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. Why is variation important in sexual reproduction?
Variation provides plants with a better chance of adapting to changing environmental conditions. This can lead to improved survival and evolution of species.
2. How does pollen reach the stigma?
Pollen can be transferred by wind, water, insects, or other animals. These are known as pollinating agents.
3. Why do some flowers produce large, colourful petals?
Bright petals often attract pollinators such as bees and butterflies, making pollination more efficient.
4. Can unisexual flowers self-pollinate?
Generally, no. Unisexual flowers have only male or female parts, so they rely on cross-pollination to ensure fertilisation.
