Q.Emasculation and bagging are the two important steps carried during artificial hybridisation to obtain superior varieties of desired plants. Explain giving reasons, in which types of flowers and at what stages are the two processes carried out.
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🔒 Start your 14-day free trial to unlock the full solution →Part (a)Concept understanding — Bagging Technique Utility
Let’s begin with something you already know from everyday life.
Imagine you have to make a very important decision — say, which college course to pick. You could ask one friend for advice. But that one friend might be biased (they love their own subject) or misinformed (they heard something wrong). So instead, you ask ten different people — teachers, seniors, parents, counsellors — and then take a majority vote or an average of their opinions. That collective decision is almost always more reliable than any single person’s advice.
That is the core intuition behind Bagging.
What Bagging Does
In data analysis and machine learning, Bagging stands for Bootstrap Aggregating. It is a technique used to make a prediction model more stable and accurate.
Here is the precise meaning: instead of building one single model (like one decision tree or one rule-based classifier) on the entire dataset, you create many slightly different versions of the same model, each trained on a different random sample of the original data. Then you combine all their outputs — usually by taking a majority vote (for classification) or an average (for prediction).
The key word is Bootstrap. A bootstrap sample is created by randomly picking data points from the original dataset with replacement — meaning the same data point can be picked more than once in a single sample, and some points may be left out. Each sample is different, so each model sees a slightly different view of the world.
Why It Matters
The main utility of Bagging is reducing variance — that is, reducing the model’s tendency to change wildly if you give it a slightly different set of data.
Think of it this way: a single model can be “nervous” — it might overreact to a few unusual data points (outliers) or to random noise in the data. But when you average the opinions of many such models, their individual nervousness cancels out. The combined model becomes calm, stable, and more accurate.
Bagging works best when the individual models are unstable — meaning they change a lot with small changes in the training data. Decision trees are a classic example. Bagging turns a shaky tree into a robust forest.
Key Points to Remember (for exams)
- Purpose: To improve accuracy and stability by combining multiple models.
- How it works: Create many random samples (with replacement) from the original data. Train a separate model on each sample. Combine their predictions.
- Why it helps: Reduces overfitting (the model memorising noise) and lowers variance.
- Trade-off: It does not reduce bias much — if the individual model is fundamentally weak, bagging won’t fix that. It only makes a good model more reliable. …
Part (b)Concept understanding — Parthenocarpy Induction Mechanism
Let’s start with something you already know: a fruit is the ripened ovary of a flower. Normally, for that ovary to swell into a fruit, the flower must first be pollinated — pollen lands on the stigma, a pollen tube grows down, and fertilisation happens. Seeds then develop inside the fruit. That’s the usual sequence.
Now imagine a fruit that forms without any of that. No pollination, no fertilisation, no seeds. That’s parthenocarpy — from Greek parthenos (virgin) and karpos (fruit). The fruit develops from the ovary all by itself, as if it skipped the entire reproductive step.
How is that induced? In nature, some plants do it spontaneously — bananas, grapes, oranges, cucumbers. But commercially, farmers and horticulturists often induce parthenocarpy artificially. The mechanism is simple in principle: you trick the ovary into thinking it has been pollinated and fertilised.
The key is a group of plant hormones called auxins and gibberellins. When pollen lands on a stigma, it triggers a surge of these hormones in the ovary, which makes it grow. If you spray the flower with synthetic auxins (like 2,4-D or NAA) or gibberellins (like GA₃) at the right time, the ovary gets the same chemical signal — and starts swelling into a fruit, even though no fertilisation occurred.
This is not genetic modification. It’s a hormonal treatment applied externally. The plant itself is not altered permanently; only that particular flower’s development is redirected.
Why does this matter? Two big reasons:
- Seedless fruits — consumers prefer seedless watermelons, grapes, cucumbers. Parthenocarpy gives you that without any seeds to remove.
- Reliable yield — if weather or lack of pollinators prevents pollination, the crop can still set fruit. This is especially useful in greenhouses or during rainy seasons when bees are inactive.
What NCERT says: In the Class 12 Biology textbook (Chapter 2, Sexual Reproduction in Flowering Plants), parthenocarpy is defined as the development of fruit without fertilisation. The textbook mentions that it can be induced by applying growth hormones like auxins, and that such fruits are seedless. Examples given: banana, grapes, cucumber. …
Part (a)
- Emasculation = removal of the anthers (stamens) from a flower bud before the anthers dehisce. It is done only in bisexual flowers (which have both stamens and pistil) so that the flower cannot self-pollinate; it must be carried out at the bud stage, before the anthers mature and shed pollen. Unisexual female flowers need no emasculation.
- Bagging = covering the emasculated flower (or an unopened female flower) with a butter-paper/plastic bag. It is done immediately after emasculation, in both bisexual (emasculated) and unisexual female flowers, to prevent contamination of the stigma by unwanted foreign pollen until it becomes receptive; the desired pollen is then dusted on and the flower re-bagged. …
Part (a): Emasculation (removing anthers from a bud of a bisexual flower before pollen is shed) prevents self-pollination, and bagging (covering the flower right after emasculation) prevents unwanted cross-pollination — both ensure a controlled cross in artificial hybridisation. Part (b): Apomixis is the production of seeds without fertilisation; it gives clonal, true-breeding seeds that can fix hybrid vigour and be replanted year after year.
Part (a)
In artificial hybridisation, a breeder crosses two selected parents to combine desirable traits. To be sure the female parent is fertilised only by the chosen pollen, two steps are essential.
Emasculation is the removal of the anthers from a flower before they dehisce. It is performed only on bisexual flowers, because such flowers contain functional stamens that could otherwise self-pollinate the same flower. It must be done at the bud stage, i.e. before the anthers mature and shed pollen; opening the bud, the anthers are picked out with forceps. In unisexual female flowers (e.g. maize cobs) there are no anthers, so emasculation is not needed. …
- CBSE 2026Set ANNUAL1 markMCQQ.An example of a parthenocarpic fruit is(a) Banana(b) Apple(c) Strawberry(d) Walnut
›Reveal solutionSolution
Parthenocarpy is the development of fruit without fertilisation, giving seedless fruits; banana is the classic example.
Fertilisation normally triggers the ovary to develop into a fruit and the ovules into seeds. In parthenocarpic fruits, the ovary develops into a fruit WITHOUT fertilisation occurring, so the fruit is seedless. Commercially important parthenocarpic fruits include banana (and it can be indu …
- CBSE 2025Set ANNUAL1 markMCQQ.Assertion (A) : No seeds formation found in the Parthenocarpy fruits. Reason (R) : Such type of fruits are formed without fertilization of the ovary.(a) Both (A) and (R) are correct and (R) is the correct explanation of (A).(b) Both (A) and (R) are correct but (R) is not the correct explanation of (A).(c) (A) is correct but (R) is incorrect.(d) Both (A) and (R) are incorrect.
›Reveal solutionSolution
Parthenocarpic fruits are seedless precisely because they develop without fertilisation of the ovary.
Assertion (A) is correct: parthenocarpic fruits (e.g. seedless banana, and seedless grapes or watermelon obtained by auxin treatment of the ovary) do not contain seeds. Reason (R) is also correct and directly explains why: parthenocarpy is the development of a fruit from the ovary without fertilisation taking place. Since fertilisation (fusion of male and female gametes) is what norm …
- CBSE 2024Set ANNUAL1 markMCQQ.Development of fruit without fertilization is called(a) polyembryony(b) parthenocarpy(c) parthenogenesis(d) apomixis
›Reveal solutionSolution
Parthenocarpy is the formation of a fruit without fertilization, typically producing seedless fruit.
Parthenocarpy is defined as the development of a fruit from the ovary without the occurrence of fertilization, and such fruits are usually seedless (e.g., bananas, some grape varieties). It can occur naturally or can be induced artificially through application of growth hormones like auxins. Parthenogenesis (c) refers to development of an embryo from an unfertilized egg (seen in some animals), polyembryony (a) is the occurrence of more than one embryo in a single seed, and apomixis (d) i …
- CBSE 2024Set ANNUAL1 markMCQQ.The phenomenon wherein, the ovary develops into fruit without fertilization is called(a) Parthenocarpy(b) Apomixis(c) Embryogenesis(d) Syngamy
›Reveal solutionSolution
Parthenocarpy is the development of a fruit from the ovary without fertilization, giving seedless fruit.
Parthenocarpy refers to the development of the ovary into a fruit without the ovules being fertilized. Since fertilization does not occur, no seeds are formed, resulting in a seedless fruit — e.g., banana. Parthenocarpic fruit development can occur naturally or be artificially induced (e.g., by application of growth hormones). Apomixis is a different phenomenon, where seeds are produced without the fusion of gametes (asexual reproduction that mimics sexual re …
- CBSE 2022Set ANNUAL1 markQ.Banana is considered a good example of parthenocarpy. Give reason.
›Reveal solutionSolution
Banana fruit develops without fertilisation (parthenocarpy), giving the commercially valuable seedless fruit.
Parthenocarpy is the development of a fruit from the ovary without fertilisation having occurred, so the resulting fruit is typically seedless. It can occur naturally or be induced artificially by applying growth hormones such as auxins to unpollinated/unfertilised flowers.
…
- CBSE 2021Set OC_BOTANY1 markQ.Define parthenocarpy.
›Reveal solutionSolution
Parthenocarpy uncouples fruit development from fertilisation, so the ovary matures into a fruit even though no seeds are formed.
Definition and mechanism
Normally, fertilisation of the egg cell (and the resulting hormonal changes) triggers the ovary wall to develop into a fruit while the fertilised ovules develop into seeds. In parthenocarpy, the ovary develops into a fruit without fertilisation occurring, so the fruit lacks seeds. It can occur naturally in some species or can be induced artificially by applying growth hormones such as auxins to unpollinated flowers, which mimic the hormonal trigger normally provided by fertilisation.
Examples and significance
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- CBSE 2020Set HE8241 markQ.Fill in the blank: Which fruits develop without fertilisation are called ______.
›Reveal solutionSolution
Fruits that develop without fertilisation are called parthenocarpic fruits; the process is parthenocarpy.
Normally, after double fertilisation the ovary develops into the fruit and the ovules develop into seeds. In some plants, however, the ovary can swell and mature into a fruit even when fertilisation has NOT occurred. Such seedless fruits are called parthenocarpic fruits, and the phenomenon is called parthenocarpy.
…
- CBSE 2019Set ANNUAL1 markQ.What is Apomixis?
›Reveal solutionSolution
Apomixis = production of seeds without fertilisation — an asexual method that outwardly resembles sexual reproduction, giving clonal (parent-identical) seeds.
Concept
Normally a seed forms only after fertilisation of the egg. In apomixis, however, seeds are formed without fertilisation — for example, the diploid egg cell or another cell of the ovule develops directly into an embryo without meiosis and syngamy. The resulting seeds are genetically identical to the mother plant (clones).
Significance
- Seen in some Citrus, in the family Asteraceae, and in many grasses. …
- CBSE 2018Set ANNUAL1 markMCQQ.Fruits develop without fertilisation are called :(a)(i) False fruit(b)(ii) True fruit(c)(iii) Parthenocarpic fruit(d)(iv) Dry fruit
›Reveal solutionSolution
A fruit that develops from the ovary without fertilisation is a parthenocarpic fruit — option (iii). Such fruits are seedless.
Concept
Normally, after double fertilisation the ovule becomes the seed and the ovary matures into the fruit. Parthenocarpy is the development of the fruit from the ovary without fertilisation, so no true seed is formed. This can occur naturally or be induced by spraying growth hormones such as auxins and gibberellins.
Why the other options are wrong
- (i) False fruit — a fruit in which tissue other than the ovary (e.g. the thalamus in apple) contributes to the flesh; fertilisation has still occurred.
- (ii) True fruit — a fruit that develops from the ovary after normal fertilisation. …
- CBSE 2018Set ANNUAL1 markMCQQ.In which of the following species of plants seeds are produced through apomixis:(a) Asteraceae and Grass(b) Mustard(c) Citrus and Mango(d) None of these
›Reveal solutionSolution
Apomixis, a form of asexual reproduction that mimics seed formation without fertilisation, occurs in some Asteraceae and grasses.
Apomixis is the production of seeds without the fusion of gametes (no fertilisation). It is a form of asexual reproduction that mimics sexual seed formation. In NCERT, apomixis is described in several species of Asteraceae and in grasses, where the diploid egg cell forms without meiosis a …
- CBSE 2015Set ANNUAL1 markMCQQ.Multiple Choice Question: Development of fruit without fertilization and are seedless known as(a) Polyembryony(b) Apomixix(c) Parthenocarpy(d) Parthenogenesis
›Reveal solutionSolution
Fruit development in the complete absence of fertilisation, producing a seedless fruit, is called parthenocarpy.
Normally a fruit develops from the ovary only after fertilisation has occurred, and the fertilised ovules inside develop into seeds. In some plants, however, the ovary enlarges into a fruit without any fertilisation taking place — since no zygote or embryo forms, no seeds are produced, so the resulting fruit is seedless. This phenomenon is called parthenocarpy. It can occur naturally (e.g. banana, seedless grapes, some varieties of cucumber) or can be induced artificially by applying growth hormones such as auxins to the unpollinated pistil/stigma.
The other options describe different phenomena and are ruled out:
- Apomixis (b): seeds are formed without the fusion of gametes — an asexual mode of seed formation that mimics sexual reproduction (common in some grasses, Citrus, Asteraceae). It still produces seeds, unlike parthenocarpy. …
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