What is triple fusion? Where and how it take place? Name the nuclei involved in triple fusion.
Solution and Explanation
Triple fusion is the fusion of the male gamete with two polar nuclei inside the embryo sac of the angiosperm.
This process of fusion takes place inside the embryo sac. When pollen grains fall on the stigma, they germinate and give rise to the pollen tube that passes through the style and enters into the ovule.After this, the pollen tube enters one of the synergids and releases two male gametes there. Out of the two male gametes, one gamete fuses with the nucleus of the egg cell and forms the zygote(syngamy). The other male gametes fuses with the two polar nuclei present in the central cell to form a triploid primary endosperm nucleus.
Since this process involves the fusion of three haploid nuclei, It is known as triple fusion. It results in the formation of the endosperm. One male gamete nucleus and two polar nuclei are involved in this process.
Top Questions on sexual reproduction in flowering plants
The following question is based on pollination. Study the figures carefully and answer the questions that follow.
- Give the scientific terms for the processes taking place in Figures A and B respectively.
- Mention two conditions necessary for the process occurring in Figure B.
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- [(i)] State one advantage and one disadvantage of the process occurring in Figure B.
OR - [(ii)] Name one plant where, in some flowers only, the process in Figure B takes place and give the reason responsible for it.
- [(i)] State one advantage and one disadvantage of the process occurring in Figure B.
- CBSE CLASS XII - 2025
- Biology
- sexual reproduction in flowering plants
- Student to attempt either option (A) or (B): (A) What is meant by ‘right’ and ‘wrong’ type of pollen when pollen lands on the stigma? A two-celled right type pollen has landed on the stigma. Explain the events taking place till fertilization in angiosperms. Why is pollen pistil interaction said to be dynamic?
OR
(B)- Give the schematic representation of oogenesis in human females indicating chromosome number at each step.
- In which part of the female reproductive system do the following events take place?
- I. Formation of corpus luteum
- II. Maturation of tertiary follicle
- III. Fertilisation
- IV. Implantation
- CBSE CLASS XII - 2025
- Biology
- sexual reproduction in flowering plants
- Choose the option that correctly describes the gynoecium of Michelia:
- CBSE CLASS XII - 2025
- Biology
- sexual reproduction in flowering plants
- Given below are the events that are observed in an artificial hybridisation programme. Arrange them in the correct sequential order and select the correct option.
- Re-bagging
- Selection of parents
- Bagging
- Dusting the pollens on stigma
- Emasculation
- Collection of pollens from male parent
- CBSE CLASS XII - 2025
- Biology
- sexual reproduction in flowering plants
- Select the following statements that are true for insect pollinated flowers from the given options.
- Majority of these flowers are large, colourful and rich in nectar.
- Nectars and seeds are usual floral rewards to attract insects for pollination.
- Pollen grains of these flowers are generally mucilaginous so as to stick to the body of the insects.
- A foul odour is emitted by some flowers to attract flies and beetles.
- CBSE CLASS XII - 2025
- Biology
- sexual reproduction in flowering plants
Questions Asked in CBSE CLASS XII exam
A ladder of fixed length \( h \) is to be placed along the wall such that it is free to move along the height of the wall.
Based upon the above information, answer the following questions:(iii) (b) If the foot of the ladder, whose length is 5 m, is being pulled towards the wall such that the rate of decrease of distance \( y \) is \( 2 \, \text{m/s} \), then at what rate is the height on the wall \( x \) increasing when the foot of the ladder is 3 m away from the wall?
- CBSE CLASS XII - 2025
- Application of derivatives
- A meeting will be held only if all three members A, B and C are present. The probability that member A does not turn up is 0.10, member B does not turn up is 0.20 and member C does not turn up is 0.05. The probability of the meeting being cancelled is:
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- Probability
- Vishesh, Manik and Amit were partners in the ratio 5 : 4 : 1. Amit retired on 31st March, 2024. Vishesh and Manik decided to share Amit’s share in the ratio 2 : 3. What will be the new profit sharing ratio between Vishesh and Manik?
- CBSE CLASS XII - 2025
- Retirement and Death of a Partner
- The electric field in a region is given by \( \vec{E} = 40x \hat{i} \, \text{N/C}. \) Find the amount of work done in taking a unit positive charge from a point (0, 3m) to the point (5m, 0).
- CBSE CLASS XII - 2025
- Electrostatics
- Consider the Linear Programming Problem, where the objective function \[ Z = x + 4y \] needs to be minimized subject to the following constraints: \[ 2x + y \geq 1000, \] \[ x + 2y \geq 800, \] \[ x \geq 0, \quad y \geq 0. \] Draw a neat graph of the feasible region and find the minimum value of $Z$.
- CBSE CLASS XII - 2025
- Linear Programming Problem
Concepts Used:
Pollination and Double Fertilization
Pollination is defined as the pre-fertilization event or process, where pollen grains from another are transferred to the stigma of a flower.
Double fertilization is a complex process that involves the fusion of one female gametophyte with two male gametes.
Types of Pollination:
All plants having flowers completely rely on the pollination method for reproduction. There are 2 types of pollination –
- Self Pollination
- Cross-Pollination
The end products of double fertilization are:
- Diploid Zygote
- Primary Endosperm Nucleus