Step into the Fascinating World of Plant Pollination
Pollination is essential for plant reproduction, ensuring the transfer of pollen grains from the anther (male part) to the stigma (female part). First described in detail by Christian Konrad Sprengel in the 18th century, pollination underpins agriculture, horticulture, and the survival of many wild plant species.
Plants can reproduce using two major pollination types: self-pollination and cross-pollination. In this comprehensive guide, we will explore the difference between self pollination and cross pollination, discuss what are the three difference between self-pollination and cross pollination, provide example of self-pollination and cross pollination, include a cross pollination example in detail, and share fun activities to reinforce your learning.
Overview of Pollination
Definition: Pollination is the process of transferring pollen grains from the anther to the stigma, enabling fertilisation and the production of seeds.
Importance: Promotes genetic information transfer, ensures plant survival, and maintains biodiversity.
Agents: Various vectors like wind, water, insects (e.g., bees, butterflies), birds, and sometimes small mammals.
Also, read Types of Pollination
What is Self-Pollination?
Self-pollination occurs when pollen from the anther is deposited onto the stigma of the same flower or another flower on the same plant. This can happen in two ways:
Autogamy: Pollen moves from the anther to the stigma of the same flower.
Geitonogamy: Pollen transfers from one flower to another flower on the same plant.
Common Examples of Self-Pollination
Legumes: Peas, peanuts, and beans frequently self-pollinate.
Cereals: Wheat and oats often rely on self-pollination.
Ornamental Plants: Certain orchid species and sunflowers can self-pollinate.
Stone Fruits: Some peach varieties show a high rate of self-pollination.
Unique Features of Self-Pollination
Requires no external pollinators: Useful in areas with fewer pollinating insects or unfavourable climates.
Encourages homogeneity: Offspring are genetically very similar, as the same genetic material is shared.
Limited pollen production: Because there is less need to attract external vectors.
Simultaneous maturity: Anther and stigma typically mature together, ensuring successful pollination.
What is Cross-Pollination?
Cross-pollination happens when pollen from one plant’s flower is transferred to a flower on a different plant of the same species. This process usually involves pollinating agents such as wind, insects, birds, or other animals.
Cross Pollination Example
Wind-Pollinated Plants: Grasses like wheat and maize, maple trees, and dandelions often rely on wind to carry pollen between flowers on separate plants.
Insect-Pollinated Plants: Fruits like apples, pears, plums, strawberries, and decorative blooms like tulips and daffodils depend on insects to transport pollen.
Unique Features of Cross-Pollination
Greater genetic variation: Encourages outbreeding, which increases adaptability and resilience in changing environments.
Requires external vectors: Wind, water, insects, or animals typically carry pollen over some distance.
High pollen production: More pollen is produced to compensate for loss during transfer.
Different maturity times: Anther and stigma frequently mature at separate intervals to promote cross-pollination over self-pollination.
Difference Between Self Pollination and Cross Pollination
If you are searching for what are the three difference between self-pollination and cross pollination, below is a more comprehensive comparison:
Additional Insights and Unique Facts
Mechanisms Preventing Self-Pollination: Some flowers have physical or chemical barriers (self-incompatibility genes) to stop their own pollen from fertilising them, promoting genetic diversity.
Impact on Crop Breeding: Cross-pollination is often exploited by plant breeders to create hybrid crops with desirable traits like disease resistance, better taste, and higher yield.
Environmental Factors: Humidity, temperature, and availability of pollinators significantly affect both self and cross-pollination success rates.
Also, read Parts of a Flower and Structure of a Flower
Quick Quiz: Test Your Pollination Knowledge
Which scientist is credited for first describing the process of pollination?
Name one major cross pollination example involving insects.
Mention one key example of self-pollination and cross pollination each.
State what are the three difference between self-pollination and cross pollination you find most important.
Why do cross-pollinating plants produce more pollen than self-pollinating plants?
Check Your Answers Below
Christian Konrad Sprengel.
Apples (bees often pollinate them).
Self-pollination: Wheat; Cross-pollination: Daffodils.
(i) Genetic diversity vs. genetic similarity, (ii) dependence on pollinators vs. no dependence, (iii) large vs. small pollen production.
To increase the probability of successful fertilisation, as pollen can be lost during transit via wind or insects.
FAQs on Self vs Cross Pollination: Exploring Key Differences
1. What is the main difference between self-pollination and cross-pollination?
The primary difference lies in the source of the pollen. In self-pollination, pollen is transferred from the anther to the stigma of the same flower or another flower on the same plant. In cross-pollination, pollen is transferred from the anther of a flower on one plant to the stigma of a flower on a different plant of the same species.
2. What are some common examples of plants that use self-pollination and cross-pollination?
Common examples include:
- Self-Pollination: Plants like peas, wheat, oats, and peanuts often rely on self-pollination. They typically have flowers that do not need to be showy to attract pollinators.
- Cross-Pollination: Plants like apples, plums, daffodils, and maize depend on cross-pollination, which is facilitated by agents like insects or wind.
3. Why does cross-pollination result in greater genetic variation in offspring?
Cross-pollination leads to greater genetic variation because it involves the fusion of gametes from two genetically different parent plants. This process, also known as allogamy, introduces new combinations of genes and alleles in the offspring. This increased diversity enhances the population's ability to adapt to changing environmental conditions and avoid inbreeding depression.
4. How can you identify if a flower is adapted for cross-pollination by insects versus by wind?
You can identify the pollination method by observing the flower's characteristics.
- Insect-pollinated (Entomophilous) flowers are typically large, colourful, fragrant, and produce nectar to attract insects.
- Wind-pollinated (Anemophilous) flowers are usually small and inconspicuous, lacking bright colours, nectar, or fragrance. They produce large amounts of light, non-sticky pollen and have large, feathery stigmas to effectively trap airborne pollen.
5. What are 'outbreeding devices' and how do they promote cross-pollination?
Outbreeding devices are mechanisms in plants that discourage or prevent self-pollination to promote genetic diversity. Key examples as per the NCERT syllabus include:
- Dichogamy: The anther and stigma mature at different times.
- Self-incompatibility: A genetic mechanism that prevents pollen from fertilising ovules of the same flower or plant.
- Production of unisexual flowers: The plant bears either male or female flowers, making self-pollination impossible.
6. What is the key difference between autogamy and geitonogamy in self-pollination?
Although both are types of self-pollination, the key difference is the flower involved. Autogamy is the transfer of pollen from the anther to the stigma of the same flower. Geitonogamy is the transfer of pollen from the anther of one flower to the stigma of another flower on the same plant. While geitonogamy is functionally a type of cross-pollination (as it often requires a pollinating agent), it is genetically identical to autogamy since the pollen comes from the same parent plant.
7. What are the evolutionary advantages of self-pollination for a plant?
Despite leading to less genetic diversity, self-pollination offers significant advantages. It ensures reproductive success even when pollinators are scarce or absent. It also requires less energy, as the plant does not need to produce large amounts of pollen, nectar, or showy petals. This strategy is highly effective for preserving well-adapted parental traits in a stable environment.
8. How is the principle of cross-pollination applied in agriculture for crop improvement?
Cross-pollination is fundamental to artificial hybridisation in agriculture. Plant breeders intentionally cross-pollinate two different plant varieties with desirable traits (e.g., high yield and disease resistance). This is done by removing the anthers (emasculation) from one parent and manually dusting its stigma with pollen from the other parent. The resulting hybrid offspring often exhibit superior qualities, a phenomenon known as hybrid vigour.
9. Can a plant perform both self and cross-pollination?
Yes, some plants are capable of both. For example, in plants like Commelina, some flowers are chasmogamous (open, allowing for cross-pollination), while others are cleistogamous (remain closed, ensuring self-pollination). This dual strategy increases the chances of successful reproduction under varying environmental conditions, acting as a reproductive 'insurance policy'.
