Outbreeding Devices and Artificial Hybridization: NEET Biology Notes
Welcome to Grip the Biology , your premier destination for high-quality, NCERT-aligned medical entrance preparation. We take pride in delivering content that doesn't just mirror textbooks but decodes them. This guide on Sexual Reproduction of Flowering plants is meticulously crafted to meet the rigorous standards of the NTA NEET-UG syllabus, focusing exclusively on the core concepts that matter most."
Before exploring the Reproductive details of the Outbreeding Devices and Artificial Hybridization: NEET Biology Notes ensure you have reviewed our previous guide on NEET Biology: Types and Agents of Pollination (Chasmogamous vs Cleistogamous Flowers) | Ultimate NCERT Guide to understand the reproductive context of flowering plants (Angiosperms) in the NEET journey."
Table of Contents
- Introduction: Why Plants Avoid Self-Pollination?
- What is Inbreeding Depression?
- Outbreeding Devices: Nature’s Anti-Selfing Mechanisms
- Dichogamy (Timing Mismatch)
- Herkogamy (Spatial Separation)
- Self-Incompatibility (The Genetic Barrier)
- Dicliny / Production of Unisexual Flowers
- Artificial Hybridization: Crop Improvement Technique
- Step-by-Step Process of Artificial Hybridization
- Emasculation (Removal of Anthers)
- Bagging (Protection from Unwanted Pollen)
- Dusting & Re-bagging
- High-Yield NEET MCQs with Detailed Solution
Introduction: Why Plants Avoid Self-Pollination?
- Self-pollination or Autogamy is transfer of pollen grains from anther to stigma of the same flower or another flower on the same plant.
Reasons to Plants Avoid Self-Pollination:
- Self pollination reduces Genetic Variation because Continuous self-pollination leads to breeding of similar alleles. As a result, Offspring have very less variation that lead to slow evolution and off spring have poor adaptability to changing environment.
- Self pollination Causes Inbreeding Depression because repeated self-pollination increases homozygosity. As a result ,harmful recessive alleles get expressed. This reduces fertility, seed viability, and vigour of plants. This is called inbreeding depression.
- Cross-pollination produces new gene combinations → new characters like disease resistance, drought tolerance. Self-pollination does not give this advantage.
💡 KNOW IT ALSO.
📝Hybrid vigour, or heterosis, is the opposite of inbreeding depression. Hybrid vigour makes plants strong in terms of growth, reproduction, yield, etc., whereas inbreeding depression makes plants weak in the above characteristics.".
What is Inbreeding Depression?
- The reduction in biological fitness and vigour of offspring due to continuous self-breeding or breeding between close relatives is called Inbreeding Depression.
- Inbreeding depression was first reported by Lund (1949) in Dianthus.
NEET Booster ! Dianthus exhibit Free Central placentation along with Primrose . To know about Aestivation and placentation, read comprehensive guide on Structure of Flower : Aestivation & Placentation | NEET Biology Guide
How does inbreeding depression occur ?
- All organisms carry some harmful recessive alleles, but they don’t express in heterozygous condition.
- Continuous self-pollination increases homozygosity and it makes recessive alleles become homozygous to get expressed . This makes the plant weaker.
Inbreeding Depression vs Hybrid Vigour - NEET Biology
| Feature | Inbreeding Depression | Hybrid Vigour / Heterosis |
|---|---|---|
| Cause | Continued self-pollination | Cross-pollination between unrelated plants |
| Genetic Condition | Homozygosity increases | Heterozygosity increases |
| Recessive Alleles | Harmful alleles get expressed | Harmful alleles remain hidden |
| Vigour | Loss of vigour | Gain of vigour |
| Fertility & Yield | Decreases | Increases |
| Disease Resistance | Decreases | Increases |
| Example | Maize after 4-5 generations of selfing | Hybrid maize, Hybrid rice |
| NEET Line | "Continued self-pollination causes inbreeding depression" | "Cross-pollination leads to hybrid vigour" |
Outbreeding Devices: Nature’s Anti-Selfing Mechanisms
- In Flowering plants, Continued self pollination result inbreeding depressions.
- Therefore flowering plant has developed many devices to prevent self pollination and to encourage the cross pollination because cross pollination lead the genetic variability and it is an essential elements for the process of evolution.
- There are various devices that are given by the nature to the flowering plants to encourage the cross pollination. These devices are called as outbreeding devices.
- The maturation of the anther and the stigma in a flower is not synchronised ( not same time ?
- This means that the time of stigma receptivity and the time of pollen release are different. This condition is called dichogamy.
💡 Protogyny and Protandry
📝When the stigma become receptive before the release of pollen. This condition is called protogyny. Example : Magnolia, Aristolochia.
📝When the pollen are release before the stigma became receptive. this condition is called Protandry. Example : Salvia, Helianthus.
Herkogamy (Spatial Separation)
- In some bisexual flowers, the anther and style are arranged in such a way that self-pollination is not possible. The anther and stigma are located at different positions, so the pollen cannot come in contact with the stigma. This condition is called herkogamy.
💡 Herkogamy
📝 In caryophyllaceae, the style is much longer than stamen so the pollen is fail to reach the stigma.
📝 Similarly in Gloriosa, the anther release pollen at much distance from stigma. So there is no contact between pollen and stigma.
- It is important to note that herkogamy prevents autogamy but does not prevent geitonogamy. This means pollen from another flower of the same plant can still land on the stigma.
💡Related study to understand about the Microsporogenesis, Pollen Grain Structure, and Pollen Allergy | NEET Biology
Self incompatibility -
- Self-incompatibility is a genetic mechanism which prevents self-pollen from fertilizing the ovules by inhibiting pollen germination or pollen tube growth in the pistil. For Example : Tobacco, Potato, Petunia, Brassica, Raphanus
- The Significance of self-incompatibility are - It prevents both autogamy and geitonogamy. It promotes cross-pollination and outbreeding. It prevents inbreeding depression and promotes hybrid vigour
Dicliny / Production of Unisexual Flower
- The production of unisexual flowers is a device to prevent self-pollination and is called dicliny or unisexuality. Dicliny is of two types:
- Monoecious plants: Male and female flowers are present on the same plant. This prevents autogamy but not geitonogamy. Examples: Maize, Castor.
- Dioecious plants: Male and female flowers are present on different plants. This prevents both autogamy and geitonogamy. Therefore, there is no chance of self-pollination. Example: Papaya.
| Device | Barrier | Type | Prevents Autogamy | Prevents Geitonogamy |
|---|---|---|---|---|
| Dichogamy | Time barrier | Physiological | ✅ Yes | ✅ Yes |
| Herkogamy | Physical barrier | Morphological | ✅ Yes | ❌ No |
| Self-incompatibility | Genetic barrier | Genetic | ✅ Yes | ✅ Yes |
| Dicliny – Monoecious | Unisexual flowers on same plant | Morphological | ✅ Yes | ❌ No |
| Dicliny – Dioecious | Unisexual flowers on different plants | Morphological | ✅ Yes | ✅ Yes |
Note: Dioecy is the dioecious condition of Dicliny. NCERT uses the term "Unisexuality" instead of "Dicliny".
Artificial Hybridization: Crop Improvement Technique
- Artificial Hybridization is one of the major approaches of crop improvement programmes.
- The main objective is to cross different varieties or species to combine desirable characters (like high yield, disease resistance) into a single superior plant.
- Core Rule: In this process, it is critical to ensure that only the desired pollen grains are used for pollination and the stigma is protected from unwanted contamination.
- Artificial Hybridisation is one of the approach to get superior breed under plant breeding programme.
💡Related study to understand about the Female Reproductive System in Plants: Structure of Ovule & Megasporogenesis | NEET Biology
Step-by-Step Process of Artificial Hybridization
Emasculation (Removal of Anthers)
- The removal of anthers from the flower bud of a female parent before they dehisce (mature/burst open) using a pair of forceps is called Emasculation
- The purpose of Emasculation is to prevent self-pollination within the same flower.
☑️ Important NEET Note:
📝 This step is required only if the female parent bears bisexual flowers.
Bagging (Protection from Unwanted Pollen)
- The Covering of emasculated flower with a bag of suitable size (usually made of butter paper) is called Bagging .
- The purpose of bagging is to prevent contamination of its stigma with unwanted pollen grains floating in the air.
Dusting (Artificial Pollination)
- When the stigma of the bagged flower attains receptivity (becomes mature), mature pollen grains collected from the anthers of the selected male parent are carefully dusted onto the stigma.
Re-bagging
- Immediately after dusting the desired pollen, the flower is covered with the bag again.
- The purpose of Re-bagging is to protect the developed stigma until the fruits and seeds are fully formed and harvested.
💡 Special NEET Booster Note (Crucial for Exams)
- If the female parent produces unisexual flowers (like Papaya), Emasculation is NOT needed.
- In this case, the female flower buds are directly bagged before they open. When the flower opens and the stigma becomes receptive, pollination is carried out using the desired pollen, and the flower is re-bagged.
MULTIPLE CHOICE QUESTIONS
🔥 100% CHALLENGE
"Questions yahi se aayega... taiyari jeet ki!"
1. Inbreeding depression is caused by the continuous
A. Cross pollination
B. Self pollination
C. Double fertilisation
D. Triple fusion
Answer : B
2. Nature developed outbreeding devices to promote :
A. Cross pollination
B. Self pollination
C. Genetic variation
D. All of the above
Answer: A
3. Consider the following devices that can prevent autogamy and select the correct code:
1. There is no synchronization between pollen release and stigma receptivity.
2. In some plant species, pollens are released before the stigma receptive or stigma become receptive much before than pollen release.
3. In some plant species, anther and stigma are located at different position so that pollen can not make contact with stigma.
A. Only 2 B.Only 1
C. Both 1 and 2
D. 1, 2 and 3
Answer : D
4. Self incompatibility is a genetic mechanism to prevent self pollination. Self incompatibility refer to:
A. Preventing of germination or growth of pollen tube from the fertilizing the ovule.
B. There is no synchronization between pollen release and stigma receptivity.
C. Location of Anther and stigma are at different position.
D. Production of unisexual flower in plants.
Answer : A
5. In which of the plants , male flower and female flower are produced.
A. Papaya and Maize
B. Papaya and Castor
C. Maize and Castor
D. Papaya, Maize and Castor
Answer: C
6. Production of unisexual flower i.e male and female flower are different in same plant, prevent
A. Xenogamy but not autogamy.
B. Geitonogamy but not autogamy.
C. Xenogamy only
D. Autogamy but not geitonogamy.
Answer : D
7. Consider the following statement and select the correct code:
1. Papaya is diocious because male and female flowers are present on different plants.
2. Dioecy condition prevent both autogamy and geitonogamy.
A. Only 1 B. Only 2
C. Both 1 and 2
D. Neither 1 nor 2
Answer : C
8. Which one of the following is/ are approach in Crop improvement programme.
A. Artificial Hybridisation
B. Emasculation
C. Bagging
D. All of the above
Answer : D
9. Consider the following statement and select the option corresponding to correct statements:
1. Non emascusled flower is covered by suitable size of bag made up of butter paper.
2. After dusting of desired pollen grain, there is no need of rebagging.
3. In Unisexual flower, Emasculation is essential.
4. In Crop improvement programme, stigma is protected from unwanted pollen grain.
A . One B . Two
C. Three D. Four
Answer: A
10. Consider the following statement and select the correct code
1. Removal of Anther from flower by using of forceps called emasculation.
2. Emasculated flower is covered by suitable size of bag made up of butter paper. This is called bagging.
3. After dusting of desired pollen grain, the stigma is rebagged.
A. 1 and 2 B. 1 and 3
C. 2 and 3 D. 1, 2 and 3
Answer : D
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