Sexual Reproduction in Flowering Plants – Class 10 Notes

Sexual reproduction in plants involves the transfer of pollen, containing male gametes, to the stigma of the flower. This leads to fertilization within the ovary, forming seeds. Ovary may develop into fruit for seed protection and dispersal. Seeds spread through wind, water, or animals, and under favorable conditions, germinate to give rise to new plants, completing the reproductive cycle.

Sexual Reproduction in Flowering Plants

In angiosperms the reproductive part is located in the flower. The different parts of a flower are sepals, petals, stamens, and carpels. Stamen and carpel forms the reproductive part of the flower that contains the germ cells. The petals of a flower attracts pollinators, such as insects or birds, with their colorful appearances and fragrance. Sepals protect the developing flower bud and supports the petals. Flowers may be unisexual, like papaya and watermelon, containing either stamens or carpels, or bisexual, such as Hibiscus and mustard, having both stamens and carpels.

Structure of Flower

Flower consists of the different parts organised in a particular manner. They perform specific functions neccessary for the reproduction process. The parts of the flowers are as follows:

Calyx: It forms the outermost part of the flower, often green in color and is leaf like. The basic unit of calyx is known as sepal. It act as a protective covering for the developing flower bud. It can be prominent or absent in the flower.

Corolla: It consists of petals and forms the most colorful part of the flower. The basis unit of corolla is petal. It attract various pollinators like insects and birds due to their bright colors and different attractive patterns.

Reproductive Structure of a Flower

Flowers are the reproductive organs of plants, and they contain both male and female reproductive structures. Male reproductive part is known as Androecium and female reproductive part is known as Gynoceium.

Androecium

It forms the male reproductive part of the flower and consists of all the stamen present in the flower. Stamen produces pollen grain that is yellowish dust like powder. Pollen contains the male gametes (sperm cells), essential for fertilizing the female reproductive organs and enabling sexual reproduction. Stamen is divided into two parts i.e anther and filament.

Anther: It forms the top most part of the stamen and produces and releases the pollen. Pollen grains consists of the male gametes, that fertilizes the female reproductive organs of the flower.

Filament: It is a thin, stalk-like structure that carries the anther. It keeps the anther it in place for maximum exposure to the pollinators.

Microsporangia are small structures present within the anthers of a flower. It undergoes meiosis and produces microspores. The microspore develops into pollen grains, that contain the male germ cells or male gametes necessary for fertilization in flowering plants.

Gynoecium

It forms the female reproductive part Carpel. It is present at the centre of the flower and is divided into three parts as follows:

Ovary: Ovary forms the bottom swollen part of the carpel. It contains ovule and each ovule has an egg cell.

Style: Style forms the middle elongated part of the carpel. It connects the stigma and the ovary, allowing pollen tubes to reach the ovules for fertilization.

Stigma: Stigma forms the terminal part of the carpel. It is the sticky in nature and captures pollen for fertilization.

Megasporangia are specialized structures present within the ovules of a flower. They undergoes meiosis and produce megaspores, which later develops into the female gametophytes. It contains the egg cells necessary for fertilization in flowering plants.

Fertilization in plants is a process in which the male gamete (germ cell) fuses with the female gametes( egg cells) within the ovule, forming a zygote. The zygote develops into embryo within the seed, that give rise to a new plant. The process of fertilization is aided by pollination. Pollination is the transfer of pollen from a flower’s male reproductive part (anther) to its female reproductive part (stigma), enabling fertilization and seed formation. It is of two types:

• Self pollination: When the transfer of pollen occurs in the same flower.
• Cross pollination: When the pollen is transferred from one flower to another.

Process of Fertilization in Flowering Plants

The process of fertilization in the flowering plants takes place in the following way:

• Pollen is transferred from male reproductive part i.e anther to female reproductive part i.e stigma. The process is often aided by wind, insects, or animals.
• A pollen tube grows down the style starting from the pollen grain toward the ovary.
• When the pollen tube reaches the ovary, it releases the sperm cell into it.
• Only one sperm cell fuses with the egg cell, forming a zygote. This step is known as fertilization.
• Another sperm cells combines with two other cells, forming endosperm, a nutritive tissue. This process is known as double fertilization.
• The zygote develops into an embryo within the ovule. The fertilized ovule matures into a seed, containing an embryo, endosperm, and protective seed coat.
• The ovary develops into a fruit that protects the seeds and aids in dispersal. Seeds are spread by wind, water, animals, or mechanical means.
• Under favorable conditions, a seed sprouts, and the embryo develops into a new plant.

Examples of Sexual Reproduction

Examples of sexual reproduction with unisexual or bisexual types of plants are as follows:

• Corn plants(Zea Mays) produce separate male flowers (tassels) and female flowers (ears) on the same plant. Wind carries pollen from tassels to ears, facilitating fertilization and kernel formation.
• Oak Trees (Quercus spp.) produce male flowers (catkins) and female flowers on the same tree. Wind disperses pollen from catkins to female flowers, resulting in acorn formation.
• Apple Trees (Malus domestica) produce flowers with male stamens and female pistils. Pollination occurs when bees or other insects transfer pollen between flowers, leading to fertilization and the formation of apple seeds within the fruit.
• Strawberry Plants (Fragaria spp.) have white flowers with multiple carpels, and they are often pollinated by bees. The seeds embedded on the strawberry’s surface are the result of sexual reproduction.

Characteristics of Sexual Reproduction

The characteristics of sexual reproduction are as follows:

• Offspring inherit genetic material from both parents, leading to diversity within the population.
• Specialized sex cells (sperm and egg) are produced by each parent.
• Fusion of gametes during fertilization creates a zygote, which develops into a new individual.
• Genetic recombination during meiosis produces unique combinations of genes in each offspring
• Sexual reproduction accelerates evolution by generating diverse genetic traits for natural selection.
• Compared to asexual reproduction, the process is generally slower due to the involvement of two parents and the complexities of mating.

FAQs on Sexual Reproduction in Flowering Plants

1. What is sexual reproduction in plants?

Answer:

Sexual reproduction in plants involves the transfer of pollen, containing male gametes, to the stigma of the flower. This leads to fertilization within the ovary, forming seeds. Seeds germinate into new plant.

2. What are the male and female reproductive structures in a flower?

Answer:

The male reproductive structure is the stamen, which consists of the anther (producing pollen) and filament. The female reproductive structure is the pistil or carpel, comprising the stigma (pollen receptive), style, and ovary.

3. How does pollination contribute to sexual reproduction?

Answer:

Pollination is the transfer of pollen from the anther to the stigma. It facilitates the introduction of male gametes to the female reproductive parts, initiating the fertilization process.

4. What happens during fertilization in plants?

Answer:

Fertilization in plants is a process in which the male gamete (germ cell) fuses with the female gametes( egg cells) within the ovule, forming a zygote. The zygote develops into embryo within the seed, that give rise to a new plant.

5. What is double fertilization in plants?

Answer:

Only one sperm cell fuses with the egg cell, forming a zygote. This step is known as fertilization. Another sperm cells combines with two other cells, forming endosperm, a nutritive tissue. This process is known as double fertilization.