Test: Sexual Reproduction in Flowering Plants - 3 - NEET MCQ

• Apomixis in flowering plants is defined as the asexual formation of a seed from the maternal tissues of the ovule, avoiding the processes of meiosis and fertilization, leading to embryo development. 
• Apomixis relates to mechanisms where an embryo sac is mitotically formed from a diploid cell in the ovule, bypassing meiosis. The genetic nature of plants produced by apomictic embryos is the same as that of parents so they can be called clones.
• Hence, the mother cell is diploid, so diploid embryo forms.

Topic in NCERT: POST-FERTILISATION: STRUCTURES AND EVENTS
Line IN NCERT: apomixis is a form of asexual reproduction that mimics sexual reproduction. There are several ways of development of apomictic seeds. In some species, the diploid egg cell is formed without reduction division and develops into the embryo without fertilisation.

In angiosperms, the pollen grain contains a vegetative cell and a generative cell. The generative cell divides mitotically to produce two male gametes, which are necessary for fertilization. The vegetative cell does not divide to form gametes; instead, it forms the pollen tube that facilitates the transfer of the male gametes to the ovule.

Topic in NCERT: Pollen Development and Structure

Line in NCERT: "The generative cell divides mitotically to give rise to the two male gametes before pollen grains are shed (3-celled stage)."

Orchids and parasitic plants like Orobanche and Striga typically produce a large number of seeds per fruit, not just one. This high seed production is a strategy to increase the chances of successful germination and establishment in their respective environments. The other statements are true based on historical and botanical records.

Topic in NCERT: PARASITIC PLANTS

Line in NCERT: "Similar is the case in fruits of some parasitic species such as Orobanche and Striga."

Pollen wall consists of two layers: outer layer exine and inner layer intine.

Exine is made up of sporopollenin which is one of the most resistant known biological materials. Exine is thin in the beginning but it becomes very thick with maturity. However, exine is discontinuous or ruptured at some places. These are the called the germ pores (or germinal furrow) through which pollen tube comes out during germination on the stigma.

Topic in NCERT: Pollen Grain Structure and Function

Line in NCERT: "Pollen grain exine has prominent apertures called germ pores where sporopollenin is absent."

• The protoplast of the male gametophyte divides mitotically to produce two unequal cells; a small generative cell and a large vegetative cell.
• The generative cell divides into two non-motile male gametes (or sperms).
• Thus, the male gametophyte in angiosperms produces two sperms and a vegetative cell.
• The vegetative cell, later on grows to produce pollen tube.

Topic in NCERT: Pollen Development and Structure

Line in NCERT: "The generative cell divides mitotically to give rise to the two male gametes before pollen grains are shed (3-celled stage)."

• Statement 1: Pollination does not guarantee fertilization; it is merely the transfer of pollen to the stigma. Post-pollination events, including pollen-pistil interaction, must occur to ensure fertilization.
• Statement 2: The sequence of events from pollen deposition on the stigma until the pollen tubes enter the ovule is correctly referred to as pollen-pistil interaction. This statement is correct.
• Statement 3: Pollen-pistil interaction involves both the promotion and rejection of pollen, depending on compatibility. Therefore, the statement that it involves only promotion is incorrect.
• Statement 4: Pistils do have the ability to recognize pollen and can discriminate between compatible and incompatible pollen types.

Thus, Statement 2 is the correct option.
Topic in NCERT: Pollen-Pistil Interaction
Line in NCERT: "Pollen-pistil interaction involves all events from the landing of pollen grains on the stigma until the pollen tube enters the embryo sac (when the pollen is compatible) or pollen inhibition (when the pollen is incompatible)."

Hilum is the junction between the ovule and funicle (2).
Integuments are the protective envelopes encircling the nucellus (3).
Micropyle is the small opening at the tip of the ovule (1).
Chalaza is the basal part of the ovule, opposite the micropyle (4).
Nucellus is the mass of cells inside the ovule with abundant reserve food materials (5).
Therefore, the correct matches are A - 2, B - 3, C - 1, D - 4, and E - 5.
Topic in NCERT: The Megasporangium (Ovule)
Line in NCERT: "The body of the ovule fuses with funicle in the region called hilum. Thus, hilum represents the junction between ovule and funicle. Each ovule has one or two protective envelopes called integuments. Integuments encircle the nucellus except at the tip where a small opening called the micropyle is organised. Opposite the micropylar end, is the chalaza, representing the basal part of the ovule. Enclosed within the integuments is a mass of cells called the nucellus. Cells of the nucellus have abundant reserve food materials."

(C) Pollen tablets are available in the market for supplementing food. Here's why:
- Supplementing Food: Pollen tablets are commonly used as a nutritional supplement due to their rich content of proteins, vitamins, minerals, and antioxidants.
- They can enhance the nutritional value of one's diet, especially for individuals who may have specific dietary deficiencies or require additional nutrients.
- These tablets are not primarily associated with in vitro fertilization, breeding programs, or ex situ conservation, but rather serve as a dietary supplement for human consumption.
Topic in NCERT: Pollen Products
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 pea, bean and groundnut, endosperm is consumed by developing embryo in the seed. The endosperm is completely absorbed by the growing embryo and the food reserve gets stored in the cotyledons. Such seeds are called non-endospermic or exalbuminous.

Topic in NCERT: Seed

Line in NCERT: "Non-albuminous seeds have no residual endosperm as it is completely consumed during embryo development (e.g., pea, groundnut)."

Answer: B
The correct answer is: A-Meiosis-I, B-Meiosis-II, C-No division, D-Mitosis.

• A: Meiosis-I reduces the chromosome number by half, creating two haploid cells from a diploid cell.
• B: Meiosis-II separates the sister chromatids, resulting in four haploid cells.
• C: No division indicates no further cell division occurs at this stage.
• D: Mitosis produces two identical daughter cells, maintaining the chromosome number.

During microsporogenesis, meiosis occurs in Microspore Mother Cell (MMC) and four haploid microspores (microspore tetrad) are formed.

Topic in NCERT: Microsporogenesis

Line in NCERT: "Cells of the sporogenous tissue lying in the centre of the microsporangium, undergo meiosis (microsporogenesis) to form tetrads of microspores."

• The period in which the pollen grains remain viable is highly variable.
• It depends on the temperature and humidity.

Topic in NCERT: Pollen Viability and Storage

Line in NCERT: "The period for which pollen grains remain viable is highly variable and to some extent depends on the prevailing temperature and humidity."

• The diagram represents the multicarpellary, syncarpous pistil of Papaver.
• The gynoecium of this plant consists of more than one pistil, showing multicarpellary condition.
• These pistils are fused together and hence are called syncarpous.

Topic in NCERT: The Pistil, Megasporangium (ovule) and Embryo sac

Line in NCERT: "The gynoecium may consist of a single pistil (monocarpellary) or may have more than one pistil (multicarpellary). When there are more than one, the pistils may be fused together (syncarpous) or may be free (apocarpous)."

1. "Pollination by water is quite rare in flowering plants"

   • True to some extent, but this statement is incomplete and less specific. Water pollination (hydrophily) occurs in only a small number of aquatic plants.

2. "All aquatic plants use water for pollination"

   • False. Many aquatic plants, like Water Hyacinth and Water Lily, are pollinated by insects or wind, not water. Their flowers are above the water surface.

3. "In most of the water-pollinated species, pollen grains are protected from wetting by a mucilaginous covering"

   • True. In water-pollinated species (e.g., Vallisneria, Zostera), pollen grains are coated with mucilage to prevent them from getting damaged in water.

4. "Plants such as Water Hyacinth and Water Lily are pollinated by water"

   • False. Water Hyacinth and Water Lily have their flowers above water and are pollinated by insects or wind, not water.

Topic in NCERT: Pollination by Water
Line in NCERT: "Pollination by water is quite rare in flowering plants and is limited to about 30 genera, mostly monocotyledons." "In most of the water-pollinated species, pollen grains are protected from wetting by a mucilaginous covering." "Not all aquatic plants use water for pollination." "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."

• Statement 1: This is correct. Non-albuminous seeds have no residual endosperm, as it is completely consumed during embryo development, while albuminous seeds retain some endosperm.
• Statement 2: This is incorrect. The perisperm is a residual, persistent nucellus, not a type of endosperm, and is found in seeds like black pepper and beet, not wheat and maize.
• Statement 3: This is incorrect. Cotyledons are generally thick and swollen due to the storage of food reserves.
• Statement 4: This is incorrect. The micropyle facilitates the entry of water and oxygen into the seed during germination, not the exit of water.

Therefore, Statement 1 is the correct statement regarding seed characteristics and development.
Topic in NCERT: Seed
Line in NCERT: "Non-albuminous seeds have no residual endosperm as it is completely consumed during embryo development (e.g., pea, groundnut). Albuminous seeds retain a part of endosperm as it is not completely used up during embryo development (e.g., wheat, maize, barley, castor)."