What is Sexual Reproduction in Plants?
Sexual reproduction in plants involves two parent organisms contributing genetic information to produce offspring. Each parent provides specialised sex cells or gametes (male and female). These gametes fuse during fertilisation, leading to the formation of a zygote, which eventually develops into a new plant. This process allows for greater genetic variation in the offspring compared to asexual reproduction.
Characteristics of Sexual Reproduction
Involvement of Two Parents: Both male and female organisms (or reproductive parts) produce gametes.
Gamete Formation and Fusion: Male and female gametes fuse to form a zygote.
Genetic Variation: Since genetic material from two parents mixes, offspring often show differences in physical and genetic traits.
Slower Process: Sexual reproduction generally takes more time as it involves pollination, fertilisation, and seed formation.
Adaptability: Variations can help plant species adapt to changing environments.
These characteristics of sexual reproduction highlight why it is an important mode of reproduction in many organisms, including plants.
Male and Female Reproductive Parts in a Flower
Most flowering plants have a specialised structure called the flower, which is the main site of sexual reproduction. A complete flower typically has four parts: sepals, petals, stamen, and pistil (also known as carpel).
Stamen (Male Part)
Anther: Produces and stores pollen grains, which contain the male gametes.
Filament: A stalk-like structure supporting the anther.
Pistil (Female Part)
Stigma: Receives pollen grains, usually sticky to help pollen adhere.
Style: A tubular structure connecting the stigma to the ovary.
Ovary: Contains ovules, each housing the female gamete (egg cell). After fertilisation, the ovary develops into the fruit.
A Flower Can Be:
Unisexual: Has either stamen or pistil (e.g. papaya, cucumber).
Bisexual: Has both stamen and pistil (e.g. rose, china rose).
Pollination
For fertilisation to occur, pollen grains from the anther must reach the stigma. This transfer of pollen is called pollination. It can be of two types:
Self-Pollination: Pollen transfers from the anther to the stigma of the same flower or another flower on the same plant.
Cross-Pollination: Pollen transfers from the anther of one plant to the stigma of a different plant of the same species.
Pollination often relies on pollinators such as insects (bees, butterflies), birds, wind, and water.
Fertilisation
Once pollen grains land on the stigma, they germinate to form a pollen tube that grows down through the style, reaching the ovary. The male gametes travel through this tube and fuse with the egg (female gamete) inside the ovule. This fusion is known as fertilisation, resulting in the formation of a zygote. The zygote divides repeatedly to become an embryo, which eventually matures into a seed.
Formation of Seeds and Fruits
After Fertilisation:
Each ovule develops into a seed, containing the embryo and stored food for its initial growth.
The ovary transforms into a fruit, protecting the seeds until they are dispersed.
When conditions are favourable, seeds germinate to produce new plants, thereby completing the life cycle.
Sexual Reproduction in Plants Diagram
Below is a simplified outline of how sexual reproduction occurs in a typical flower:
Stamen releases pollen.
Pollen lands on the stigma (pollination).
Pollen tube grows towards the ovary.
Male gamete fuses with the egg cell (fertilisation).
Zygote develops into an embryo.
Ovule becomes a seed, ovary becomes a fruit.
This sexual reproduction in plants diagram helps visualise the key stages involved.
10 Examples of Plants That Reproduce Sexually
Many flowering plants rely on sexual reproduction. Here are 10 examples of plants that reproduce sexually:
Rose
China rose (Hibiscus)
Sunflower
Papaya
Tomato
Pea plant
Cucumber
Apple tree
Mango tree
Coconut palm
These examples of sexual reproduction in plants show a diverse range of species with distinct modes of pollination and fertilisation.
Quick Quiz (With Answers)
1. Which part of the flower produces pollen?
Answer: Anther (part of the stamen).
2. Name the female reproductive part of a flower.
Answer: Pistil (carpel), which consists of stigma, style, and ovary.
3. What is fertilisation in plants?
Answer: The fusion of male and female gametes inside the ovule.
4. Give one difference between self-pollination and cross-pollination.
Answer: Self-pollination occurs within the same flower or plant, while cross-pollination involves different plants of the same species.
5. What does the ovary develop into after fertilisation?
Answer: The ovary develops into a fruit.
Related Topics
FAQs on Sexual Reproduction in Plants
1. What is sexual reproduction in flowering plants as per the CBSE Class 12 syllabus for the 2025-26 session?
Sexual reproduction in flowering plants (angiosperms) is a biological process involving the fusion of male and female gametes to form a zygote. This process begins with pollination, followed by fertilization, and concludes with the formation of a seed and fruit. It introduces genetic variation, which is crucial for the adaptation and evolution of plant species.
2. What are the main reproductive parts of a typical flower and their functions?
The reproductive parts of a flower are organised into male and female whorls.
- The male reproductive part is the stamen, which consists of the anther (produces pollen grains containing male gametes) and the filament (a stalk that supports the anther).
- The female reproductive part is the pistil or carpel, which includes the stigma (a receptive tip that receives pollen), the style (a tube connecting the stigma to the ovary), and the ovary (contains the ovules, which house the female gamete or egg cell).
3. What are the key steps in the process of sexual reproduction in plants?
The sexual reproduction process in flowering plants follows five main steps:
- Pollination: The transfer of pollen grains from the anther to the stigma.
- Pollen Germination: The pollen grain forms a pollen tube that grows down the style towards the ovule.
- Fertilisation: The fusion of male gametes with the female gamete (egg cell) and the central cell inside the ovule. This is known as double fertilisation in angiosperms.
- Seed Formation: After fertilisation, the ovule develops into a seed, containing the embryo and a food store.
- Fruit Formation: The ovary matures and develops into a fruit, which protects the seeds and aids in their dispersal.
4. What is the difference between self-pollination and cross-pollination?
The primary difference lies in the source of the pollen. In self-pollination, pollen is transferred from the anther to the stigma of the same flower or another flower on the same plant. In cross-pollination, pollen is transferred from the anther of a flower on one plant to the stigma of a flower on a different plant of the same species. Cross-pollination promotes greater genetic diversity.
5. Why have many flowering plants evolved to have large, colourful petals and produce nectar?
These features are adaptations to attract biotic pollinators such as insects, birds, and bats. Large, brightly coloured petals act as visual signals, while nectar serves as a food reward. By attracting these animals, plants ensure the efficient transfer of pollen for cross-pollination, which is often necessary for successful reproduction and maintaining genetic health in the population.
6. What is double fertilisation and why is it a unique feature of flowering plants?
Double fertilisation is a complex process unique to angiosperms (flowering plants). It involves two separate fusion events within the ovule:
- Syngamy: One male gamete fuses with the egg cell to form the diploid zygote, which develops into the embryo.
- Triple Fusion: The second male gamete fuses with the two polar nuclei in the central cell to form the triploid primary endosperm nucleus (PEN), which develops into the nutritive endosperm.
7. How do outbreeding devices in plants help promote genetic variation?
Outbreeding devices are mechanisms that discourage self-pollination and encourage cross-pollination. By promoting the fusion of gametes from different plants, they increase genetic variation. Examples include:
- Self-incompatibility: A genetic mechanism that prevents self-pollen from fertilising the ovules.
- Dichogamy: The anthers and stigma mature at different times, preventing self-pollination within the same flower.
- Heterostyly: The presence of different lengths of stamens and styles in flowers of the same species to prevent self-pollination.
8. What happens to the ovule and ovary after successful fertilisation?
After fertilisation, significant changes occur within the flower. The fertilised ovule develops into a seed, which contains the embryo and a food source. Simultaneously, the wall of the ovary develops into the pericarp (the wall of the fruit). The entire mature ovary, containing one or more seeds, becomes the fruit.
9. What is the key difference between parthenocarpy and apomixis in plants?
Both are special modes of reproduction, but they differ in their outcomes. Parthenocarpy is the development of fruit without fertilisation, which typically results in seedless fruits like bananas. In contrast, apomixis is the formation of a viable seed without fertilisation. It is a form of asexual reproduction that mimics sexual reproduction, producing offspring that are genetically identical to the parent plant.
10. Why is the endosperm crucial for the early life of a plant?
The endosperm is a nutritive tissue that provides essential food and nourishment to the developing embryo inside the seed. It acts as a packed lunch, supplying energy and nutrients during the critical stages of seed germination and early seedling growth, before the young plant is capable of producing its own food through photosynthesis.
