Fertilization in Plants: Definition, Process, Types, Steps and Diagram

What Is Fertilization In Plants?

In flowering plants, fertilization is a process through which the union of male and female gametes takes place to form a zygote. This is done immediately after pollen grains from anther bag attach to the plant stigma. It will now trigger the formation of seeds and fruits. Fertilization is a prerequisite for any reproductive success of flowering plants. It ultimately results in creating genetically varied offspring that foster the adaptability and evolution of plant species.

In addition, it allows for seed and fruit to be generated, thus the continuation of plant species, which provides a means to sustain ecosystems and agricultural output. The fertilization process begins with the germination of the pollen grain within the stigma and continues to the development of a pollen tube that extends itself through style and reaches the ovule. One male gamete unites with the egg cell, while the other combines with two polar nuclei to form the endosperm—thus, seeds initiate a double fertilization event, which later forms a new plant.

Pollination

Pollination may be defined as the transfer of pollen from the male anther to the female stigma of a flower; it is a process necessary for fertilization and later seed production.

Definition And Types Of Pollination

The types of pollination are:

Self-Pollination

Self-pollination is the fertilization of ovules through the flower's pollen or pollen from another flower in the same plant. This is a normal process in most plants, which brings about less genetic variation since the offspring will genetically be more like the parent plant.

Cross-Pollination

Cross-pollination is a process by which pollen is moved from one plant's anther to another plant's stigma, both of different plants of the same species. In this method, the diversity of genetic material in the resultant offspring is high since they obtain their genetic material from two separate parent plants.

Mechanisms Of Pollination

Biotic Agents (Insects, Birds)

Insects such as bees and butterflies and birds such as hummingbirds are common biotic agents of pollination. As they move from flower to flower in search of nectar, pollen is transferred from one part to another.

Abiotic Agents (Wind, Water)

These include wind and water. Plants that are wind-pollinated produce vast amounts of light-weight pollen that can travel long distances in the air. Water pollination, which is much less common than the other two, involves pollen being transported by water currents in some aquatic plants.

Process Of Fertilization

Fertilisation in plants is a multi-step process that leads to seed formation.

Pollen Grain Germination

When a mature pollen grain lands on a stigma of the same species, it germinates. A pollen tube develops that grows towards the ovule down the style.

Growth of Pollen Tube

The pollen tube gradually grows through the style tissues till it reaches the ovule in the ovaries.

Entry of Pollen Tube into Ovule

Entry of Pollen Tube inside Ovule It enters the ovule through an opening called the micropyle.

Double Fertilization

Double Fertilization In this unique feature of flowering plants, two sperm take part in fertilization.

Syngamy (Fusion of Sperm and Egg)

Syngamy (Fusion of Sperm and Egg) One sperm fertilizes the egg cell to form a diploid zygote which will grow into an embryo.

Triple Fusion (Fusion of Sperm with Polar Nuclei)

The second sperm cell fused with polar nuclei of the ovule gives rise to a triploid cell which develops into endosperm and the nourishment of the growing embryo.

Post-Fertilization Changes

The post-fertilization changes are explained below-

Formation Of Zygote

The fertilized egg cell which is the zygote undergoes several divisions and develops into an embryo.

Development Of Embryo And Seed

The ovule is developed into a seed, containing an embryo, endosperm, and seed coat.

Formation Of Endosperm

The triploid endosperm cell undergoes several divisions and develops into nutritional tissue that nourishes the developing embryo within the seed.

Transformation Of Ovary Into Fruit

After fertilization, the ovary changes into a fruit. Fruit is a structure that houses and protects the seeds and enables upward dispersal of seeds.

Types Of Fertilization

The types of fertilization are listed below-

Porogamy

In porogamy, the pollen tube enters through the micropyle into the ovule, and it is the type of fertilization that is most common in plants.

Chalazogamy

In chalazogamy, the pollen tube enters through the opposite pole of the micropyle of the ovule, that is, directly through the chalaza.

Monogamy

Here, the tube enters the ovule through the integuments.

Recommended video on "Fertilization in Plants"