31 Years NEET Previous Year Questions: Sexual Reproduction in Flowering Plants - 1 - NEET MCQ

To determine the correct set of statements, we need to analyze each statement individually based on the characteristics of water-pollinated plants and specific examples given:

Statement A: "The flowers of Vallisneria are colourful and produce nectar."
This statement is incorrect. Vallisneria is an example of a water-pollinated (hydrophilous) plant. Unlike insect-pollinated flowers, which are often colorful and produce nectar to attract pollinators, water-pollinated flowers typically lack bright colors and nectar because they do not need to attract insects or other animals. Vallisneria flowers are small and inconspicuous.

Statement B: "The flowers of water lily are not pollinated by water."
This statement is correct. Water lilies are typically pollinated by insects, not by water. The large and colorful flowers of water lilies are adapted to attract insect pollinators, contrasting starkly with the typical features of water-pollinated flowers.

Statement C: "In most of water-pollinated species, the pollen grains are protected from wetting."
This statement is correct. In water-pollinated plants, the pollen grains often have a covering or are structured in a way that prevents them from becoming waterlogged and sinking. This adaptation allows them to float on the water's surface and reach the female parts of other plants.

Statement D: "Pollen grains of some hydrophytes are long and ribbon like."
This statement is correct. In some water-pollinated plants, such as seagrasses (e.g., Zostera), the pollen grains are indeed elongated and ribbon-like, which helps them to be transported more effectively by water currents.

Statement E: "In some hydrophytes, the pollen grains are carried passively inside water."
This statement is also correct. Many hydrophytes have pollen grains that are transported by water currents, rather than being actively carried by animal pollinators or the wind. This passive transport is typical in water-pollinated species.

Based on the analysis, Statements B, C, D, and E are correct, while Statement A is incorrect.
Therefore, the correct answer is: Option D: B, C, D, and E only

The given diagram shows a wind pollinated plant showing compact inflorescence and well exposed stamens.
Stamens are exposed so complete autogamy does not occur.

Large, colorful, fragrant flowers with nectar are features that attract biotic pollinators. Insect pollinated plants, also known as entomophilous plants, often have these characteristics to attract insects such as bees, butterflies, and moths, which play a significant role in their pollination process.

Tassels in the corn cob represents stigma and style which wave in the wind to trap pollen grains.

Synergids are the cells of gametophyte and hence these are haploid Zygote is formed by fusion of two gametes and thus it is diploid.
Primary endosperm nucleus is formed by the fusion of diploid secondary nucleus with a male gamete. Therefore, it is triploid.

The correct answer is Option B : A is true but R is false.
Assertion A is true. In gymnosperms, the pollen grains are indeed released from the microsporangium and are typically carried by air currents, a method of pollination known as anemophily.
Reason R is false. Although it's true that air currents carry the pollen grains, the pollen grains do not directly reach the mouth of the archegonia in gymnosperms. Instead, they land on the ovule, where they germinate and form a pollen tube that delivers the male gametes to the egg. Therefore, a pollen tube is formed in gymnosperms, contrary to what Reason R suggests.

Among the animals, insects, particularly bees are the dominant biotic pollinating agents.

Cleistogamous flowers does not open at all. In such flowers autogamy occurs. Lack of cross pollination is a disadvantage of cleistogamy.

Mostly nucellus is consumed after fertilisation due to absorption of food by developing embryo in a seed. Sometimes, the nucellus remains persistent in the seed and is called perisperm.

(b) There is no need to emasculate unisexual flowers of the selected female parent - This statement is correct because unisexual flowers do not have male reproductive parts (stamens), so there is no need to remove anthers (emasculate) to prevent self-pollination.
(c) Emasculated flowers are to be bagged immediately after cross-pollination - This statement is correct because, after cross-pollination with the desired pollen, the flowers need to be bagged to prevent further contamination from unwanted pollen or other pollinating agents.
(d) Emasculated flowers are to be bagged after removal of anthers - This statement is correct. The emasculated flowers should be bagged after anther removal and before cross-pollination. This prevents contamination with unwanted pollen. After cross-pollination, the flowers should be bagged again to avoid any further contamination.

The other options are incorrect :
(a) The female flower buds of plant producing unisexual flowers need not be bagged - This statement is incorrect because even unisexual flowers need to be bagged to prevent contamination from unwanted pollen or other pollinating agents.
(e) Bisexual flowers, showing protogyny, are never selected for cross - This statement is incorrect because protogyny (when the female reproductive part matures before the male reproductive part) can reduce the chances of self-pollination, making these flowers suitable for cross-pollination.

The egg apparatus of an embryo sac consists of one egg cell and two synergids.

Whereas the embryo sac consists of one egg cell, two synergies, three antipodals and two polar nuclei.

As per the question none of the option is correct however considering the composition of embryo sac the correct option should be 2.

The transfer of pollen grains that are shed from the anther to the stigma of a pistil is termed pollination. It is of the following types:
Autogamy: Pollination is achieved within the same flower. Some plants such as Viola, produce two types of flowers. One type of flowers has exposed anthers and stigma and are referred to as chasmogamous flowers. The other type do not open at all and are referred to as cleistogamous flowers.
Geitonogamy: Transfer of pollen grains from the anther to the stigma of another flower of the same plant. Since the pollen grain comes from the same plant, it will be genetically similar to the stigma.
Xenogamy – Transfer of pollen grains from anther to the stigma of a different plant. This is the only type of pollination which during pollination brings genetically different types of pollen grains to the stigma.

Hence, the correct option is C.
NCERT Reference: Page no. 28 of topic “2.2.3 Pollination” of chapter 2.

Line in NCERT: "Xenogamy - Transfer of pollen grains from anther to the stigma of a different plant (Figure 1.9b). This is the only type of pollination which during pollination brings genetically different types of pollen grains to the stigma."

There is a characteristic distribution of the cells within the embryo sac. Three cells are grouped together at the micropylar end and constitute the egg apparatus. The egg apparatus, in turn, consists of two synergids and one egg cell. The synergids have special cellular thickenings at the micropylar tip called filiform apparatus, which play an important role in guiding the pollen tubes into the synergid. Three cells are at the chalazal end and are called the antipodals. The large central cell, as mentioned earlier, has two polar nuclei. Thus, a typical angiosperm embryo sac, at maturity, though 8-nucleate is 7-celled.

Image: 8-nucleate 7-celled embryo sac.

Hence, the correct option is C.
NCERT Reference: Page no. 27 of topic “2.2.2 The Pistil, Megasporangium (ovule) and Embryo sac” of chapter 2.

Line in NCERT: "The mature embryo sac is 7-celled and 8-nucleate."

The period for which pollen grains remain viable is highly variable and to some extent depends on the prevailing temperature and humidity.
In some cereals such as rice and wheat, pollen grains lose viability within 30 minutes of their release, and in some members of Rosaceae, Leguminoseae and Solanaceae, they maintain viability for months.

Hence, the correct option is B.
NCERT Reference: Page no. 24 of topic “2.2.1 Stamen, Microsporangium and Pollen Grain” of chapter 2.

In a majority of aquatic plants such as water hyacinth and water lily, the flowers emerge above the level of water and are pollinated by insects or wind as in most of the land plants. Their stem part which is above the thalamus is not in the water. The pollen grains are in the upper part of thalamus so pollination can't be done by water. That's why it is done by insects and wind.

Hence, the correct option is C.
NCERT Reference: Page no. 29 of topic “Agents of Pollination” of chapter 2.

Line in NCERT: "In a majority of aquatic plants such as water hyacinth and water lily, the flowers emerge above the level of water and are pollinated by insects or wind as in most of the land plants."

Explanation of the correct option:

1. A seed is an ovule that has matured morphologically.
2. Gymnosperms and angiosperm spermatophytes both exhibit seeds as a feature.
3. The seed essentially contains an embryo or the little future plant.
4. The anther contains pollen grains which help in pollination.
5. Pollen grains are haploid (n) and gametophyte, which are present inside the anther, that is diploid and sporophyte (2n).
6. The embryo sac is present in the ovule.
7. The embryo sac is a haploid (n) and gametophyte, which is present inside the ovule, which is diploid and sporophyte (2n).

Line in NCERT: "At the micropylar end is the egg apparatus consisting of two synergids and an egg cell. At the chalazal end are three antipodals. At the centre is a large central cell with two polar nuclei."

In most plants, by the time the fruit develops from the ovary, other floral parts degenerate and fall off. However, in a few species such as apple, strawberry, cashew, etc., the thalamus also contributes to fruit formation. Such fruits are called false fruits. 

Hence, the correct option is A.

Topic in NCERT: False Fruits

Line in NCERT: "However, in a few species such as apple, strawberry, cashew, etc., the thalamus also contributes to fruit formation. Such fruits are called false fruits."

• Vallisneria is an aquatic plant. In case of Vallisneria water is the agent for cross pollination. 
• In female Vallisneria, the flower reaches to the surface of water by the long stalk and the male flower or pollen grains are released into the surface of water. 
• Female flowers or stigma carried them by water current.
• Some of them eventually reach the female flowers and the stigma.

​​​​​​​Hence, the correct option is C.
​​​​​​​NCERT Reference: Page no. 29 of topic “Agents of Pollination” of chapter 2.

Line in NCERT: "In Vallisneria, the female flower reach the surface of water by the long stalk and the male flowers or pollen grains are released on to the surface of water. They are carried passively by water currents; some of them eventually reach the female flowers and the stigma."

Nucellus is the mass of parenchymatous cells enclosed within integuments of an ovule. It is the storehouse of abundant food reserves. The residual, persistent nucellus in the seed is called perisperm.
Chalaza is the basal part of the ovule, hilum is the junction between ovule and funicle and tegmen is the inner layer of the seed coat in a dicotyledonous seed.

Hence, the correct option is C.
NCERT Reference: Page no. 36 of topic “2.4.3 Seed” of chapter 2.

Line in NCERT: "this residual, persistent nucellus is the perisperm."

Autogamy and geitonogamy are two forms of self-pollination. In autogamy, pollen falls on the stigma of the same flower. While in geitonogamy pollens from a flower fall on the stigma of some other flower on the same plant. Papaya is a dioecious plant thus both autogamy and geitonogamy are prevented in it.

Hence, the correct option is B.
NCERT Reference: Page no. 31 of topic “Outbreeding Devices” of chapter 2

Line in NCERT: "In several species such as papaya, male and female flowers are present on different plants, that is each plant is either male or female (dioecy). This condition prevents both autogamy and geitonogamy."

Exine of pollen grain is made up of highly resistant fatty substance called sporopollenin, which is not degraded by any enzyme. It is not affected by high temperature, strong acid or strong alkali. Because of the sporopollenin, pollen grains are well preserved as microfossils.

Hence, the correct option is D.
NCERT Reference: Page no. 23 of topic “2.2.1 Stamen, Microsporangium and Pollen Grain” of chapter 2.

Line in NCERT: "Pollen grains are well-preserved as fossils because of the presence of sporopollenin."

• Double fertilisation is a unique and universal feature of angiosperms. Total number of nuclei involved in double fertilisation is five, i.e., 2 in syngamy and 3 in triple fusion. 
• Syngamy is fusion of one male gamete with egg to form zygote. 
• Triple fusion occurs when the second male gamete fuses with 2 polar nuclei or secondary nucleus to form triploid primary endosperm nucleus.

Hence, the correct option is D.
NCERT Reference: Page no. 34 of topic “2.3 DOUBLE FERTILISATION” of chapter 2.

Line in NCERT: "Since two types of fusions, syngamy and triple fusion take place in an embryo sac the phenomenon is termed double fertilisation, an event unique to flowering plants."

• Pollen grains of different species can land on the stigma, but pistil has an ability to recognise the compatible pollen and accept it for germination on stigma and growth of pollen tube in the style.
• There occurs a chemical mediated interaction between pollen and pistil, which facilitates the recognition and acceptance of the right type of pollen for further processes and the rejection of the wrong type of pollen grains.

Hence, the correct option is A.
NCERT Reference: Page no. 31 of topic “Pollen-pistil Interaction” of chapter 2.

Line in NCERT: "Many insects may consume pollen or the nectar without bringing about pollination. Such floral visitors are referred to as pollen/nectar robbers."

• The tapetum is a specialized layer of nutritive cells found within the sporangium, particularly within the anther, of flowering plants, where it is located between the sporogenous tissue and the anther wall.
• Tapetum is important for the nutrition and development of pollen grains, as well as a source of precursors for the pollen coat, however it does not help in dehiscence of the anther.

Hence, the correct option is A.
NCERT Reference: Page no. 21 of topic “2.2.1 Stamen, Microsporangium and Pollen Grain” of chapter 2.

Line in NCERT: "Tapetum possess dense cytoplasm and generally have more than one nucleus."

The synergid cell wall forms a highly thickened structure called the filiform apparatus at the micropylar end, consisting of numerous finger-like projections into the synergid cytoplasm. It is believed to play a major role in pollen tube guidance and reception.

Hence, the correct option is C.

Topic in NCERT: Embryo Sac Structure

Line in NCERT: "The synergids have special cellular thickenings at the micropylar tip called filiform apparatus, which play an important role in guiding the pollen tubes into the synergid."

Pollination through the agency of animals is called zoophily. The most common type of animal pollinators are insects (entomophily). Others can be birds (ornithophily), bats (chiropterophily), snails (malacophily), humans, etc.

The animal pollinated flowers have some particular characteristics in common like large (if the flowers are small in size or inconspicuous, they cluster together into an inflorescence to make them conspicuous) and brightly coloured flowers (in plants pollinated by bats, they are dull coloured), they secrete specific odours depending on the pollinator to attract them. These are some of the mechanisms that plants employ to attract pollinators.

Floral fragrance, size and colour are mechanisms employed by plants to attract specific pollinators.

Calcium crystals in microscopic forms are found in plant tissues as a defence mechanism against herbivory (the consumption of plants and plant materials by animals).

Protein pellicle in pollen tubes helps in the pollen-pistil interaction in many plants.

The stigmatic exudes are oily, mucilaginous and sticky substances that help in the process of adherence of pollen grains to stigma. It is a mechanism for the success of pollination.

The floral rewards include mostly nectar and edible pollen grains.

Line in NCERT: "Nectar and pollen grains are the usual floral rewards."

• Ovule is an integumented megasporangium found in spermatophytes which develops into seed after fertilization.
• An angiospermic ovule is typically an ovoid and whitish structure. It occurs inside the ovary where it is attached to a parenchymatous cushion called placenta either singly or in a cluster.
• The ovule is stalked. The stalk is called funiculus or funicle. The point of attachment of the body of the ovule with the funiculus is known as hilum. It is present as a scar on a mature seed.

Hence, the correct option is D.
NCERT Reference: Page no. 25 of topic “2.2.2 The Pistil, Megasporangium (ovule) and Embryo sac” of chapter 2.

Line in NCERT: "The body of the ovule fuses with funicle in the region called hilum."

Honey is made from nectar and pollens. Bees collect pollen and nectar in the spring when most flowers and plants are in bloom. They collect them in their stomach but for an hour, the nectar mixes with the proteins and enzymes produced by bees, which convert nectar into honey. 

Hence, the correct option is C.
NCERT Reference: Page no. 30 of topic “Agents of Pollination” of chapter 2.

Line in NCERT: "Pollen grains are rich in nutrients. It has become a fashion in recent years to use pollen tablets as food supplements. In western countries, a large number of pollen products in the form of tablets and syrups are available in the market."

• Geitonogamy involves transfer of the pollen from one flower of a plant to the stigma of another flower of the same plant.
• As the pollen has to move from one flower to another flower, it requires a pollinating agent. Yet it is genetically similar to autogamy, as both the flowers of the plant share the same genotype of the plant.
• Xenogamy is pollination between two flowers of two different plants.
• Apogamy: It can be defined as the development of a sporophyte directly from the gametophyte without the intervention of sex organs and gametes. The sporophyte formed usually has the same chromosome number as the gametophyte (i.e. the haploid number for the species). It is common and wide spread phenomenon in ferns.
• Cleistogamy or automatic self-pollination describes the trait of certain plants to propagate by using non-opening, self-pollinating flowers. Especially well known in peanuts, peas, and beans. 

Hence, the correct option is D.
NCERT Reference: Page no. 28 of topic “2.2.3 Pollination” of NCERT.

Line in NCERT: "Although geitonogamy is functionally cross-pollination involving a pollinating agent, genetically it is similar to autogamy since the pollen grains come from the same plant."

• Filiform apparatus helps in the entry of pollen tube into a synergid in the ovule.
• Filiform apparatus is in the form of finger like projection comprising a core of micro fibrils enclosed in a sheath. It resembles transfer cells meant for short distance movement of metabolites.
• It is responsible for the absorption of food from the nucleus.

Hence, the correct option is D.

Topic in NCERT: Pollen-pistil interaction

Line in NCERT: "Many recent studies have shown that filiform apparatus present at the micropylar part of the synergids guides the entry of pollen tube."