Sexual Reproduction in Plants

Introduction

Plants are a necessary part of survival on this planet. Different plants multiply in different ways. One of these is, multiplication through reproduction. Reproduction is one of the main life processes. It is defined as the process of production of offspring from the parents.

Though plants and animals both have male and female parts, still, plant kingdom and animal kingdom are very different when it comes to reproduction. Sexual reproduction in plants is very complex and diverse.

Sexual reproduction is not unique to animals, plants also use this process to reproduce. Humans reproduce by intercourse, whereas plants use pollination to produce offspring. 

The reproductive part in plants is flowers. So, that’s why we call it reproduction in flowering plants.

Flowers have stamens as male reproductive part and pistil as female reproductive part. The pistil consists of stigma, style, and ovary. Plants can reproduce in two ways, i.e., sexually and asexually.

Types of Reproduction in Plants

Plants have two types of reproduction, i.e., sexual and asexual.

❖ In sexual reproduction, parent plants produce offspring by the fusion of gametes. In this, the offspring are genetically very different from their parents.

The two fundamental processes in this are:

1. Meiosis reduces the number of chromosomes and changes the arrangement of genes.
2. Fertilization restores a complete diploid number of the chromosome.

In these two procedures, plants alter generations, different multicellular phases, gametophyte, and sporophyte. If we look at the sexual reproduction in plants, examples will be corn, cucumber (unisex flowers) and petunia (bisexual flower).

❖ In asexual reproduction, parents produce offspring without the fusion of gametes. In this, the offspring are very much identical to the parent plant. This type of reproduction occurs through budding, fragmentation, binary fission, regeneration, spore formation, and vegetative propagation

Only one parent is required because fusion of male and female gametes doesn’t occur. Vegetation and agamospermy are two fundamental forms that occur in asexual reproduction.

If we further look into the asexual reproduction in flowering plants, they have two main types of reproductions: –

1. Vegetative reproduction– This type of asexual reproduction results in the formation of new plant individuals without any production of seeds or spores.
2. Apomixis– This type of asexual reproduction takes place without fertilization. The name itself is self-explanatory as “Apo,” meaning away, and “mixis,” meaning mixing. Generally, reproduction happens through seeds (called clonal reproduction).

Pollination

It is a bit complex when someone asks to explain sexual reproduction in plants, but if we take a closer look at it, it is pretty interesting and straightforward. The gametes from one flower fall to the gametes of the opposite sex part of the flower. This is called pollination.

Pollen grains are transferred from male reproductive organs (anther) to female reproductive organs (stigma). The basic nature of plants, which is to create offspring, is followed by the plants to propagate their next generation. A question might have come to your mind: how do the pollen travel from one flower to another? The forces of nature and nature itself help the pollen move.

– When we talk about insects, they are the master source of transporting pollen grains to another flower, and hence they are called pollinators. It is usually dependent on the regular activity of the insect/animal on that particular flower.

– The forces of nature, for example, the wind, is a major factor that helps in pollination. Wind directs the pollen grains from the anther to fall off and take with it to the stigma of the other flower.

In total, there are many ways where reproduction in flowering plants can take place eventually without any disturbance. A major factor is that the seeds can only be produced when pollen is transferred in between the flowers of the same species (here, the species is to be defined as the number of species which can altogether interbreed but, due to some biological factors, can not interbreed with the members of other species).

Types of Pollination

We have already discussed the types of sexual reproduction in plants. Now, we will further clarify what types of pollination are and how they take place in the process of reproduction in flowering plants around us. There are two major types of pollination in plants. The first one is-

Self-pollination– As the name defines itself, the pollination in this typically happens in the same plant or flower. The pollen in the flower is transferred to the stigma of the same plant. It can be autogamy, when pollen from the anther lands on the stigma of the same flower.Or it can be geitonogamy when the pollen grains from the anther lands on the stigma of another flower on the same plant.

Cross-pollination: When the pollen grain from the anther of another flower lands on the stigma of some other flower, we call it cross-pollination. This process has one great advantage; it brings many variations in plants.

Pollinating Agents

They are the agents that help in transfer of pollen grains from the anther to the stigma of the flower.They can be:

Abiotic Agents -Air and water

Biotic Agents-Insects,birds ,animals

Air -Plants pollinated by air have pollen which are light,small in size.Stigma is  well exposed and sticky.

Water-Plants pollinated by water have pollen which have a mucilaginous covering over the pollen which prevents them from getting wet.

Animals-Plants pollinated by animals have flowers which are brightly coloured,have nectar and fragrance.

Conclusion

Plants can reproduce sexually as well as asexually. The reproductive organ in the plant is a flower. Plants reproduce by the process known as pollination. Pollination also consists of two types: i) Self- pollination ii) Cross-pollination. Now, pollination is the transfer of pollen to the pistil, after which it gets transferred to the ovary, then makes the ovules mature, after which it turns into a seed.

The transfer of pollen is done by an agent called pollinators such as insects, wind, water, etc. Though plants and animals both have male and female parts, still plant kingdom and animal kingdom differ greatly when it comes to reproduction. Sexual reproduction in plants is very complex and diverse.