophyta to angiosperms has vascular tissue for water conduction.

In Pteridophyta there is a regular feature of alternation of generations. At the time of sporogenesis the reduction division takes place and the haploid spores are formed, which represent the first stage of the gametophyte generation. Later on fertilization takes place and a zygote is produced, which represents the first stage of sporophyte generation. This way the gametophyte gives rise to the sporophyte by the process of syngamy and the sporophyte gives rise to the gametophyte by the process of meiosis.

Seed plants and mosses, the life cycle of pteridophytes involves alternation of generations. This means that a diploid generation (the sporophyte, which produces spores) is followed by a haploid generation (the gametophyte or prothallus, which produces gametes).

The cryptogams are flowerless and seedless plants. They are simple plants like algae, mosses and ferns which do not produce flowers, fruits and seeds. Cryptogams are considered as lower plants.

Cone bearing Pteridophyta are Lycopsida and Sphenopsida.
Pteridophytes (Gr. pteron= feather, phyton = plant) constitute the most primitive seedless vascular plants that reproduce by means of spores.
They have 4 sub-divisions:
(i) Psilopsida (Psilopsids)
(ii) Lycopsida (Clubmosses),
(iii) Sphenopsida (Horsetails) and
(iv) Pteropsida(Ferns).

Lycopsida:
1. Plant body more advanced and shows differentiation into root, stem and leaves.
2. Leaves are microphyllous (small) having a single unbranched vein in the midrib region.
3. Sporangia are borne in the axil of the fertile leaves (sporophyils).
4. Sporophyll form compact strobili (singularstrobilus). e.g., Lycopodium, Selaginella.

Sphenopsida:
1. Plant body still more advanced and shows differentiation into nodes and internodes like higher vascular plants.
2. Leaves microphyllous, and arise in whorls at each node.
3. Sporangia develop on sporangiophores which form compact cones at the apex of fertile branches (e.g., Equisetum).

Adiantum caudatum or the maidenhair fern is also known as  the "walking fern" . This is because its new plantlets grow wherever the arching leaves of the parent plant touch the ground, creating a walking effect. Shaded areas is its habitat. This is an ornamental fern found in south-east countries such as Bangladesh, Burma, India, Nepal, Philippines, Thailand and  China.

A pteridophyte is a vascular plant (with xylem and phloem) that disperses spores. The pteridophytes include the ferns, horsetails, and the lycophytes (clubmosses, spikemosses, and quillworts). These are not a monophyletic group because ferns and horsetails are more closely related to seed plants than to the lycophytes.

Selaginella is the only living genus of the order Selaginellales and is commonly known as 'spike moss' or 'small club moss'. It is a large genus comprising of about 700 species distributed all over the world. Abundantly it is found growing in tropical rain forests.

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.

Azolla (mosquito fern, duckweed fern, fairy moss, water fern) is a genus of seven species of aquatic ferns in the family Salviniaceae. They are extremely reduced in form and specialized, looking nothing like other typical ferns but more resembling duckweed or some mosses.Fertile leaves bear spore-producing sporangia, which are typically organized in groups, called sori. Usually sori are on the lower side of the leaf, and some groups have specialized structures associated with their sporangia and sori. ferns, sporangia are formed from a group of cells, which is the plesiomorphic state.

Fern belongs to Pteropsida. The antheridia of Pteropsida are slightly projected on the surface. They are spherical or oval in shape. Each antheridium has a layer of jacket cells. Antherozoid mother cells are present within the jacket. Sperm mother cells are changed in spirally twisted multiflagellate sperm or antherozoids.

These cells undergo meiosis to form haploid spores. If a spore lands on a suitable site, it will germinate and grow via mitosis into a mature gametophyte plant. A gametophyte is the plant that produces gametes. The fern gametophyte is a small (approximately 5 mm), bisexual, heart-shaped plant called a prothallus.

Isoetes commonly known as the quillworts, is a genus of plants in the class Isoetopsida and order Isoetales. They are lycopods. Generally in pteridophytes, when the young organs mature, no further growth in diameter takes place. In several extinct groups a special ring of cells, the cambium, produced additional xylem to the inside and phloem cells to the outside (secondary growth as opposed to primary growth achieved by apical activity of the stem and root), resulting in increased diameter and a truly woody plant. This is common in many seed plants today, but in the extant pteridophytes only two genera (Botrychium and Isoetes) show a slight vestige of secondary growth.

In pteridophytes, the main plant body is a sporophyte which is differentiated into true root, stem and leaves. The leaves in pteridophyta are small (microphylls) as in Selaginelia or large (macrophylls) as in ferns. The sporophytes bear sporangia that are subtended by leaf-like appendages called sporophylls.

Selaginella is the only living genus of the order Selaginellales and is commonly known as 'spike moss' or 'small club moss'. It is a large genus comprising of about 700 species distributed all over the world. Abundantly it is found growing in tropical rain forests

Sanjeevani has close relationship with Selaginella brayopteris.In many research Silaginella brayopteris showed the quality of Sanjeevani but scientists have not cleared yet that Selaginella brayopteris is Sanjeevani.

Nostoc in Azolla is used to increase the yield of paddy crop because it can supply the crop with nitrogen because nitrogen is the single most limiting factor in paddy cultivation.

In Fern, the antheridia and archegonia are developed on prothallus. The antherozoid and archegonia fuse to form diploid zygote, which is the beginning of the sporophytic stage. The sporophyte (2n) gives rise to gametophyte (n), i.e., prothallus and again by the process of union of the gametes the sporophytic stage is developed. Thus, it may be said that fern exhibits an alternation of haploid (gametophytic) and diploid (sporophytic) generations. However, unlike Bryophytes, the fern plant is the diploid sporophyte.

Correct Answer :- D

Explanation : Non flowering plants or non seed producing plants or spore producing plants in the plant kingdom are called Cryptogams. Algae, Bryophytes and pteridophytes together called Cryptogams. These are present on aquatic and terrestrial places.

Presence of motile stage in life cycle & requirement of water as a medium to complete life cycle is diagnostic characters of Cryptogams.

The origin and evolution of the seed habit was started in late Devonian times about 385 M. a) The earliest seed plants, “progymnosperms”, emerged in the late Devonian . Progymnoperm fossils show vegetative morphologies to seed plants.

The leaves of Fern are also known as fronds. The frond of fern is a pinnately compound leaf and has its origin in a small outgrowth on the stem near its growing point. The petiole of the leaf ends in a long rachis, which bears pinnae. In young leaves, both the rachis and petiole are covered with small, brown hairy scales, called as Ramenta. The young leaves are circinate, and they uncoil like a watch spring as they grow. The mature leaves last only for one season and again ten to twenty leaves come out, which remain spirally arranged on the rhizome.