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Q8(i):
Explain briefly the following terms with suitable examples:- (i) protonema
Solution :
1. Theoretical Definition of Protonema
The protonema is a filamentous, haploid ($n$) structure that represents the juvenile, primary stage in the life cycle of mosses (Bryophyta). It develops directly from the germination of a haploid spore ($n$). Upon reaching a specific stage of development, the protonema differentiates into the leafy, gametophytic stage [Per the haplodiplontic life cycle model in Bryophytes].
2. Developmental Morphology
- Origin: Arises via mitosis following the germination of a spore released from the sporophyte capsule.
- Structure: Typically creeping, green, branched, and frequently filamentous.
- Physiological Role: Acts as the primary photosynthetic unit for the establishment of the young gametophyte.
- Transition: Under favorable conditions, it produces lateral buds that develop into leafy gametophores (the upright, mature stage of the moss).
3. Visual Representation of the Life Cycle Phase
4. Comparative Summary
| Feature | Description |
|---|---|
| Ploidy Level | Haploid ($n$) [By Meiosis occurring within the Sporophyte capsule] |
| Growth Pattern | Creeping and filamentous |
| Example | *Funaria* (Common cord moss), *Polytrichum* |
5. Conclusion
The protonema stage is a hallmark of moss biology, demonstrating the transition from a single-celled reproductive unit (spore) to the multicellular gametophyte ($n$). This stage is absent in liverworts, making it a critical diagnostic feature for taxonomic classification within the Bryophyta.
Final Solution: The protonema is the creeping, filamentous, juvenile haploid stage of the moss life cycle, originating from spore germination and later giving rise to the leafy gametophore, as observed in species like Funaria.
More Questions from Class 11 Biology Plant Kingdom EXERCISES
- Q1: What is the basis of classification of algae?
- Q2: When and where does reduction division take place in the life cycle of a liverwort, a moss, a fern, a gymnosperm and an angiosperm?
- Q3: Name three groups of plants that bear archegonia. Briefly describe the life cycle of any one of them.
- Q4: Mention the ploidy of the following: protonemal cell of a moss; primary endosperm nucleus in dicot, leaf cell of a moss; prothallus cell of a ferm; gemma cell in Marchantia; meristem cell of monocot, ovum of a liverwort, and zygote of a fern.
- Q5: Write a note on economic importance of algae and gymnosperms.
- Q6: Both gymnosperms and angiosperms bear seeds, then why are they classified separately?
- Q7: What is heterospory? Briefly comment on its significance. Give two examples.
- Q8(ii): Explain briefly the following terms with suitable examples:- (ii) antheridium
- Q8(iii): Explain briefly the following terms with suitable examples:- (iii) archegonium
- Q8(iv): Explain briefly the following terms with suitable examples:- (iv) diplontic
- Q8(v): Explain briefly the following terms with suitable examples:- (v) sporophyll
- Q8(vi): Explain briefly the following terms with suitable examples:- (vi) isogamy
- Q9(i): Differentiate between the following:- (i) red algae and brown algae
- Q9(ii): Differentiate between the following:- (ii) liverworts and moss
- Q9(iii): Differentiate between the following:- (iii) homosporous and heterosporous pteridophyte
- Q10: Match the following (column I with column II) Column I Column II (a) Chlamydomonas (i) Moss (b) Cycas (ii) Pteridophyte (c) Selaginella (iii) Algae (d) Sphagnum (iv) Gymnosperm
- Q11: Describe the important characteristics of gymnosperms.
CBSE Solutions for Class 11 Biology Plant Kingdom
Chapters in CBSE - Class 11 Biology
- The Living World
- Biological Classification
- Animal Kingdom
- Morphology of Flowering Plants
- Anatomy of Flowering Plants
- Structural Organisation in Animals
- Cell – The Unit of Life
- Biomolecules
- Cell Cycle and Division
- Transport in Plants
- Mineral Nutrition
- Photosynthesis
- Respiration in Plants
- Plant Growth and Development
- Digestion and Absorption
- Breathing and Exchange of Gases
- Body Fluids and Circulation
- Excretory Products and Elimination
- Locomotion and Movement
- Neural Control and Coordination
- Chemical Coordination and Integration
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