Cross Fertilization

What is Cross Fertilization?

To understand the cross fertilization meaning let us first begin by understanding fertilization. Cross fertilisation is a term referring to the reproduction among the plants. Fertilization is a sexual reproduction process in plants that occurs after pollination which is pollen production that represents the male contribution in the process and germination. The fusing of male gametes which are the pollen grains and female gametes ovum to generate a diploid zygote is known as fertilisation. It is a physicochemical reaction and it occurs only after the carpel has been pollinated. Since there are many types of flowering plants there are different types of fertilization as well. Let us go ahead and understand the definition and meaning of each type of fertilization and find answers.


Who Discovered Fertilization?

Strasburger discovered in 1884 that the vegetative nucleus and two male nuclei are discharged into the embryo sac by the pollen tube. He disclosed for the first time the fusing of one of the male nuclei with the egg nucleus in this landmark study on Monotropa hypopitys, demonstrating fertilisation in higher plants. And thus the world came to understand the possibility of the existence of many types of fertilization.


Fertilization and Its Types

  1. Self-fertilization - is the process of pollen being transferred to the stigma of the same flower and this is also referred to as autogamy.

  2. Internal Fertilization Definition -  Internal fertilisation is used by most sexual plants to reproduce. The ovary is where sperm and egg meet in plants. Pollen produces sperm, which is small and light and can travel by air or water. Plants, on the other hand, can develop sex organs that help sperm and egg meet.  

  3. External Fertilization - External fertilisation is commonly performed in water or a moist environment and fertilisation as the name suggests occurs outside the plant body. The moist environment helps to facilitate the movement of sperm or pollen to the ovum. Spawning is the release of eggs and sperm into the water and most of the external fertilization examples in plants include the ones that reside in water bodies. The benthic plants are the most common external fertilization examples and are prominently viewed and studied.

  4. Double Fertilization - Is where after the fertilization the zygote is divided into two cells as the female fuses with two male gametes and hence the name double which is an uncommon phenomenon. 

  5. Cross Fertilization - Pollen grains are transferred from one flowers’ anther to another’s stigma. This happens when two blossoms on different plants interact. And it happens often when flowers with diverse genetic backgrounds come together.

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This image explains the concept of cross-pollination that leads to cross fertilization in a simple manner.


Self- Fertilization Versus Cross Fertilization

The main difference between the self-fertilization and cross fertilization is the pollination process, which results in many different types of breeds and results and that keeps on changing as the years go by. 


Self Fertilization

Cross Fertilization

Pollination occurs within the flowers of the same plant.

Pollination between different flowers in different plants of the same species.

Also called autogamy.

Allogamy is another name for cross fertilisation. 

In progenesis, it leads to homogenous conditions.

Heterozygous condition is caused.

Inbreeding is caused.

Outbreeding is caused.

Declines the gene pool.

Maintenance of gene pool.

Limited amount of pollen grains production.

Abundance production of the pollen grains. 

Maturation of anther and stigma occurs at the same time.

A different amount of time is taken in maturing by both anther and stigma.

Very few pollen transfers occur.

There is a large amount of pollen transfer.

This process takes place even when the petals are enclosing the anthers and stigma.

The flowers need to be wide open for the agents to carry out pollination followed by fertilization. 

Only perfect flowers can carry out this mechanism of pollination leading to fertilization.

It is possible for both the perfect and imperfect flowers to carry out cross fertilization.

It increases uniformity in genetics while decreasing genetic variation.

The genetic variation due to this only increases and uniformity is declined. 


Benefits or Advantages of Cross Fertilization

  • Cross-pollination during the cross fertilisation process causes genetic recombination, which results in the emergence of new types.

  • Due to hybrid vigour, the offspring produced through cross-fertilization are healthy and stronger.

  • If only cross-fertilization is allowed or practised and self fertilization is avoided in a variety of crop plants like sunflower, mustard, and clover, they produce larger yields.

  • Among the types of fertilisation, this is the superior one because via this the disease resistant plant is originated.

  • Inbreeding depression can be avoided. 

Cross Fertilization Disadvantages 

  • Because cross fertilization is dependent on the agents, there is always some unpredictability.

  • From an economic standpoint, cross fertilization is not advantageous. Plants lose a lot of energy on numerous contraptions required for cross fertilization, and pollen grains are wasted in the process.

  • Despite its drawbacks, cross fertilization is nevertheless favoured by nature. In fact, plants have a variety of mechanisms to encourage cross fertilization while limiting self fertilization. The reason for supporting cross fertilization is mainly due to the production of healthier offspring.

Conclusion

Even though the agents carrying out the pollination process are the same as the wind, water, bees and other insects, bats and birds and other animals which are herbivores and graze on them, the consequences are so different for the pollination within the flowers or of the same plant and the flowers of different plants. Cross fertilization plays a vital role in maintaining the gene pool and creating hybrids that are disease resistant and from there on a healthy gene pool is created again. Even though the process takes a toll in every way the results are remarkable and worth all the energy and time consumed. Even though it is a natural process the man has been curating this phenomenon in recent years and the consequences are great despite the taxing ways of contemplating over which flowers of which plant must be crossbred. There is no other method that has been continued for so long and has evolved many healthy variants and there is no stopping this wonderful phenomenon anytime soon. 

FAQs (Frequently Asked Questions)

Q.1) Is Cross-fertilization Possible for Different Plants?

Answer.) Yes, the process of cross fertilization which basically involves cross pollination is of the basic idea that it is occurring in the different flowers of different plants. And the only thing to be considered is that the species of the plants chosen must not vary widely because in such a case of cross fertilization the results can be undesirable.

Q.2) What Is Not a Necessity for Cross Fertilization?

Answer.) Self-sterility refers to a bisexual flower's ability to produce viable offspring. Allogamy necessitates self-fertilization and is not a requirement for it. The flowers need not be perfect for this process. 

Q.3) What is the Negative Effect of Cross Fertilization?

Answer.) The negative effect of the process of cross pollination and fertilization can be stated that with a drastic increase in the harvest that can be tiring. And that is the reason why cross pollination is not always a good idea because it increases the harvest too much. Fruits would remain small, and the branches would be prone to breaking off. Furthermore, trees that bear an excessive number of fruits will age and die only within a few years, exhausting and deteriorating the health and goodness of the mother plant.