Biology · Sexual Reproduction in Flowering Plants · NEET
NCERT says most zygotes divide only AFTER a certain amount of endosperm is formed. This is an adaptation to give the developing embryo assured nutrition. The endosperm is the food store, so the plant builds the food first, then starts the embryo. This is why 'endosperm development always precedes embryo development' is a favourite NEET one-liner.
Yes, for the EARLY stages. NCERT clearly states the early stages of embryo development (embryogeny) are similar in both monocotyledons and dicotyledons. The zygote gives rise to the proembryo, then globular, then heart-shaped, then mature embryo in both. They only differ LATER in the mature structure (dicots have 2 cotyledons, monocots have 1 cotyledon/scutellum). NEET often tests this 'same early, different late' point.
Zygote → Proembryo → Globular stage → Heart-shaped stage → Mature embryo. Do not swap globular and heart-shaped. Remember it as PGH (Proembryo, Globular, Heart-shaped) after the zygote.
The proembryo is the early few-celled stage formed when the zygote first divides. It comes before the globular and heart-shaped stages. In an assertion-reason or match-the-column question, note that coconut water is NOT a proembryo — coconut water is free-nuclear endosperm. NEET has used this exact trap.
The embryo develops at the MICROPYLAR end of the embryo sac, because the zygote is situated there (the egg was part of the egg apparatus at the micropylar end). The three antipodal cells are at the opposite chalazal end.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Zygote to proembryo to globular stage to heart-shaped stage to mature embryo. This order is fixed and commonly asked in NEET.
The endosperm forms first. Formation of endosperm always precedes the development of the embryo, so the embryo gets ready-made nutrition.
The early stages of embryogeny (proembryo, globular, heart-shaped) are similar in both. They differ only in the mature embryo, where dicots have two cotyledons and monocots have one.
At the micropylar end, where the zygote lies after fertilisation of the egg cell.
The zygote is diploid (2n), formed by syngamy of the haploid egg and one haploid male gamete.
