Primary Endosperm Cell — Triploid (3n), Precedes Embryo Development
✅ Asked in NEET 2026Which one of the following is a triploid cell?
Which one of the following is a triploid cell?
Answer & NCERT explanation
Correct answer: D — Primary endosperm cell
Synergids are haploid (n); the zygote is diploid (2n); the central cell with two polar nuclei is 2n before fertilisation. Only the primary endosperm cell, formed by triple fusion, is triploid (3n).
Read more NCERT concept on the PYQ
Endosperm development precedes embryo development. Why? The primary endosperm cell divides repeatedly and forms a triploid
ENDOSPERM DEVELOPMENT PRECEDES EMBRYO DEVELOPMENT. After double fertilisation, the central cell becomes the PRIMARY ENDOSPERM CELL (PEC), which is TRIPLOID (3n) — formed by fusion of one MALE GAMETE (n) with TWO POLAR NUCLEI (n + n). The PEC divides REPEATEDLY to form the TRIPLOID PRIMARY ENDOSPERM TISSUE that nourishes the developing embryo. Endosperm forms FIRST so that nutritive tissue is ready when the zygote begins development. Cell ploidies in the embryo sac and after fertilisation: SYNERGID = n (haploid); ANTIPODAL = n; EGG = n; CENTRAL CELL (before fertilisation, with 2 polar nuclei) = n+n; ZYGOTE = 2n; PRIMARY ENDOSPERM CELL = 3n. Only PEC is triploid — the diagnostic NEET answer.
NEET 2026 (cancelled) direct: 'which one is a triploid cell?' → PRIMARY ENDOSPERM CELL. Distractors: synergid (n, haploid), central cell (before fertilisation has 2 polar nuclei; after fertilisation BECOMES the PEC = 3n), zygote (2n, diploid). Only PEC is unambiguously TRIPLOID. Why endosperm forms first? To have nutritive tissue ready before embryo development. Endosperm types: free-nuclear (coconut water), cellular, helobial — based on cell wall timing.
The zygote is the triploid cell formed after double fertilisation, while the primary endosperm cell is diploid.
ZYGOTE = 2n (DIPLOID) — formed by syngamy (sperm + egg). PRIMARY ENDOSPERM CELL = 3n (TRIPLOID) — formed by triple fusion (sperm + 2 polar nuclei).
Synergid n, antipodal n, egg n, zygote 2n, PEC 3n. Only PEC is TRIPLOID. Endosperm forms BEFORE embryo (nutritive tissue ready).
- Primary Endosperm Cell (PEC) = 3n (triploid), formed by triple fusion of male gamete + 2 polar nuclei.
- Endosperm development PRECEDES embryo development to provide nutrition.
- Ploidies: synergid n | antipodal n | egg n | zygote 2n | PEC 3n. Only PEC is triploid.
- PEC divides repeatedly → triploid primary endosperm tissue → nourishes the developing embryo.
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