Assertion & Reason Test: Sexual Reproduction in Flowering Plants - NEET MCQ

In Ophrys, the petal resembles as the female bee, but it is not for the competition between the two species. It is the example of mutualism as the male bee consider the petal as the female bee and pseudo copulates with it thus collecting the pollen.

And when this male bee pseudo copulates with another flower it transfers the pollen to it thus it helps in the pollination.

Primary sporogenous cell gives rise to microspore mother cells or pollen mother cells (PMCs). They are sporophytic in nature i.e., diploid. These cells undergo meiosis (reduction division) which gives rise to 4 microspores or pollens and this formation of microspores or pollens is called microsporogenesis. Microspores represent the beginning of the gametophytic phase and they are haploid in nature.

Fertilization occurs when one of the sperm cells fuses with the egg inside of an ovule. After fertilization occurs, each ovule develops into a seed. Each seed contains a tiny, undeveloped plant called an embryo. The ovary surrounding the ovules develops into a fruit that contains one or more seeds

Internal copulatory organs are absent in plants and thus the aid of an external agency is required for the transfer of pollen grains from the anther to the stigma.

The correct option is A Both assertion and reason are true and reason is the correct explanation of assertion.
Pollen grains are well preserved as fossils because their outer wall exine is made up of a highly resistant organic material called sporopollenin.
Sporopollenin is able to withstand high temperatures and strong acids and alkali. It cannot be degraded by any enzyme known so far.
Therefore, both assertion and reason are true and reason is the correct explanation of assertion.

The majority of angiosperms bear chasmogamous flowers, which means the flowers expose their mature anthers and stigma to the pollinating agents. There is another group of plants which set seeds without exposing their sex organs. Such flowers are called cleistogamous and the phenomenon is cleistogamy.

Cleistogamous flowers are bisexual flowers which do not open at all. Therefore they never expose the anthers and stigma.

Cleistogamous flowers produce assured seed-set even in the absence of pollinators. This is because the anther and stigma lie close to each other. When pollen is released, it comes in contact with the stigma resulting in pollination. Hence, pollinators are not required for pollination in cleistogamous flowers.

A typical microsporangium consists of two parts, outer wall and central homogeneous sporogenous tissue. Microsporangial wall has four types of layers– epidermis, endothecium, 1–3 middle layers and tapetum. The outer three wall layers perform the function of protection in the young anther and mechanism of dehiscence in the ripe anther.

Perisperm is a nutritive tissue of a seed derived from the nucellus and deposited externally to the embryo sac. It is diploid.

Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).

Explanation: Insects do visit flowers to gather honey (nectar), which is a source of food for them, so the assertion is true. The reason is also true, as the attraction of flowers can help prevent insects from damaging other parts of the plant. However, the reason is not the correct explanation of the assertion, as insects visit flowers primarily for the nectar, and the prevention of damage to other parts of the plant is a secondary benefit.

Assertion is true, but the reason is wrong because tapetum plays an important role in nourishing pollen mother cells (PMCs) or microspores.

A flower is a modified condensed shoot specialised to carry out the function of sexual reproduction in angiosperms. Like a branch, it arises in the axil of a small leaf like structure called bract. The receptacle (thalamus or torus) of a flower supports all the floral appendages (i.e., sepals, petals, stamens and carpels). The receptacle consists of several crowded nodes which are separated by condensed internodes. The fertile leaves of the shoot become microsporophylls (stamens) and megasporo phylls ( carpels) which bear anthers and ovules respectively. The anthers produce pollen grains and the ovules possess eggs.

A is true but R is wrong because in geitonogamous flower the pollen is transferred to the stigma of another flower of the same plant.

The gynoecium represents the female reproductive part of the flower consisting of pistil.

Pollen grain or microspore is the first cell of male gametophyte generation and represents immature male gametophyte generation and represents immature male gametophyte. Development of male gametophyte is precocious, that is, it begins inside the microsporangium or pollen sac. The pollen grain is shed at 2 or 3 celled stage. The liberated pollen grains are transferred to the receptive surface of the carpel (i.e., stigma) through pollination. Growth of the pollen grain further occurs over the female reproductive organs. Female gametophyte or embryo sac is an oval multicellular haploid structure which is embedded in the nucellus towards micropylar end of the ovule (or integumented megasporangium). Whole of the development of female gametophyte occurs inside the megasporangium.