Fertilisation

The whole process of fertilisation in plants involves different parts of the plant such as the Stalk, Calyx, Corolla, Androecium, Gynoecium. This whole process begins after the fertilisation of the male and female gametes occurs. This article discusses fertilisation and defines fertilisation in detail. 

Definition of Fertilisation

To define fertilisation the answer would be, it is the process in which the male gamete released from the stamen and the female gamete released from the pistil of the plant comes into contact is called fertilisation. Fertilisation is a physicochemical process. The process of fertilisation takes place in the zygote and this zygote turns into a seed after it is matured.        

Parts of the plant involved in Fertilisation

• Stalk-The part of the plant which attaches the flower to the stem of the plant. The stalk is also known as pedicel. The stem is attached at the end of the stalk. The flower is attached to the stalk at the upper part. This junction of the flower and the stalk is called the Thalamus. This Thalamus is attached to four whorls of the plant. The four whorls are-

• Calyx- Calyx is the outermost whorl. This is a green leaf-like structure, also called the sepal. The sepal can be of different colours.

• Corolla- The second whorl is the Corolla. This part of the flower consists of the petals. These petals make the flower look attractive which attracts the insects and these insects help in the process of pollination.

• Androecium- The male reproductive part of the flower is the androecium. This part of the flower consists of the stamen. A stamen is a tube-like structure that is attached to a broad anther at the tip of the stamen. This anther contains the male gametes or the pollen grains which take part in the fertilisation process.

• Gynoecium- Gynoecium is the female reproductive part of the plant. The Gynoecium is the innermost whorl in the plant. This part of the plant consists of the pistil, made up of an ovary at the bottom, and has a tube-like structure called style attached to the stigma at the top. The pollen gets attached to the stigma and reaches the ovule through the tube-like structure. The pollen fertilises the ovule cell in the zygote. 

Process of Fertilisation

The stamen of Androecium contains small yellow grains called pollen grains. These pollen are collected on the stigma after pollination occurs. The stigma extends like a long tube to the ovary. This long tube is called style. The collected pollen reaches the ovary through the style. Here the pollen (male gamete) comes in contact with the ovule cells (female gamete). 

To define fertilisation, the above-mentioned process can be a detailed illustration of the process. The whole process of fertilisation can be divided into four steps:

• Pollination: The process by which the pollen grains from the stamen are carried away by insects, wind, or water to the stigma of a pistil is called pollination.

• Germination: The formation of the pollen tube of the pistil which forms a passage for the sperm to enter the ovary, this process is called germination.

• Ovule Penetration: Ovule penetration is the process in which the male gamete (pollen grain) after it enters the ovary, comes in contact with the female gamete (ovule).

• Fertilisation: When the pollen enters the ovule it fertilises the ovule cells or the egg. This process is called fertilisation.

Types of Fertilisation

To define fertilisation, we need to discuss the types of fertilisation. The different types of fertilisation are:

• Porogamy 

This is the most common type of fertilisation in angiosperms. In this type of fertilisation, the pollen grain reaches the ovule cells through the style. In this type of fertilisation, the pollen tube reaches the ovule through the micropyle. This type of fertilisation can be seen in plants like a lily.

• Chalazogamy

This type of fertilisation is not very common in angiosperms or flowering plants. This type of fertilisation can be seen in certain species of plants like Casuarina. This type of fertilisation is different from porogamy. It is different in the way that, in porogamy the pollen tube enters the ovule through micropyle, but in this type, the pollen tube enters the ovule through chalaza. This type of fertilisation can be seen in plants like Betula, Casuarina, etc.

• Mesogamy 

In this type of fertilisation, the pollen tube enters the ovule through integuments or the middle part of the ovule. This type of fertilisation can be commonly seen in cucurbit plants like pumpkin, gourd, bitter gourd, etc.

Double Fertilisation

In this type of fertilisation, the female gametes are fertilised by or fused with two male gametes. In this type of fertilisation, one male gamete fuses with the zygote which produces the egg. The other male gamete fuses with two polar nuclei which form the endosperm. All the angiosperms or flowering plants go through double fertilisation. 

Conclusion

I hope by now you know what fertilisation is and the types of fertilisation. Now you know which part of the plant takes part in the fertilisation. This article focuses on the process of fertilisation in detail and tries to define fertilisation. However, fertilisation is different. What happens during human fertilisation is the sperm (male gamete) the sperm travels to the oviduct and fertilises the egg produced from the ovary. Fertilisation is the fusion of the nuclei of the male gamete and the nuclei of the female gamete.