What is self-incompatibility? Why does self-pollination not lead to seed formation in self-incompatible species?
Solution and Explanation
Self-incompatibility is a genetic mechanism in angiosperms that prevents self-pollination. It develop genetic incompatibility between individuals of the same species or between individuals of different species. The plants which exhibit this phenomenon have the ability to prevent germination of pollen grains and thus, prevent the growth of the pollen tube on the stigma of the flower. This prevents the fusion of the gametes along with the development of the embryo. As a result, no seed formation take place.
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 thin pencil of length \( f/4 \) is placed coinciding with the principal axis of a mirror of focal length \( f \). The image of the pencil is real and enlarged, just touches the pencil. Calculate the magnification produced by the mirror.
- CBSE CLASS XII - 2025
- electrostatic potential and capacitance
- A proton moving with velocity \( V \) in a non-uniform magnetic field traces a path as shown in the figure. The path followed by the proton is always in the plane of the paper. What is the direction of the magnetic field in the region near points P, Q, and R? What can you say about relative magnitude of magnetic fields at these points?
- CBSE CLASS XII - 2025
- Motion of charged particles in a magnetic field
- Assertion (A): In a first order reaction, if the concentration of the reactant is doubled, its half-life is also doubled.
Reason (R): The half-life of a reaction does not depend upon the initial concentration of the reactant in a first order reaction.- CBSE CLASS XII - 2025
- Chemical Kinetics
Rishika and Shivika were partners in a firm sharing profits and losses in the ratio of 3 : 2. Their Balance Sheet as at 31st March, 2024 stood as follows:
Balance Sheet of Rishika and Shivika as at 31st March, 2024Liabilities Amount (₹) Assets Amount (₹) Capitals: Equipment 45,00,000 Rishika – ₹30,00,000
Shivika – ₹20,00,00050,00,000 Investments 5,00,000 Shivika’s Husband’s Loan 5,00,000 Debtors 35,00,000 Creditors 40,00,000 Stock 8,00,000 Cash at Bank 2,00,000 Total 95,00,000 Total 95,00,000 The firm was dissolved on the above date and the following transactions took place:
(i) Equipements were given to creditors in full settlement of their account.
(ii) Investments were sold at a profit of 20% on its book value.
(iii) Full amount was collected from debtors.
(iv) Stock was taken over by Rishika at 50% discount.
(v) Actual expenses of realisation amounted to ₹ 2,00,000 which were paid by the firm. Prepare Realisation Account.- CBSE CLASS XII - 2025
- Dissolution of Partnership Firm
- Your school is organizing an Inter-House Science Model-Making Competition. As President of the Science Club, draft a notice to inform all House members from IX – XII about the competition and specify the number of registrations invited per house. Include other necessary details. You are Mitali/Mukesh. Put your notice in a box.
- CBSE CLASS XII - 2025
- Letter Writing
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