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

The egg cell (part of the egg apparatus) is fertilized by one of the male gametes, forming the zygote, which then develops into the embryo. The NCERT text describes the egg apparatus consisting of 'two synergids and one egg cell'.

The NCERT text states: 'in some 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. Occurrence of more than one embryo in a seed is referred to as polyembryony'.

Though not explicitly detailed in the provided excerpts, the 'triple fusion' question (Question 11 from the NCERT exercise: 'What is triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion.') implies the formation of the primary endosperm nucleus from the fusion of a male gamete with the two polar nuclei in the central cell. This primary endosperm nucleus then develops into the endosperm, which provides nourishment to the developing embryo.

The introductory text mentions 'the end products of sexual reproduction, the fruits and seeds.' General biological understanding (and implied by the NCERT structure) is that the entire ovule, after successful fertilization, matures into a seed. The other options are parts of the ovule or its attachment.

While the direct formation of endosperm is not detailed in the provided excerpts, the context of sexual reproduction and the mentioned 'triple fusion' in an NCERT question highly infer the endosperm's role. It is a well-established fact that endosperm provides nutritive tissue for the developing embryo.

The NCERT sections describe 'Embryo sac formation' (Megasporogenesis and Megagametogenesis), then 'Pollination' for gamete transfer, leading to 'Pollen-pistil interaction' and finally 'Fertilization.' After fertilization, the 'Post-fertilisation: Structures and Events' lead to fruit and seed development. So, embryo sac formation precedes pollination, which precedes fertilization, followed by fruit and seed development.

The process of double fertilization involves two main fusions. One male gamete fuses with the egg cell to form the zygote, and the other male gamete fuses with the two polar nuclei in the central cell to form the Primary Endosperm Nucleus (PEN), which develops into the endosperm. This is a characteristic feature of angiosperm fertilization.

The Primary Endosperm Nucleus (PEN) is formed by the fusion of one male gamete (haploid, n) with the two polar nuclei (each haploid, n) present in the central cell. Therefore, the resulting PEN is triploid (n + n + n = 3n).

According to the process of double fertilization, one of the two male gametes released by the pollen tube fuses with the egg cell. This fusion is called syngamy or generative fertilization and leads to the formation of the diploid zygote.

The NCERT text states: '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.'