NEET Plant Kingdom Previous Year Questions with Solutions

In bryophytes and pteridophytes, gametophytes exist as independent free-living individuals (such as moss gametophores or fern prothalli). In gymnosperms and angiosperms, however, the gametophytes are highly reduced and lack independent existence. The male gametophyte (pollen grain) develops inside the microsporangium, and the female gametophyte is permanently retained inside the megasporangium (nucellus) on the sporophyte.

• • NCERT Plant Kingdom: "Unlike bryophytes and pteridophytes, in gymnosperms the male and the female gametophytes do not have an independent free-living existence. They remain within the sporangia retained on the sporophytes."

Gymnosperms (from Greek: gymnos = naked, sperma = seed) are seed-bearing tracheophytes where the ovules are exposed on megasporophylls and not enclosed inside an ovary wall, both before and after fertilisation. Consequently, the seeds that develop are "naked" (not enclosed inside a fruit).

• • Angiosperms differ because their seeds are enclosed inside fruits.

Both Statement I and Statement II are canonically accurate according to standard plant morphology and taxonomy.

• • Matches official NTA final answer key Option A / (1).

Pteridophytes are vascular cryptogams possessing xylem and phloem, exhibiting alternation of generations with a dominant sporophytic phase. They are subdivided into four distinct taxonomic classes based on vegetative and reproductive morphology.

• • First terrestrial plants to possess vascular tissues.

Members of class Sphenopsida (commonly called horsetails or scouring rushes) feature articulated, jointed stems with distinct nodes and internodes, whorls of scale leaves at nodes, silica-impregnated epidermal cell walls, and compact strobili/cones at branch apices.

• • Possess ribbed stems with vallecular and carinal canals.

Bryophytes are non-vascular plants divided into liverworts and mosses. Gymnosperms are naked-seeded phanerogams (Conifers, Cycads, Ginkgo). Angiosperms are flowering plants (Monocots, Dicots). Sphenopsida belongs solely to pteridophytes.

• • Matches official NTA final answer key Option D / (4).

In pteridophytes, the main plant body is a diploid sporophyte differentiated into true root, stem, and leaves:

• • Sporophylls bear sporangia containing diploid spore mother cells (SMCs).
• • SMCs undergo reduction division (Meiosis in spore mother cells - Stage B) to produce haploid spores.

Development of the independent, photosynthetic gametophytic generation:

• • Haploid spores germinate to produce inconspicuous, small, multicellular, free-living, mostly photosynthetic thalloid gametophytes called the Prothallus stage (Stage A).
• • The prothallus bears male and female sex organs: antheridia and archegonia (Stage D).

Completion of the sexual cycle:

• • Water is required for the transfer of flagellated male gametes (antherozoids) released from antheridia to the archegonium (Stage E).
• • Fusion of an antherozoid with the egg present in the archegonium results in Fertilisation (Stage C).
• • The resulting zygote produces a multicellular, well-differentiated sporophyte, restarting the cycle.

Ordering the stages: B (Meiosis) -> A (Prothallus) -> D (Archegonia & Antheridia formation) -> E (Transfer of antherozoids in water) -> C (Fertilisation).

In bryophytes (mosses and liverworts), the dominant, independent, photosynthetic stage is the haploid gametophyte:

• • The thalloid or leafy gametophyte attaches to the substratum by unicellular or multicellular rhizoids (Event B).

Sexual reproduction in moist environments:

• • Male sex organs (antheridia) produce biflagellate antherozoids that are released into film of water (Event E).
• • Antherozoids swim and reach the neck of the flask-shaped female sex organ (archegonium). An antherozoid fuses with the non-motile egg cell to form a diploid zygote (Event A).

Development of the parasitic sporophyte and spore dissemination:

• • Zygotes do not undergo reduction division immediately. They divide mitotically to produce a multicellular diploid body called the sporophyte (differentiated into foot, seta, and capsule) attached to and nourished by the gametophyte (Event D).
• • Some cells of the capsule (spore mother cells) undergo reduction division (meiosis) to produce haploid spores (Event C).
• • These spores later disperse and germinate into new gametophytes, completing the alternation of generations.

The natural biological progression is B -> E -> A -> D -> C, which corresponds to Option (3).

Gymnosperms are vascular seed plants (tracheophytes) displaying unique reproductive morphology:

• • Etymology: Greek *gymnos* = naked, and *sperma* = seed.
• • Unlike angiosperms, gymnosperms do not produce flowers and lack a carpel/ovary to enclose their megasporangia (ovules).
• • The ovules are borne naked on the surface of specialized reproductive leaves termed megasporophylls, usually aggregated into female strobili or cones (except in *Cycas* where female cones are absent).

Post-fertilization fate of naked ovules:

• • Because ovary walls are completely absent, no fruit is ever formed.
• • The ovules develop directly into mature seeds that remain uncovered and exposed to the environment (naked seeds).
• • Endosperm in gymnosperms is haploid ($n$) and forms before fertilization as the female gametophyte tissue.

The defining diagnostic hallmark of gymnosperms is that their seeds are naked, matching Option (2).

Correlating each plant genus to its corresponding botanical division in NCERT:

• • A. Pteridophyte: *Salvinia* is a small, free-floating aquatic pteridophyte (heterosporous fern producing microspores and megaspores). Hence, A matches IV.
• • B. Bryophyte: *Polytrichum* is an advanced moss belonging to Class Bryopsida (along with *Funaria* and *Sphagnum*), possessing an upright leafy gametophyte and complex sporophyte. Hence, B matches III.
• • C. Angiosperm: *Salvia* is a dicotyledonous flowering plant belonging to Family Lamiaceae, renowned for its lever-mechanism of entomophilous pollination. Hence, C matches I.
• • D. Gymnosperm: *Ginkgo* (*Ginkgo biloba*) is a gymnosperm possessing fan-shaped leaves and naked seeds, famously described as a living fossil. Hence, D matches II.

Synthesizing the code:

• • A (Pteridophyte) -> IV (*Salvinia*)
• • B (Bryophyte) -> III (*Polytrichum*)
• • C (Angiosperm) -> I (*Salvia*)
• • D (Gymnosperm) -> II (*Ginkgo*)

The code A-IV, B-III, C-I, D-II uniquely corresponds to Option (2).

In hepaticopsid bryophytes (liverworts like *Marchantia*), the gametophytic thallus produces specialized reproductive propagules called gemmae:

• • Gemma cups: Small, crescent- or cup-shaped receptacles located on the dorsal surface of the thallus along the midrib.
• • Gemmae: Green, photosynthetic, multicellular, disc-shaped vegetative bodies attached by tiny stalks inside the gemma cup.

How gemmae establish new colonies:

• • Rain drops splashing into the gemma cups break the delicate stalks, disseminating the gemmae onto moist soil.
• • Each gemma possesses two lateral growing notches containing meristematic cells.
• • Upon detachment, each notch germinates mitotically into a new haploid gametophytic thallus genetically identical to the parent.
• • Because no meiosis or fusion of gametes is involved, this represents pure asexual reproduction.

Gemmae function exclusively in asexual reproduction, matching Option (2).

Asexual reproduction in most brown algae is by biflagellate zoospores that are pear-shaped and have two unequal laterally attached flagella. Statement A is true.

Sexual reproduction may be isogamous, anisogamous or oogamous. Union of gametes may take place in water or within the oogonium (oogamous species). Restricting it to "oogamous method only" is factually incorrect. Statement B is false.

- Statement C: Food is stored as complex carbohydrates, which may be in the form of laminarin or mannitol. True. - Statement D: Brown algae possess chlorophyll a, c, carotenoids and xanthophylls (fucoxanthin). True. - Statement E: The vegetative cells have a cellulosic wall usually covered on the outside by a gelatinous coating of algin. True.

Statements A, C, D, and E are correct, corresponding to Option (1).

Heterospory is the condition of producing two morphologically distinct types of spores differing in size and sexual differentiation:

Pteridophytes are classified based on spore type as follows:

The retention of the megaspore within the megasporangium on the parent sporophyte in heterosporous pteridophytes like Selaginella and Salvinia represents the crucial evolutionary precursor to the seed habit in spermatophytes.

The dominant haploid free-living gametophyte of mosses (Bryopsida, e.g., $\textit{Funaria, Polytrichum, Sphagnum}$) consists of two sequential phases:

Following reduction division (meiosis) inside the sporophyte capsule, haploid spores are dispersed. Upon landing on suitable moist substratum, a spore germinates directly into a primary protonema:

Because the protonema is the direct, immediate vegetative germination product of the meiotic spore, it is canonically established as the primary/first stage of the gametophytic generation. Hence, Reason R correctly explains Assertion A.

In gymnosperms, pollen grains develop inside microsporangia on male strobili. Upon maturity, the microsporangia dehisce and pollen grains are shed and transported through the atmosphere exclusively via wind currents:

Pollen grains land on the micropyle of the naked ovule, NOT at the mouth of archegonia directly. Pollen grains germinate to produce a pollen tube that digests nucellar tissue, grows toward the archegonium, and discharges sperm contents. Hence, gymnosperms are siphonogamous:

NCERT states verbatim: "The pollen tube carrying the male gametes grows towards archegonia in the ovules and discharge their contents near the mouth of the archegonia."

In plant morphology, the distribution of sex organs defines sexual condition:

Chara is an advanced green macroalga (stonewort). It produces specialized multicellular, jacketed sex organs situated at the nodes of lateral branches of limited growth: - Oogonium (Nucule): The female organ situated in the upper position. - Antheridium (Globule): The male organ situated directly below the nucule. Because both fertile organs develop together on the same individual node, Chara is canonically monoecious.

Analysis of the distractors confirms strict dioecy: - *Carica papaya* (Papaya): Produces male (staminate) and female (pistillate) flowers on entirely separate trees (dioecious angiosperm). - *Marchantia polymorpha*: A dioecious hepatic (liverwort) bearing male antheridiophores and female archegoniophores on separate gametophytic thalli. - *Cycas circinalis*: A dioecious gymnosperm bearing microsporophylls clustered into male cones on male trees, and megasporophylls loosely arranged on female trees.

Gemmae (singular: gemma) are specialized vegetative propagules found in bryophytes:

In liverworts such as *Marchantia*, gemmae develop inside cup-shaped receptacles called gemma cups positioned along the midrib on the dorsal surface of the gametophytic thallus.

When rain drops splash into the gemma cups, the mature gemmae detach from their stalks, get washed away, and germinate directly to establish new haploid thalli.

The major classes of algae are classified based on photosynthetic pigments and the chemical nature of stored food reserves:

Evaluating each genus provided in the choices: - *Ectocarpus*: Filamentous brown alga belonging to Phaeophyceae $\implies$ stores mannitol and laminarin. - *Gracilaria*: Red alga belonging to Rhodophyceae $\implies$ stores floridean starch. - *Volvox*: Colonial green alga belonging to Chlorophyceae $\implies$ stores standard starch. - *Ulothrix*: Filamentous green alga belonging to Chlorophyceae $\implies$ stores standard starch.

While the majority of pteridophytes produce spores of similar kind (homosporous), select genera produce two distinct kinds of spores differing in size and developmental fate:

Plants exhibiting this dimorphic spore condition are termed heterosporous. The classic NCERT examples in pteridophytes are *Selaginella* and *Salvinia* (as well as *Marsilea* and *Azolla*).

Heterospory is considered an essential evolutionary prerequisite to the development of the seed habit because the female gametophyte is retained on the parent sporophyte.

Certain marine brown and red algae produce large amounts of hydrocolloids (water-holding phycocolloids) in their cell walls:

Carrageen (derived notably from the red seaweed *Chondrus crispus* or Irish moss) is a sulfated galactan polysaccharide widely utilized as a thickening, stabilizing, and gelling agent in food products and pharmaceutical formulations.

Chlorophyceae store true starch (amylose + amylopectin); Phaeophyceae store complex carbohydrates as laminarin or mannitol; Rhodophyceae store reserve food as Floridean starch.

Floridean starch is a branched alpha-glucan polysaccharide containing alpha-(1->4)-glucosidic linear linkages and frequent alpha-(1->6)-glucosidic branch points.

Because of its branched structure, it closely resembles amylopectin (the branched fraction of plant starch) and glycogen (animal starch). In contrast, cellulose is an unbranched beta-(1->4)-glucan.

NCERT explicitly states: "The food is stored as floridean starch which is very similar to amylopectin and glycogen in structure."

NCERT explicitly highlights: "Chlorella and Spirulina are unicellular algae rich in proteins and are used as food supplements even by space travellers."

Laminaria and Sargassum belong to Phaeophyceae (brown algae); they possess complex multicellular thalli (kelps reaching up to 100 meters) differentiated into holdfast, stipe, and frond.

Gelidium and Gracilaria are multicellular Rhodophyceae (red algae) harvested commercially for extraction of agar-agar.

Volvox is a colonial green alga (coenobium of thousands of cells connected by cytoplasmic strands), not a unicellular organism.

In pteridophytes, the main plant body is a sporophyte which bears sporangia subtended by leaf-like appendages called sporophylls. In some pteridophytes, sporophylls aggregate compactly at the apex of stems to form distinct cones or strobili.

NCERT explicitly names two classic genera bearing strobili or cones: Selaginella (club moss) and Equisetum (horsetail).

Salvinia is an aquatic heterosporous fern where sporangia are enclosed in sporocarps; Pteris is a fern whose sporangia are clustered in marginal sori under false indusia; Marchantia is a dioecious bryophyte bearing antheridiophores and archegoniophores, not strobili.

Equisetum possesses a prominent apical cone/strobilus on fertile aerial shoots.