Test: Post-Fertilization Events& Apomixis (October 21) - NEET MCQ

Double fertilization is the fusion of two male gametes brought by a pollen tube to two different cells of the same female gametophyte in order to produce two different structures. It is found only in angiosperms where it was first discovered by Nawaschin in 1898 in Fritillaria and Lilium. Out of the two male gametes one fuses with egg or cosphere to perform generative fertilization. Generative fertilization is also called syngamy or true fertilization. It give rise to a diploid zygote or cospore. the second male gamete fuses with the two haploid polar nuclei or diploid secondary nucleus of the central cell to form a triploid primary endosperm nucleus (PEN). This second fertilisation is called vegetative fertilisation.

In coconut (Cocos nucifera), the surrounding white kernel called coconut meal is cellular endosperm and the coconut water (also called coconut milk) in the centre is free nuclear endosperm made up of thousands of nuclei.

Endosperm represents the food storing tissue of a seed. It is produced as a result of double fertilisation in angiosperms. In most monocots and some dicot seeds, the food reserve remains in the endosperm. They are called endospermic or albuminous seeds, e.g., maize, wheat, castor bean, coconut, barley, rubber. However, in the majority of dicot seeds(e.g., orchids, Sagittaria), the endosperm is consumed during seed development and the food is stored in cotyledons and other regions. They are called non endospermic or exalbuminous seeds.

• Coeorhiza: The protective sheath covering the radicle in a germinating seed.


• Coleoptile: The protective sheath covering the plumule in a germinating seed.


• Radicle and plumule: These are the parts of the embryo in a seed.


• Radicle: The radicle is the embryonic root of the plant.


• Plumule: The plumule is the embryonic shoot of the plant.


• Therefore, coeorhiza covers the radicle and coleoptile covers the plumule.


• Hence, the correct pair is radicle, plumule.

During the development of dicot embryo, initially the dicot embryo is globular and undifferentiated. Early embryo with radial symmetry is called proembryo. It is transformed into embryo with the development of radicle, plumule and cotyledons. Two cotyledons differentiate from the sides with a faint plumule in the centre. At this time the embryo becomes heart-shaped. Part of embryo axis between the plumule and cotyledonary node is epicotyl (above the level of cotyledons) while the part between radicle and cotyledonary node is called hypocotyi (below the level of cotyledons). The single cotyledon of monocotyledonous seed {e.g. maize grain) is called scutellum. It occupies the major portion of the embryo regions of grain.

Given figure represents the monocotyledonous embryo of a grass.

Correct option is D. A-Seed coat, B-Endosperm, C-Cotyledon, D-Hypocotyl

In some seeds, remains of nucellus persist. This residual nucellus which persists in the seed is called perisperm, e.g., black pepper, coffee, castor, cardamum, Nymphaea.

In angiosperms. Endosperm is a triploid (3n) structure
∴ 3n = 24, then n = 8
Root represents is the diploid structure of a plant, therefore 2n = 16

In angiosperms, endosperm is a triploid structure.
∴ 3n = 24 (given), then n = 8
As gametes are haploid structures, therefore number of chromosomes in gametes is 8