[Biology Class Notes] on Are We Not Lucky that Plants Reproduce Sexually? Pdf

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.

1. 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.

2. Hydrophily – pollination by water. Pollen grains are carried away by water currents and cause pollination in aquatic as well as many terrestrial plants.

3. 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.