Sexual Reproduction in Flowering Plants MCQs for NEET — Botany Questions with Answers

Sporopollenin is a fatty substance present in the exine of pollen grains. It is resistant to microbial and chemical decomposition and can withstand the extreme environmental conditions. Due to presence of sporopollenin, pollen grains are well preserved during fossilization.

Commellina benghalensis or kankauoa bears aerial, chasmogamous (stigma and anthers exposed to pollinating agents), insect pollinated flowers and underground cleistogamous flowers. Cleistogamous flowers are bisexual flowers which never open, i.e., always remain closed. In such flowers the anthers and stigma lie very close to each other. When anthers dehisce in the flower buds, pollen grains come in contact with the stigma of the same flower, i.e., autogamy occurs. So, these flowers produce assured seed set, even in the absence of pollinators.

The coconut water obtained form the tender coconut is nothing but free nuclear endosperm (made up of thousands of nuclei) and the surrounding white kernel is the cellular endosperm.

Filiform apparatus is finger-like projection of the cell membrane of synergids or help cells at the micropylar end of the ovule. Filiform apparatus is rich in polysaccharides and chemottracts pollen tube towards micropyle.

The outermost cell layer of the endosperm (3n) of seed is called aleurone layer. Since the cells of aleurone layer are triploid, the number of chromosomes would be = 63, as root tip cells (2n) has 42 chromosomes.

Pollination by wind (anemophily) is more common amongst abiotic pollinations. Wind pollination is quite common in grasses.

Occurrence of more than one embryo in a seed is referred as polyembryony. In many Citrus and mango varieties, some of the nucellar cells surrounding the embryo sac start dividing, protrude into the embryo sac and develop into the embryos in such species each ovule contains many embryos (nucellar polyembryony).

Bisexual flowers which remain always closed are called cleistogamous and such condition of flowers is called cleistogamy. In such flowers, the anthers and stigma lie close to each other. When anthers dehisces in the flowers buds, pollen grains come in contact with stigma to effect pollination. Thus, cleistogamous flowers are invariable autogamous.

Geitonogamy (Greek geiton = neighbour and gameiu = to marry) involves the transfer of pollen grains from a male flower to the stigma of another female flower originating on the same plant. Thus, geitonogamy operates only in monoecious plants, ie, plants having male and female flowers on different places but on the same plant, eg, maize (Zea mays). In animal pollinated system, this is accomplished by a pollinator visting multiple flowers on the same plants. It is also possible within species that are wind pollinated.

Pollination taking place by means of wind is known as anemophily, eg, Zea mays, Cannabis, Pinus, etc. Some features of wind pollinated flowers are -

(i) Non-essential whorls such as calyx, corolla and bracts, bracteoles are not showy.

(ii) The perianth lobes are undeveloped or reduced and sometimes absent.

(iii) Flowers are devoid of scent and nectars.

(iv) Plants produce a very large quantity of dusty pollen grains.

(v) Pollen grains are dry, very small sized, non-sticky and unwettable

These feature are helpful for individuality of pollen grains.