In this blog, we are going to learn about sexual reproduction in plants. Flowers are the reproductive parts of a plant. Flowers have sepals, petals, stamen, and pistils. The reproductive parts of a flower containing the germ cells are:

Unisexual and Bisexual Flowers

The flowers which have either the male reproductive part i.e. androecium or the female reproductive part i.e. gynoecium are called unisexual flowers. Corn, papaya, and cucumbers produce unisexual flowers.

The flowers which have both the male and female reproductive parts are called bisexual flowers. Mustard, rose and petunia produce bisexual flowers. Both the male and the female unisexual flowers may be present in the same plant or different plants.

A flower in which all four whorls are present is said to be a complete flower. The Four whorls are calyx, corolla, stamens, and pistils.

Parts of a flower

Calyx and corolla are referred to as the non-essential whorls since they are not required for the formation of seed.

Male reproductive part stamen

The androecium is the male reproductive part of the flower. The individual units of androecium are called stamens. Stamen is the male reproductive part that produces pollen grains that carry the male gamete and are yellowish in color.

The stamen consists of a thread-like filament and a knob-like anther at its end. The anther in stamen bears four chambers or pollen sacs each filled with a granular mass of small spores called pollen grains, which produce male gamete or reproductive cells.

Female reproductive part carpel

The gynoecium is the female reproductive part of the flower. The individual units are called the carpels or pistils. The carpel is the female reproductive part and is present in the center of the flower. It is made up of three parts.

The swollen bottom part is the ovary, a middle elongated style, and the terminal part is the stigma which may be sticky. The ovary contains ovules and each ovule has an egg cell.

The male germ-cell produced by pollen grain fuses with the female gamete present in the ovule. The fusion of the germ cells also termed syngamy or fertilization gives the zygote which is capable of growing into a new plant.

This process of transfer of pollen grains from another to stigma is called pollination. After the pollen lands on a suitable stigma, a pollen tube grows out of the pollen grain and grows downwards through the style to reach the ovary.

During its growth, two non-motile male gametes are formed inside the pollen tube. After reaching the ovary, the pollen tube enters the ovule through the micropyle and the tip of the tube finally pierces the egg apparatus in the embryo sac. After this, the tip of the pollen tube ruptures releasing two male gametes into the embryo sac. The mature embryo sac consists of an egg apparatus, two polar nuclei, and three antipodal cells.

Syngamy: The fusion of a male gamete with the egg to form a diploid zygote is called syngamy.

Now Triple fusion: The male gamete fuses with the two polar nuclei to form a triploid and the process is called triple fusion.

Double Fertilization: This mechanism involving two acts of fertilization in an embryo sac is called double fertilization. After fertilization, the zygote develops into an embryo. Ovule develops into a seed and the ovary develops into the fruit.

● Post-Fertilization

The female sex cells or gamete or egg are formed in the ovule. Male and female gamete fuse to form a zygote. After fertilization, many changes take place in the ovules. The egg cell or ovum secrets a cellulose wall around itself. The ovary begins to grow and gradually it matures into a fruit. The fruit therefore may be regarded as a mature ovary.

Fruit is composed of two parts- the pericarp and the seed. Pericarp develops from the wall of the ovary and the seed develops from the ovule. Sometimes other floral parts like the thalamus or even the calyx may grow to form a part of the fruit.

It is important to note that. Some fruits are fleshy and juicy such as mangoes, apples, peach, plum, and orange. Whereas Some fruits are hard like almonds and walnuts.

● Pollination

Transfer of pollen grains from the anther of a flower to the stigma of the same flower or of another flower of the same or sometimes allied species is called pollination. If the pollen grains are transferred to the stigma of the same flower, the pollination is called self-pollination or autogamy.

If the pollen grains of a flower are transferred to the stigma of another flower of the same species, the pollination is called cross-pollination or allogamy.

Cross-pollination is brought about by various agencies like insects, birds, animals including man, water, and wind. Generally, pollen grains have a tough protective coat that prevents them from drying up.

● Dispersion

Let us understand a very interesting phenomenon. The phenomenon of dispersion of seeds. The process by which the seeds are scattered away from the mother plant is called dispersion. Children, it is due to this phenomenon that similar types of plants can be found at different places. Children, nature has its own ways of dispersal of seeds.

Some methods of dispersal of seeds are:-

Dispersal by winds: Seeds of certain plants are very light and have wings or hair on them. These seeds are easily carried away by the wind. While strolling around a garden, you often would have seen small parts of plants stuck to your shoes, Yes, these are nothing but the seeds which have been carried away from their mother plant by the action of wind.

Children, dandelion seeds have hair that acts as a parachute. Winds carry these seeds far from the parent plant. The fluff around the cotton seed helps it to float away easily.

Dispersion by water: Another way of dispersion of seeds is dispersion by water. Seeds of some plants such as coconut and lotus are spongy and have a fibrous covering. This property helps them to keep afloat on water. Water transports these seeds from one place to another.

Dispersion by animals: Animals including human beings eat fruits and throw away seeds, around.

These thrown seeds grow into new plants. Certain seeds have hooks, stiff hair, or spines, which help in their dispersal. Now let us see the final way of dispersion of seeds.

Dispersion by explosion: When ripe, fruits of certain plants such as poppy, pea, and bean burst open in all directions, scattering the seeds in all directions. This phenomenon is called dispersal by the explosion. Here you can see a rare video of the dispersion of seeds by the explosion.

Read More: Reproductive Health And Adolescence: Reproduction In Animals