Biology · Sexual Reproduction in Flowering Plants · NEET
Endosperm is triploid (3n). It forms from the primary endosperm nucleus (PEN), which is made by triple fusion: one male gamete (n) fuses with the two polar nuclei (n + n) of the central cell. So n + n + n = 3n. In a NEET question, if the diploid number is 2n = 36, then n = 18 and endosperm = 3 × 18 = 54.
In the most common type of endosperm development, the PEN divides again and again to make many free nuclei WITHOUT cell walls between them. This stage is the free-nuclear endosperm. The NCERT example is the coconut water of a tender coconut, which is free-nuclear endosperm made of thousands of nuclei.
Coconut water is the FREE-NUCLEAR ENDOSPERM, not the embryo. NCERT states clearly: 'The coconut water from tender coconut... is nothing but free-nuclear endosperm.' The white kernel around it is the cellular endosperm. The edible part (kernel) is therefore endosperm, not a cotyledon.
Free-nuclear endosperm is the early stage where nuclei form by repeated division but NO cell walls are laid down (e.g., coconut water). Cellular endosperm is the later stage where cell walls form around the nuclei, making proper cells (e.g., the white coconut kernel). The number of free nuclei formed before cellularisation varies greatly between plants.
Endosperm development ALWAYS precedes embryo development. Most zygotes divide only after some endosperm is formed. This is an adaptation to give the developing embryo an assured supply of food. This 'endosperm first' rule is a common NEET one-liner.
It depends on the seed type. In non-albuminous (ex-albuminous) seeds like pea, groundnut and beans, the endosperm is completely used up by the embryo before the seed matures. In albuminous seeds like castor, coconut, wheat, maize and barley, the endosperm persists and is used during germination.
The coconut water from tender coconut represents:
The morphological nature of the edible part of coconut is
If the diploid chromosome number of a typical angiosperm is 36, what would be the chromosome number in its endosperm?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The endosperm is a food-storage tissue. Its cells are filled with reserve food materials and are used for the nutrition of the developing embryo (and later during seed germination in albuminous seeds).
Endosperm forms first so that the growing embryo has an assured supply of nutrition. NCERT calls this an adaptation to provide assured food to the developing embryo.
Albuminous (endospermic) seeds retain endosperm in the mature seed, e.g., castor, coconut, wheat, maize, barley. Non-albuminous seeds have the endosperm fully used up during embryo development, e.g., pea, groundnut, beans.
During double fertilisation, the second male gamete fuses with the two polar nuclei of the central cell. This is triple fusion (three haploid nuclei fusing) and it produces the triploid primary endosperm nucleus (PEN).
No. Endosperm is the 3n nutritive tissue from triple fusion. Perisperm is the persistent remnant of the nucellus (diploid maternal tissue), seen in seeds like black pepper and beet.
