Sexual Reproduction in Flowering Plants, on the exam screen.

Microsporogenesis begins with sporogenous tissue (Statement II), whose cells become pollen mother cells (Statement IV). Each pollen mother cell undergoes meiosis to form microspore tetrads (Statement I), which then separate into individual microspores that mature into pollen grains (Statement III). Hence the order is II, IV, I, III.

The primary endosperm cell forms during double fertilisation when a haploid male gamete fuses with the diploid secondary (fusion) nucleus, making it triploid (3n). Synergids are haploid, the zygote is diploid, and the central cell before fusion carries two haploid polar nuclei.

Xenogamy is cross-pollination in which pollen is transferred to the stigma of a flower on a genetically different plant, so it alone brings genetically different pollen. Autogamy (same flower) and geitonogamy (different flower of the same plant) deliver genetically identical pollen, and cleistogamous flowers are obligately autogamous.

A typical angiosperm anther is bilobed, and each lobe contains two theca - the anther is therefore described as DITHECOUS. Since each theca houses one microsporangium, the whole anther has four microsporangia arranged at its corners, two per lobe. NCERT Class 12, Sexual Reproduction in Flowering Plants.

The two synergids flank the egg at the micropylar end and bear the FILIFORM APPARATUS, a set of thickened cell wall projections that secrete chemical attractants and guide the pollen tube into the embryo sac. The pollen tube in fact enters one of the synergids, not the egg directly, and releases the two male gametes there. NCERT Class 12, Sexual Reproduction in Flowering Plants.

Non-albuminous seeds lack endosperm at maturity because it is used up during embryo development. In pea, reserve food is stored in the cotyledons.

Endosperm arises by TRIPLE FUSION, in which one male gamete fuses with the two polar nuclei, so it is triploid. With $2n = 36$, the haploid number is $n = 18$ and the endosperm is $3n = 54$. The embryo, formed by the other male gamete fusing with the egg, remains diploid at 36. NCERT Class 12, Sexual Reproduction in Flowering Plants.

The body of the ovule is fused to the funicle at the hilum. Chapter: Sexual Reproduction in Flowering Plants.

The flowers of water hyacinth and water lily emerge above the water surface and are pollinated by insects or wind, not by water currents. Chapter: Sexual Reproduction in Flowering Plants.

Pollen grains inside the anther and embryo sac inside the ovule both consist of two generations, one within the other. Pollen grains contain microspores (haploid) and the embryo sac contains the female gametophyte (haploid) within the ovule (diploid). Chapter: Sexual Reproduction in Flowering Plants.