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Q7:
What is vegetative propagation? Give two suitable examples.
Solution :
Step 1: Core Definition & Theoretical Framework
Vegetative propagation (also known as vegetative reproduction) is a specialized form of asexual reproduction occurring in plants. In this biological process, a new, distinct plant individual is generated from a vegetative fragment or a specialized anatomical structure of the parent plant, rather than through the fusion of gametes (sexual reproduction) or the formation of seeds.
Because the process relies exclusively on mitotic cell division ($2n \xrightarrow{\text{Mitosis}} 2n$), the offspring produced are morphologically and genetically identical to the parent plant. [Per the principles of classical genetics, such identical offspring are defined as clones]. The structures that facilitate this mode of reproduction—such as modified stems, roots, or leaves—are collectively termed vegetative propagules.
Step 2: Biological Mechanism & Justification
Vegetative propagation operates on the principle of totipotency—the ability of a single plant cell or a group of meristematic cells to divide and differentiate into an entirely new, complete organism. [By the laws of plant histology, localized regions of active cell division known as meristems remain capable of forming adventitious roots and shoots under favorable moisture and temperature conditions].
Step 3: Suitable Examples of Vegetative Propagation
Example 1: Stem Tuber in Potato (Solanum tuberosum)
- Morphological Setup: The potato is a specialized, swollen underground stem modified for starch storage.
- Propagule Mechanism: The surface of the potato tuber contains small depressions commonly referred to as "eyes." Morphologically, these eyes are nodes that house axillary buds.
- Reproductive Outcome: When a piece of the tuber containing at least one eye is planted in moist soil, the axillary bud breaks dormancy and germinates. It draws upon the stored carbohydrates in the tuber to develop adventitious roots and an aerial shoot, eventually maturing into an independent plant. [Justified by the botanical axiom that stems, unlike roots, possess distinct nodes and internodes capable of bearing buds].
Example 2: Leaf Buds in Bryophyllum
- Morphological Setup: Bryophyllum (often called the air plant) possesses broad, succulent leaves with distinctly scalloped or notched margins.
- Propagule Mechanism: Situated within the notches along the leaf margins are specialized clusters of meristematic tissue that develop into epiphyllous adventitious buds.
- Reproductive Outcome: While still attached to the parent plant, or when the leaf falls onto damp soil, these buds undergo rapid mitotic division to form miniature plantlets, complete with their own root systems and tiny leaves. Once they detach and establish soil contact, they grow into independent adult plants.
Step 4: Anatomical Visualization
The following diagram illustrates the morphological structures (vegetative propagules) responsible for asexual reproduction in the two given examples.
Step 5: Tabular Summary of Vegetative Propagules
| Plant Species | Type of Plant Part Used | Specific Vegetative Propagule | Location of Meristematic Tissue |
|---|---|---|---|
| Solanum tuberosum (Potato) | Underground Stem Modification | Stem Tuber | Axillary buds located in the "eyes" (nodes). |
| Bryophyllum | Leaf Modification | Leaf Buds | Adventitious buds at the notches of the leaf margins. |
Final Solution: Vegetative propagation is an asexual mode of plant reproduction where new, genetically identical offspring develop from somatic tissues (vegetative propagules) rather than seeds. Two prominent examples include the sprouting of stem tubers via axillary buds in the Potato (Solanum tuberosum), and the development of epiphyllous plantlets from the leaf margin notches in Bryophyllum.
More Questions from Class 12 Biology Reproduction in Organisms EXERCISES
- Q1: Why is reproduction essential for organisms?
- Q1: Why is reproduction essential for organisms?
- Q2: Which is a better mode of reproduction: sexual or asexual? Why?
- Q2: Which is a better mode of reproduction: sexual or asexual? Why?
- Q3: Why is the offspring formed by asexual reproduction referred to as clone?
- Q3: Why is the offspring formed by asexual reproduction referred to as clone?
- Q4: Offspring formed due to sexual reproduction have better chances of survival. Why? Is this statement always true?
- Q4: Offspring formed due to sexual reproduction have better chances of survival. Why? Is this statement always true?
- Q5: How does the progeny formed from asexual reproduction differ from those formed by sexual reproduction?
- Q5: How does the progeny formed from asexual reproduction differ from those formed by sexual reproduction?
- Q6: Distinguish between asexual and sexual reproduction. Why is vegetative reproduction also considered as a type of asexual reproduction?
- Q6: Distinguish between asexual and sexual reproduction. Why is vegetative reproduction also considered as a type of asexual reproduction?
- Q7: What is vegetative propagation? Give two suitable examples.
- Q8(a): Define (a) Juvenile phase,
- Q8(a): Define (a) Juvenile phase,
- Q8(b): Define (b) Reproductive phase,
- Q8(b): Define (b) Reproductive phase,
- Q8(c): Define (c) Senescent phase.
- Q8(c): Define (c) Senescent phase.
- Q9: Higher organisms have resorted to sexual reproduction in spite of its complexity. Why?
- Q9: Higher organisms have resorted to sexual reproduction in spite of its complexity. Why?
- Q10: Explain why meiosis and gametogenesis are always interlinked?
- Q10: Explain why meiosis and gametogenesis are always interlinked?
- Q11(a): Identify each part in a flowering plant and write whether it is haploid (\(n\)) or diploid (\(2n\)). (a) Ovary ———————————
- Q11(a): Identify each part in a flowering plant and write whether it is haploid ((n)) or diploid ((2n)). (a) Ovary ———————————
- Q11(b): Identify each part in a flowering plant and write whether it is haploid (\(n\)) or diploid (\(2n\)). (b) Anther ———————————
- Q11(b): Identify each part in a flowering plant and write whether it is haploid ((n)) or diploid ((2n)). (b) Anther ———————————
- Q11(c): Identify each part in a flowering plant and write whether it is haploid (\(n\)) or diploid (\(2n\)). (c) Egg ———————————
- Q11(c): Identify each part in a flowering plant and write whether it is haploid ((n)) or diploid ((2n)). (c) Egg ———————————
- Q11(d): Identify each part in a flowering plant and write whether it is haploid (\(n\)) or diploid (\(2n\)). (d) Pollen ———————————
- Q11(d): Identify each part in a flowering plant and write whether it is haploid ((n)) or diploid ((2n)). (d) Pollen ———————————
- Q11(e): Identify each part in a flowering plant and write whether it is haploid (\(n\)) or diploid (\(2n\)). (e) Male gamete ———————————
- Q11(e): Identify each part in a flowering plant and write whether it is haploid ((n)) or diploid ((2n)). (e) Male gamete ———————————
- Q11(f): Identify each part in a flowering plant and write whether it is haploid (\(n\)) or diploid (\(2n\)). (f) Zygote ———————————
- Q11(f): Identify each part in a flowering plant and write whether it is haploid ((n)) or diploid ((2n)). (f ) Zygote ———————————
- Q12: Define external fertilisation. Mention its disadvantages.
- Q12: Define external fertilisation. Mention its disadvantages.
- Q13: Differentiate between a zoospore and a zygote.
- Q13: Differentiate between a zoospore and a zygote.
- Q14: Differentiate between gametogenesis from embryogenesis.
- Q14: Differentiate between gametogenesis from embryogenesis.
- Q15: Describe the post-fertilisation changes in a flower.
- Q15: Describe the post-fertilisation changes in a flower.
- Q16: What is a bisexual flower? Collect five bisexual flowers from your neighbourhood and with the help of your teacher find out their common and scientific names.
- Q16: What is a bisexual flower? Collect five bisexual flowers from your neighbourhood and with the help of your teacher find out their common and scientific names.
- Q17: Examine a few flowers of any cucurbit plant and try to identify the staminate and pistillate flowers. Do you know any other plant that bears unisexual flowers?
- Q17: Examine a few flowers of any cucurbit plant and try to identify the staminate and pistillate flowers. Do you know any other plant that bears unisexual flowers?
- Q18: Why are offspring of oviparous animals at a greater risk as compared to offspring of viviparous animals?
- Q18: Why are offspring of oviparous animals at a greater risk as compared to offspring of viviparous animals?
CBSE Solutions for Class 12 Biology Reproduction in Organisms
Chapters in CBSE - Class 12 Biology
- Human Reproduction
- Reproductive Health
- Principles of Inheritance and Variation
- Molecular Basis of Inheritance
- Evolution
- Human Health and Disease
- Strategies for Enhancement in Food Production
- Microbes in Human Welfare
- Biotechnology: Principles and Processes
- Biotechnology and Its Applications
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
- Environmental Issues
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