Table of Contents
What is Pollination?
Pollination is the transmission of gametes from males (pollen grains) in plants from the male reproductive part (anther) to the female reproductive part (stigma).
Pollination is the basis of fertilization in plants because it allows for the movement of gametes within plants that otherwise are not mobile. Pollination can be resulted by different pollinators like insects, wind, water and even animals. Sometime, even plants could cause pollination through self-pollination. It is most common when flowers are closed. Gametes transfer is usually inside the species, however when the transfer happens between species, hybrids will develop.
In non-flowering plants such as cycadsthe pollen gets trapped in the fluid released by the ovule when the Ovules are exposed. In flowers, however, the ovules are enclosed in pistils, a form of structure that consequently require pollination by external agents. Pollen grains are dehydrated to decrease their weight to allow them to be easily transferred from one flower to the next. The hydration and activation process of pollen grains occurs when they touch the stigma prior to the development of the tube that is pollinated. According to the study, pollination can be caused by both biotic as well as Abiotic agents. Abiotic agents comprise wind, water and rain, while biochemical agents include birds, insects and even animals.
Different plants could have different pollination strategies using a mixture of abiotic and biochemical methods. Pollination can be achieved through either of two methods that are self-pollination or cross-pollination. Self-pol occurs when pollen grains are transferred from an anthers of one flowers to the stigma of a different flower from similar plant. Self-pollinating plants usually have carpels and stamens that are similar length that are developing at the same time.
Cross-pollination involves an exchange of pollen grain from one anther of a bloom to a flower from another plant in identical species. Plants that undergo cross-pollination have mechanisms that prevent self-pollination, which is a feature of the reproductive organ that develops at various phases of their life cycle. The colour of the flower and nectar that is produced are significant factors that aid in pollination through attracting animals and insects. Additionally, other modifications such as the reduction in weight and water-resistant spores are additional changes that aid in pollination. Pollination examples can be seen by the pollination process of Yucca flower by moths as well as self-pollination of wheat and barley.
What is Fertilization?
Fertilization is an aspect of sexual reproduction, which follows the copulation of animals as well as pollination of plants. For plants, fertilization occurs after pollination. It begins with watering and activation of pollen grains, as well as the creation of the tube that is known as the pollen. Rehydration stops the premature germination of pollen inside the anther. In the process of rehydration the pollen’s plasma membrane is restored to its original structure, and activation is the process of forming filaments of actin which eventually result in the formation of an anther tube.
Since the male gamete in plants is not motile and does not move, it relies to the pollen tube to facilitate their transfer to the ovary from the stigma. The pollen tube enters into the stigma and then expands along with the extracellular style matrix, ultimately getting to the ovary. It then enters the ovule via the micropyle, and the pollen tube explodes inside the embryo sac and releases the embryo’s sperm. Gynosperms are different, in that the development of the pollen tubes doesn’t happen because the ovules are not encased by the ovary.
Angiosperms in turn undergo double fertilization in which two pollen tubes fertilize two cells inside the ovary. One sperm fertilizes egg cell that is haploid, resulting in a diploid-like zygote. However, the second sperm forms an embryonic cell that has two haploid polar nuclei which results in a triploid. The triploid grows into an endosperm which feeds the zygote in the ovary. As with pollination, fertilization within plants could also involve the result of self-fertilization and cross-fertilization. Most often, self-pollination results into self-fertilization and cross-fertilization result in cross-fertilization.
Fertilization in animals however, may occur through external or internal processes. When internal fertilization is performed, fertilized sperm enters into the female’s body via copulation , and it is able to fuse with the egg cell. External fertilization occurs when eggs are placed on the surface of the female. They are then fertilized with sperm cells released from females over eggs externally. Therefore fertilization is an inner process that takes place inside the tissues of living organisms, both plants and animals. Since it’s an internal procedure, it does not require external elements to complete it. Fertilization is also a common place in all kinds of plants, from non-flowering, flowering, to primitive species like bryophytes and the thallophytes.
Difference Between Pollination and Fertilization – Pollination vs Fertilization
|Basis for Comparison||Pollination||Fertilization|
|Definition||Pollination refers to the transmission of gametes from males (pollen grains) in plants from the male reproductive part (anther) to the female reproductive part (stigma).||Fertilization is the merging haploid male female gametes to create an zygote that is diploid to begin the creation of a new species.|
|The nature of the process||Pollination is an actual physical process.||Fertilization is a genetic as well as biochemical process.|
|The type of procedure||Pollination is an external procedure that takes place outside of the plant’s body.||Fertilization is an internal procedure that occurs within the components of the plant.|
|Occurs in||Pollination is only found in flowers of plants or distinct male and female reproductive organs.||Fertilization can be found in all kinds of animals and plants that reproduce through sexual reproduction.|
|Time||Pollination is the primary ingredient for fertilization in plants , and therefore is a prerequisite for fertilization.||Fertilization takes place following pollination.|
|External elements||Pollination is influenced by external factors, both biotic and abiotic.||Fertilization is not influenced by external influences.|
|Involves||Pollination is only movements of pollen grains, or those male gametes.||Fertilization is a process that involves male and female gametes.|
|Pollen tube||There is no pollen tube formed when pollination occurs.||The process of fertilization for plants takes place through the creation in the pollen tube.|
|Types||Pollination can be achieved through two kinds of methods: self-pollination and cross-pollination.||Fertilization in plants can be classified into three types: Chalazogamy, Porogamy, and Mesogamy|
|Mechanism||Pollination is a result of the use of pollination substances like air, water, insects and even animals.||Fertilization is a result of activation, hydration and the formation of pollen tubes.|
|Pollen grains||The pollen grains undergo dehydration to reduce their mass to facilitate the process of pollination.||Pollen grains undergo rehydration following getting to the stigma, which starts the process of forming the pollen tube.|
|Flowers are involved||Pollination might occur between two different flowers.||Fertilization is always happening within a single flower.|