NCERT Solutions for Class 11 Biology Chapter 3 Plant Kingdom
NCERT Solutions for Class 11 Biology Chapter 3 Plant Kingdom covers the classification of plants into major groups: Algae, Bryophytes, Pteridophytes, Gymnosperms, and Angiosperms, alongside life cycle patterns and alternation of generations.
Overview of Topics & Subtopics (Click to Jump)
1. Algae
Short Note:
• Chlorophyll-bearing, simple, thalloid, autotrophic, and largely aquatic (freshwater and marine) organisms.
• Chlorophyceae (Green Algae): Dominant pigments: Chlorophyll a and b. Stored food: Starch (in pyrenoids). Cell wall: Cellulose and pectose. Examples: Volvox, Ulothrix, Spirogyra, Chlamydomonas.
• Phaeophyceae (Brown Algae): Dominant pigments: Chlorophyll a, c, and Fucoxanthin. Stored food: Laminarin or mannitol. Plant body attached to substrate by holdfast, has a stalk (stipe) and leaf-like frond. Examples: Ectocarpus, Laminaria, Sargassum, Fucus.
• Rhodophyceae (Red Algae): Dominant pigments: Chlorophyll a, d, and r-phycoerythrin. Stored food: Floridean starch. Mostly marine, multi-cellular. Non-motile spores and gametes. Examples: Polysiphonia, Porphyra, Gracilaria, Gelidium (agar source).
2. Bryophytes
Short Note:
• Known as Amphibians of the Plant Kingdom because they live in soil but depend on water for sexual reproduction (flagellated antherozoids swim in water to reach archegonium).
• Lack true roots, stem, or leaves; attached to substrate by unicellular or multicellular rhizoids.
• Dominant phase is gametophyte (haploid, produces gametes). Sporophyte is dependent on gametophyte for nourishment.
• Liverworts: Thalloid body (e.g., Marchantia). Reproduce asexually by fragmentation or specialized structures called gemmae (green, multicellular asexual buds produced in gemma cups).
• Mosses: Dominant stage consists of two stages: Protonema stage (creeping, green, branched) and Leafy stage (bears sex organs). Examples: Funaria, Polytrichum, Sphagnum (peat moss used as fuel and packing material).
3. Pteridophytes
Short Note:
• First terrestrial plants to possess vascular tissues (Xylem and Phloem). Found in cool, damp, shady places.
• Dominant plant body is a sporophyte (diploid) differentiated into true root, stem, and leaves.
• Sporophytes bear sporangia subtended by leaf-like appendages called sporophylls (may form compact cones/strobili e.g., Selaginella, Equisetum).
• Spores germinate to form an inconspicuous, small, free-living, photosynthetic thalloid gametophyte called prothallus.
• Heterospory & Seed Habit: Genera like Selaginella and Salvinia produce two kinds of spores—macro (mega) and micro spores. Development of zygote into embryo inside female gametophyte retained on parent sporophyte is an important precursor to the seed habit.
4. Gymnosperms & Angiosperms
Short Note:
• Gymnosperms: Seed plants in which ovules are not enclosed by an ovary wall; seeds remain exposed (naked seeds). Includes tall trees (e.g., Sequoia - giant redwood) and medium-sized shrubs. Roots often have fungal association (Mycorrhiza in Pinus) or specialized coralloid roots fixing nitrogen (in Cycas). Heterosporous (microspores and megaspores).
• Angiosperms: Flowering plants where seeds are enclosed inside fruits. Divided into Dicots (two cotyledons, reticulate venation, tetramerous/pentamerous flowers) and Monocots (single cotyledon, parallel venation, trimerous flowers). Exhibit unique process of Double Fertilisation (Syngamy + Triple Fusion producing 3n Endosperm).
5. Plant Life Cycles & Alternation of Generations
Short Note:
• Both haploid and diploid cells in plants can divide by mitosis, leading to alternation between gamete-producing haploid gametophyte ($n$) and spore-producing diploid sporophyte ($2n$).
• Haplontic: Dominant phase is haploid gametophyte; diploid stage represented only by single-celled zygote (meiosis occurs in zygote). E.g., Volvox, Spirogyra, Chlamydomonas.
• Diplontic: Dominant photosynthetic phase is diploid sporophyte; gametophytic phase represented by single- to few-celled stage. E.g., All seed-bearing plants (Gymnosperms & Angiosperms), Fucus (brown alga).
• Haplo-diplontic: Both phases are multicellular and prominent. E.g., Bryophytes, Pteridophytes, and algae like Ectocarpus, Polysiphonia, Kelps.
Intext & Conceptual Questions
Heterospory is the phenomenon of producing two morphologically distinct types of spores by the same plant—smaller microspores and larger megaspores.
Significance:
1. Microspores germinate to give rise to male gametophytes, while megaspores give rise to female gametophytes.
2. The female gametophyte is retained on the parent sporophyte for variable periods, providing nourishment to the developing embryo.
3. This retention and localized embryo development is considered a crucial evolutionary precursor to the seed habit seen in higher plants.
Examples: Selaginella and Salvinia.
Textbook Chapter End Exercise Questions
| Feature | Liverworts | Mosses |
|---|---|---|
| Plant Body | Dorsiventrally flattened, thalloid structure (e.g., Marchantia). | Erect structure with stem-like, leaf-like, and root-like rhizoids. |
| Protonema Stage | Absent. | Present (juvenile filamentous stage germinating from spore). |
| Asexual Reproduction | Takes place via fragmentation or specialized gemmae inside gemma cups. | Takes place by fragmentation and budding in the secondary protonema. |
Bryophytes are referred to as the amphibians of the plant kingdom because although they inhabit damp, shaded terrestrial land areas, they cannot complete their life cycle without water.
Water is indispensable for their sexual reproduction: the flagellated male gametes (antherozoids) released by the antheridium require a thin film of liquid water to swim towards the archegonium and fertilize the egg cell to form a zygote.
Read More & Chapter Resources
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