Question 1

Which of the following statements is not correct?

Accepted Answer

More the one pollen tube of same species can grow into the style. It is frequently found in nature.

Question 2

What is self-incompatibility? Why does self-pollination not lead to seed formation in self-incompatible species?

Accepted Answer

Self-incompatibility is a condition where pollen is not able to fertilize the same flower or other flowers on the same plant due to inhibition of the growth of the pollen tube in the stigma and style, thereby preventing delivery of male gametes to the ovules. The absence of fusion of male and female gamete leads to no seed formation in these plants.

Question 3

Self-incompatibility is a device forI. Ensuring cross-pollinationII. Preventing self-pollinationIII. Ensuring self-fertilisationIV. Genetic control for self-fertilisationChoose the correct statements from those given above

Accepted Answer

I, II, III and IV are correctFlowering plants have developed many devices to discourage self-pollination. In some species, pollen, releases and stigma receptibility is non-syncronised, i.e., either the pollen is released before the stigma becomes receptive or stigma becomes receptive much before the release of pollen.In some other species the anther and stigma are placed at the different positions so that the pollen can not come in contact with the stigma of same flower. Both these devices prevent autogamy.The third device to prevent inbreeding is self-incompatibility. This is genetic a mechanism and prevents self pollination (from same flower or other flower of same plant) from fertilizing the ovules by inhibiting pollen germination or pollen tube growth in pistil.

Question 4

The condition of maturation of stigma before anthers of the same flower is

Accepted Answer

The phenomenon depicting maturation of female part of a flower earlier than the male part of the flower is known as protogyny.

Question 5

Intra-species incompatibility can be overcome by

Accepted Answer

A suspension containing pollen grains is injected into the ovum. This is called as intra - ovarian pollination. The buds from flower are emasculated when it is in the bud phase. This is done previous to the dehiscence of the anthers and the pollen are collected under aseptic conditions. The pollen are then introduced into the ovum using a syringe resulting in pollination.

Question 6

Self-incompatibility is a device forI. Ensuring cross-pollinationII. Preventing self-pollinationIII. Ensuring self-fertilisationIV. Genetic control for self-fertilisationChoose the correct statements from those given above

Accepted Answer

I, II, III and IV are correctFlowering plants have developed many devices to discourage self-pollination. In some species, pollen, releases and stigma receptibility is non-syncronised, i.e., either the pollen is released before the stigma becomes receptive or stigma becomes receptive much before the release of pollen.In some other species the anther and stigma are placed at the different positions so that the pollen can not come in contact with the stigma of same flower. Both these devices prevent autogamy.The third device to prevent inbreeding is self-incompatibility. This is genetic a mechanism and prevents self pollination (from same flower or other flower of same plant) from fertilizing the ovules by inhibiting pollen germination or pollen tube growth in pistil.

Question 7

The condition of maturation of stigma before anthers of the same flower is

Accepted Answer

The phenomenon depicting maturation of female part of a flower earlier than the male part of the flower is known as protogyny.

Question 8

Intra-species incompatibility can be overcome by

Accepted Answer

A suspension containing pollen grains is injected into the ovum. This is called as intra - ovarian pollination. The buds from flower are emasculated when it is in the bud phase. This is done previous to the dehiscence of the anthers and the pollen are collected under aseptic conditions. The pollen are then introduced into the ovum using a syringe resulting in pollination.

Question 9

Self-incompatibility is a process toI.	ensure cross-pollinationII.	prevent self-fertilisationIII.	ensure self-fertilisationIV.	genetic control for self-fertilisationChoose the correct process for given statements.

Accepted Answer

I, II and IV processes are correct for given statement.Self-incompatibility is a genetic mechanism, i.e. genetic control for self-fertilisation by preventing self-pollination, i.e. from the same flower or other flower of the same plant from fertilising the ovules by inhibiting pollen germination or pollen tube growth in the pistil. It ensures cross-pollination.Thus, option (d) is correct.

Question 10

"Incompatibility is a natural barrier in the fusion of gametes". Justify the statement.

Accepted Answer

• Incompatibility is considered the most widespread and effective device to prevent inbreeding and outbreeding.•Pollen pistil interaction is a dynamic process involving pollen recognition followed by promotion or inhibition of the pollen.•It acts as a natural barrier by the interaction of chemical substances produced by the style.•Normally the pollen belonging to the right mating type germinates on stigma, develop a pollen tube and bring about fertilization.•The pollen grains belonging to other mating types are discarded.

Question 11

Does self-incompatibility impose any restrictions on autogamy? Give reasons and suggest the method of pollination in such plants.

Accepted Answer

Self-incompatibility imposes restrictions on autogamy. The season far this may be as Majority of flowering plants produce hermaphrodite flowers and when pollens grains comes in contact with the stigma of the same flower to continue self-pollination.Such type of continued self-pollination result in inbreeding depression. That’s why flowering plants have developed many devices to discourage self-pollination and to encourage cross-pollination. One of the major way to prevent self-pollination is self-sterility.Self-sterility in some bisexual flowers, if the pollen grains fall on the stigma of the same flower, germination does not occur. But the same pollen grains germinate when they fall on the stigma of other flowers of the same species. It is a genetic mechanism to prevent self pollination.

Question 12

Majority of flowering plants-

Accepted Answer

Majority of flowering plants produce hermaphrodite flowers and pollen grains are likely to come in contact with the stigma of the same flower.

Question 13

Self-incompatibility -I. Is a device to prevent inbreeding.II. Provides a biochemical block to self-fertilization.III. Ensures cross-fertilization.IV. Is governed by pollen-pistil interactionV. Is governed by series of multiple alleles.VI. Prevents self pollen (from the same flower or other flowers of the same plant) from fertilizing the ovules by inhibiting pollen germination or pollen tube growth in the pistil.

Accepted Answer

Self-incompatibility refers to the inability of a plant with functional pollen to set seeds when self pollinated. It is the failure of pollen from a flower to fertilize the same flower or other flowers of the same plant.

Question 14

Self-incompatibility -

Accepted Answer

Self-incompatibility is a general name for several genetic mechanisms that prevent self-fertilization in sexually reproducing organisms, and thus encourage outcrossing and allogamy which maintains variation.

Question 15

A plant that is self-incompatible has a genotype of S5​Sq for S-locus. It recieves pollen from a plant that is S3​Sq. Which of the following is most likely to occur?

Accepted Answer

This process is called as self-incompatibility, here if the pollen grain and the female plant has the same genotype then the pollen will not germinate. They will only germinate if the pollen grains and female plant have different. In this case a plant has a genotype of ﻿﻿S5​Sq for S-locus. It receives pollen from a plant that is S3​Sq so only about half of the pollen will germinate.

Question 16

The above diagram refers the self-inompatibility. The genotypes of embryo and endosperms are –

Accepted Answer

The embryo is produced by the fertilization of the male and female gametes. However, the embryo is protected by the endosperm in most of the seed. The endosperm is usually triploid in nature. The embryo consists of a large number of nutrients that are to be supplied to the endosperm that helps in its development.

Question 17

Considering the genetic basis of self-incompatibility which of the following options is correct. Male plant is S1​,S3​ and female plant is S1​,S2​.

Accepted Answer

Self-incompatibility is a widespread mechanism in flowering plants that prevents inbreeding and promotes outcrossing. It is done by inhibiting the growth of the pollen tube from its own species. Since S1​ and S2​ is the self genetic composition, pollen of such arrangement will be inhibited to develop a pollen tube. Hence pollen S3​ develops a pollen tube.

Question 18

Autogamy can occur in a chasmogamous flower if:(A) Pollen matures before maturity of uvule(B) Ovules mature before maturity of pollen(C) Both pollen and ovules mature simultaneously(D) Both anther and stigma are of equal lengths

Accepted Answer

(C) Autogamy is a method of self-pollination. It is a process in which the stigma of a flower receives pollens from the anther of same flower. For autogamy both the sex organs of a chasmogamous flower should mature at the same time. As chasmogamous flowers open at maturity, pollen release and stigma receptivity should be synchronised for the process of autogamy. In such flowers, the length of anther and stigma plays secondary role in autogamy, e.g., in case of protandry (in which pollens mature early) and protogyny (in which stigma matures early) leads to cross-pollination.

Question 19

Does self-incompatibility impose any restrictions on autogamy? Give reasons and suggest the method of pollination in such plants.

Accepted Answer

Self-incompatibility is the condition in which pollen from the same plant cannot pollinate the flower. Thus, self-incompatibility imposes complete restriction on autogamy. This evolution might have occurred in order to prevent too much inbreeding because continuous inbreeding prevent variations. In such plants, cross pollination is the norm and pollen from a plant pollinates the flower on another plant. This ensures accumulation of gene pools from two different plants.

Question 20

Which of the following statement(s) is/are correct about self-incompatibility ?(i) It is a device to prevent inbreeding.(ii) It provides a biochemical block to self-fertilization.(iii) It ensures cross-fertilization.(iv) It is governed by pollen-pistil interaction.(v) It is governed by series of multiple alleles.(vi) It prevents self-pollen (from the same flower of other flowers of the same plant) from fertilizing the ovules by inhibiting pollen germination of pollen tube growth in the pistil.

Accepted Answer

All the statements are correct about self -incompatibility. Self-incompatibility is a general name for several genetic mechanisms in angiosperms, which prevent self-fertilization and thus encourage outcrossing and allogamy. In plants with self -incompatibility, when a pollen grain produced in a plant reaches a stigma of the same plant or another plant with a similar genotype, the process of pollen germination, pollen tube growth, ovule fertilization, and embryo development is halted at one of its stages, and consequently no seeds are produced.

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