Before jumping into pollination types, we should first learn about the concept of pollination.
The basic goal for every living being on our planet is to have offspring.
Plants don’t reproduce like us but that doesn’t mean they don’t. Their reproduction is termed asexual reproduction. Plants reproduce by generating seeds. In producing a new plant, the genetic information needed is found in seeds.
The tool that a plant uses to create a seed is a flower. Seeds can only be generated by one method that is when the same species of flowers transfer the pollen to each other. The whole act of transferring pollen grains from male anther to female anther is termed pollination.
All plants need to propagate for the growth and survival of their species. Plants reproduce by pollination. Flowers help plants to propagate. A flower is the most beautiful part of the plant and the one responsible for the process of pollination. Pollination is the transfer of pollen grains produced by the flower from its anther to the stigma of the same or different flower. This process takes the help of natural agents like birds, insects, and biological agents like the water and the wind. These are known as pollinating agents. They are also called “pollinators”.
Pollination is the result of the unintentional activities of an animal on a flower. When the pollinator eats and Collects the protein along with other nutrients from the pollen or when it’s sipping the nectar from the flower, that time pollen grains attach themselves to the body of the pollinator. When that animal goes to the other flower, pollen often falls on the stigma of that flower and results in the successful reproduction of the flower.
After this, pollen from the first flower’s anther deposits on the stigma of flower number two. Pollen most likely germinates on the stigma of the flower which states that it formed a “pollen tube” on the surface of the stigma that is sticky and then they shift to grow in the ovule of the plant.
The flower is fertilized successfully and the seeds, fruits have started growing.
There could be a possibility that the plant is fertilized partially, which means the seeds and the fruits may not grow fully.
This results in the plant failing to pollinate and won’t grow at all.
Pollination of the pollen grains can occur in the same flower or in two different flowers. Based upon the location of transfer of the pollen, pollination is of the following two types.
We will now study these two methods of pollination and what is the difference between self-pollination and cross-pollination.
Self-pollination happens on a single flower. It is the primary method of pollination. It involves the transfer of pollen grains from the anther to the stigma part of the same flower. The process is straightforward and quick, and easy to understand, as well.
In this process, the pollen grains from the anther or the flower's male reproductive structure get transferred to the stigma or the female reproductive structure of the same flower or of another flower on the same plant. The pollen grains are carried by the wind, water, or animals.
Plants like orchids, oats, legumes, peas, sunflowers, peanuts, peaches, potatoes, and wheat follow self-pollination. In the case of self-pollination, the same plant's genetic material is used to form gametes, and finally, the zygote. Hence, self-pollination leads to the production of plants that do not have genetic diversity.
Self-pollination occurs in flowers when both the reproductive parts, the stamen and the carpel, mature at the same time. This method does not require any pollinating agents or any nectar and pollen to attract insects or birds.
Self-pollination consists of two types: autogamy and geitonogamy.
When the transfer of pollen is done to the stigma of the same flower, it is known as autogamy.
When the transfer of pollen happens from another of flower one to the stigma of flower two on the same flower with one gymnosperm, it is known as geitonogamy.
Cross-pollination is the second and more diverse form of pollination. It occurs when there is a transfer of pollen grains from the anther of one flower to the stigma of another flower. The destination flower is a different flower of the same species. This method of pollination leads to an increase in genetic diversity. It is because the genetic information from different flowers gets shared and crossed. It results in the creation of unique offspring. In this case, the reproductive process takes place in different plants.
Cross-pollination is also known as heterogamy. It is a type of pollination where pollen grains which are sperm-laden get transferred from the flowers of plant one to the second flowers which are egg-bearing.
It is found in both flowering plants and cone-bearing plants.
Cross-pollination can be carried out by wind as well as bees and other birds or animals. Insects cross-pollinate many fruit-bearing plants like apples, strawberries, raspberries, grapes, plums, and flowers like tulips and daffodils. Wind pollination can be observed in different grasses, maple trees, and dandelions.
Have you ever wondered how self-pollination is different from cross-pollination? Self-pollination and cross-pollination are common pollination methods, but there is a vital difference between self-pollination and cross-pollination. The diagram below shows this.
Self-pollination and Cross-Pollination Diagram
(Image will be Updated Soon)
You can see that the pollen from the anther of the flower gets deposited onto the stigma of the same flower in the first flower.
In the second flower, you can see how the pollen from another flower gets deposited on its stigma.
This picture clearly shows the self-pollination and cross-pollination differences.
Now we will differentiate between self-pollination and cross-pollination with the help of the table below.
Butterflies prefer flowers with flat petals where they can easily land.
Hummingbirds like long and tube-shaped flowers in red, pink, or fuchsia colors.
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1. How is Self-pollination Useful?
In the case of self-pollination in plants, the pollen from the anther gets deposited on the stigma of the same flower or different flowers of the same plant. Due to this, the plant does not need to generate a large amount of pollen or nectar. The process is quick and there are fewer chances of its failure.
The advantages of self-pollination are as follows.
Pollination is guaranteed for surety.
Less pollen quantity needs to be generated.
It preserves parent flower characteristics.
No external factors like wind or pollinating insects are required.
Requires fewer flower characteristics like large shapes, color, or scent.
However, there are some disadvantages to self-pollination as well.
No new plant varieties can be formed.
Genetic variation remains homogeneous.
The plant vitality decreases over time due to continuous self-pollination.
Plant immunity and sustainability also decreases.
Self-pollination mostly occurs in peas, soya beans, peanuts, orchids, and sunflowers.
2. How is Cross-pollination Beneficial for a Plant?
In the case of cross-pollination, the pollen from one flower gets deposited on a flower of a different plant. This can lead to the production of unique plant varieties as two different plants of the same species, or different species are involved. Cross-pollination often leads to more diverse genetic variation. It leads to the development of new plant species.
Cross-pollination comes with its benefits, which are as follows:
Offsprings have genetic variety and diversity.
Species generated have a higher rate of survival and sustainability.
The quality of the new offspring is enhanced.
Offsprings inherit the best qualities from both the parent flowers.
At the same time, cross-pollination comes with its disadvantages as well and they are as follows.
Two separate parent plants are needed for this type of pollination.
Pollinating agents are required.
Less guarantee of success of pollination.
There is a need for the production of large amounts of pollen.
Flowers need to be large, showy, colorful and scented.
3. What are the methods to prevent cross-pollination?
When you want to save the seeds, it becomes very important to save the crops which aren’t self-pollinating, from cross-pollinating. The methods used to prevent cross-pollination are discussed below:
The first basic step towards this is keeping the plants away from each other. Distance by isolating the plants is a way that works really well and makes cross-pollination very hard.
Isolation by distance works when there’s plenty of room available. When there is limited space, this method does not work. The containment method is used then. It means keeping the plants physically isolated by using isolation tents.
Bags made of quick-drying known as blossom bags are used to prevent cross-pollination. It means to cover the individual flower or a branch in these blossom bags.
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4. What are the disadvantages of self-pollination and cross-pollination?
As you know, it happens on the same flower, the mixing of genes never happens. Because of this, not a new feature or character gets created and introduced to their offspring.
Self-pollination is known to minimize the vitality of the race because no new trait gets added.
The new offspring’s immunity towards diseases seems to reduce because of no new character addition.
The wastage of pollen grains is very high which is needed to get produced to provide the surety of fertilization.
The chances of the subtraction of good qualities are very high and unwanted things get added because of the genes recombination.
5. Explain the different types of cross-pollination?
Few of the many types are discussed below:
The flowers which are pollinated by the means of water are known as Hydrophilous flowers. They are very small in size. They have no fragrance or color. This pollen is adapted to its ability to float in water.
The agents of pollination like humans, animals and birds come under Zoophilous flowers. The pollen of these flowers is created in a way so that they stick on the body of animals and make it easy for the pollen to travel from one plant to another.
The pollen grains which are very light to carry, which do not stick and sometimes are winged, are known as Anemophilous flowers.