Sexual Reproduction in Plants

Sexual reproduction in plants is the process of fusion of male and female gametes (sex cells) results in the evolution of a diploid zygote and develops into a new organism. Hence this sexual type of reproduction brings variation and evolution because offspring created differ from their parents genetically. The result of this flowering process is fruits and seeds and such seeds then grow into new plants. Sexual reproduction has two main phases pollination and fertilisation. Following fertilisation, fruit and seeds are formed within the flower.

Parts of a flower

can be classified as unisexual or bisexual and it depends on the fact if it contains stamen or pistil. Flowers are the location of amphimixis in flowering plants.

• Calyx: It is the topmost whorl of the flower. It is composed of leaf-like green sepals. Sepals primarily won’t protect flowers.
• Corolla: It is the second whorl of flowers and consists of several petals. Birds and insects are attracted to its colours, which helps with pollination.
• Androecium: it is the third whorl of a flower that has stamens. Stamen is a male sex organ of a flower. Each stamen is formed from the filament and another. Anthers resemble sac-like structures and produce and store pollen in them. Filament supports the anther.
• Gynoecium: this is often the last and fourth whorl of the flower that has pistil or carpel. The pistil is a female sex organ of the flower. Each pistil consists of the ovary, style, and stigma.
• The stigma is the foremost part of the flower while the style is the long tube that joins the ovary with the stigma. In each ovary, there are many ovules present. In the ovary, seeds are produced in plants.

Microsporogenesis

The result of the microsporogenesis process is the formation of male gametes. The pollen cell present within the anther undergoes meiosis and forms microspores.

Megasporogenesis

The result of megasporogenesis is the evolution of female gametes referred to as megaspores or eggs. The megaspore cell produces four haploid megaspores. Ovules are called the megasporangium.

Pollination and fertilisation of plants

Pollination is an important part of the life cycle of a flowering plant. It is a kind of sexual reproduction in plants, leading to seeds that ultimately grow into new plants. The flower is a part of flowering plants and it contains all the specialized parts required for sexual reproduction.

Zygote formation takes place when pollen grains with male gametes fuse with eggs in ovules. Plants have both gametes, which contain half the  number of chromosomes for that plant species. Male gametes are found inside the pollen grains on the male reproductive part anthers. Female gametes are in the ovules of a flower. 

Pollen does not come from the anthers to the ovules on its own, so pollination depends on other things to move the pollen. The wind or insects and birds take pollen from the anthers and carry it to the female part stigma. Flowers have different colours, shapes, and smells, and sometimes sugary nectar and nutritious pollen can encourage insects to go to and pollinate them.

There are two types of pollination based on where the pollen lands.

1. The transfer of pollen between the anther and the stigma of the same flower is called self-pollination.
2. Pollen moves from the stigma of one flower to another flower on the same species or distinct species of the same plant, resulting in cross-pollination.

Pollen grains migrate to the stigma, where they release male gametes, which combine with the egg to produce a zygote thus fertilisation generally describes the fusion of haploid gametes to initiate the event of a replacement diploid organism.

Below are the collective steps involved in pollinating and fertilising a flowering plant.

1. After pollen has landed on the stigma, it grows a plant part down through the design to the ovary.
2. The nucleus of the pollen grain travels down the pollen tube and fertilises the nucleus in the ovule.
3. The fertilised ovule develops into a seed. The seed contains an embryo, which has genetic material from its parents. The ovary develops into a fruit.

In some cases in angiosperms, a male gamete wires with an ovule having two cores, this is called double fertilisation. One male gamete can form the zygote, but the opposite one fuses with diploid polar nuclei to make an endosperm. The zygote develops the longer-term plant, and endosperm helps in nutrition for the embryo. An example of endosperm is tender coconut water. 

Conclusion

Reproduction is important as it helps in the continuance of the species. The process of sexual reproduction in flowering plants has its advantages. The seeds used to develop plants are the result of this sexual reproduction only. Sexual reproduction in plants gives us every single fruit we eat. Pollination happens as a result of many natural pollinating agents. To make a zygote, the pollen grain should fuse and do pollination. Certainly, pollen grains of some flowers have an exceptional fragrance that interests the pollinating agents that will help in pollination.