How Sexual Reproduction in Plants Ensures Diversity and Survival
Let's have a look at our daily food intake. From breakfast cereals and fruits to the chapatis and vegetables we eat in our diet comes from plants. Thus, plants are the primary source of food for human beings.
But have you ever wondered how these plants produce grains like wheat, rice or the delicious fruits and vegetables we eat?
The answer to this question is very simple, it is all a result of sexual reproduction in plants. Let us understand the mechanism of sexual reproduction in plants and it's fruitful result.
How Do Plants Reproduce Sexually?
Flower are the structural units that favour sexual reproduction in plants. A flower has the following parts-
Sepals- they are green coloured and are distinctively seen when the flower is in bud stage.
Petals- the beautiful coloured part of flowers.
Androecium - it is the male reproductive part and is composed of the anther (contains male gametes) and filament.
Gynoecium - it is the female reproductive part and comprises stigma, style and ovary (contains female gametes).
Some plants may have both male and female flowers on the same plant and are referred to as monoecious whereas some plants have male and female flowers on different plants and are referred to as dioecious.
Mechanism of Sexual Reproduction
Sexual reproduction involves the fusion of male and female gametes. For this event to occur firstly the male and female gametes must be brought to the vicinity, which is achieved by pollination.
Pollination: Pollination is the transfer of pollen grains (containing male gametes) from another to the stigma of flowers. This process is aided by various biotic (living organisms such as bees, wasps, ants, animals, and human beings) and abiotic factors (non-living factors such as wind, water).
Plants have evolved various mechanisms to favour pollination.
Anemophily - pollination by wind. The tassels of maize are evolved to capture pollen in wind. This type of pollination is common in cereal crops, grasses etc.
Hydrophily - pollination by water. Pollen grains are carried away by water currents and cause pollination in aquatic as well as many terrestrial plants.
Zoophily - pollination by animals and insects. The pollen gets adhered to the body of insects and animals and is transported from one place to another.
After pollination, the pollen grains on reaching the stigma of flowers germinate and give rise to pollen tubes that penetrate stigma and grow inside style to reach the ovary. This leads to the next step fertilization.
Fertilization - It involves the fusion of male and female gametes. The pollen tube on reaching the ovary releases 2 male gametes which then enter the ovary through micropyle opening and fuse with female gametes in the embryo sac. This results in the formation of zygote.
How Does Sexual Reproduction Benefit Humans?
The zygote formed as a result of fertilization develops into a seed and the ovary develops into fruit both of which are important products for human beings. Wheat, Rice, Maize etc. are all seeds developed from the zygote and the fruits and vegetables we eat are ripened ovaries. Thus we are fortunate that plants reproduce sexually.
FAQs on Why Are We Fortunate That Plants Reproduce Sexually?
1. Why are we fortunate that plants reproduce sexually?
We are fortunate because sexual reproduction in plants is the primary source of genetic variation. This variation is directly responsible for the vast diversity of flowers, fruits, and vegetables we enjoy. It allows breeders to create new crop varieties that are more nutritious, disease-resistant, and have higher yields, ensuring our food security. The beautiful ornamental plants that enrich our environment are also a product of this process.
2. What is the main difference between pollination and fertilisation in flowering plants?
Pollination and fertilisation are two distinct but sequential events. Pollination is the physical transfer of pollen grains from the anther to the stigma of a flower. In contrast, fertilisation is the biological process that occurs after successful pollination, involving the fusion of the male gamete (from the pollen) with the female gamete (the egg cell) inside the ovule to form a zygote.
3. What is double fertilisation and why is it a unique and efficient process in angiosperms?
Double fertilisation is a complex process exclusive to flowering plants (angiosperms) involving two separate fusions within the embryo sac:
Syngamy: One male gamete fuses with the egg cell to form the zygote (2n), which develops into the embryo.
Triple Fusion: The second male gamete fuses with the two polar nuclei in the central cell to form the Primary Endosperm Nucleus (PEN) (3n).
This process is highly efficient because the nutritive tissue (endosperm) only develops after fertilisation is confirmed, preventing the plant from wasting resources on an unfertilised ovule.
4. How does a flower’s pistil recognise and accept only the correct type of pollen?
This recognition is managed through a sophisticated mechanism called pollen-pistil interaction. The surface of the stigma contains specific proteins and chemicals that act like a lock-and-key system. If the pollen grain is from a compatible plant, it is 'recognised' and accepted, allowing it to germinate and grow a pollen tube. If the pollen is from another species or is incompatible, the pistil rejects it by preventing germination, ensuring successful reproduction with a suitable partner.
5. What are the key components of a mature embryo sac in a flowering plant as per the CBSE 2025-26 syllabus?
A typical mature embryo sac is a 7-celled, 8-nucleate structure. Its components are:
Egg Apparatus: Located at the micropylar end, it has one egg cell and two synergids.
Central Cell: The largest cell, containing two polar nuclei.
Antipodal Cells: Three cells at the chalazal end, which typically degenerate after fertilisation.
6. What is the functional importance of an endosperm compared to an embryo in a seed?
The embryo and endosperm have distinct and crucial roles. The embryo is the miniature, dormant plantlet itself, containing the radicle (future root), plumule (future shoot), and cotyledons (seed leaves). The endosperm, on the other hand, is not part of the embryo but serves as its dedicated food supply, providing nourishment during germination until the new seedling can produce its own food through photosynthesis.
7. What would happen if triple fusion occurred in a flower but syngamy failed?
This is a hypothetical scenario that highlights the dependency of the processes. If triple fusion occurred, the Primary Endosperm Nucleus (PEN) would form and develop into the endosperm. However, since syngamy (the fusion of a male gamete with the egg) failed, no zygote and therefore no embryo would be formed. The result would be a seed-like structure containing nutritive tissue but lacking an embryo, rendering it non-viable and unable to germinate into a new plant.
8. If asexual reproduction is faster, why is sexual reproduction considered a superior long-term strategy for plant survival?
While asexual reproduction is faster and energetically cheaper, it produces genetically identical offspring (clones). This lack of diversity makes the entire population vulnerable to a single disease, pest, or environmental change. Sexual reproduction, by creating genetic recombination, produces varied offspring. This variation acts as an evolutionary insurance policy, increasing the probability that some individuals will have traits that allow them to survive and adapt to new challenges, ensuring the long-term survival of the species.
9. What are some examples of plants that have adapted to different agents of pollination?
Plants show remarkable adaptations for their specific pollinating agents:
Wind Pollination (Anemophily): Plants like maize and grasses have small, inconspicuous flowers and produce large amounts of light, non-sticky pollen.
Insect Pollination (Entomophily): Plants like roses and sunflowers have large, colourful, fragrant flowers and produce nectar to attract insects.
Water Pollination (Hydrophily): Aquatic plants like Vallisneria have specialised mechanisms where female flowers reach the water surface to receive pollen grains carried by water currents.
