Q.48 In which sequence the following structure/organ would be seen in ovule of Cycas.

A. Free nuclear ♀ gametophyte
B. Mature archegonium
C. Pollen chamber
D. Embryo
E. Seed

Choose the correct answer from the options given below:

1. C, B, A, D, E
2. A, C, B, D, E
3. B, A, C, D, E
4. A, B, C, D, E

   In Cycas ovules, structures appear in the sequence: Free nuclear ♀ gametophyte (A), Mature archegonium (B), Pollen chamber (C), Embryo (D), Seed (E). This chronological order reflects gymnosperm reproductive development from megaspore mitosis through seed maturation.

   Question Analysis

   Cycas ovules undergo orthosporic development where female gametophyte forms first from the megaspore, followed by archegonia, then pollination creates the pollen chamber, fertilization produces embryo, and ovule matures into seed.

   Option Breakdown

   • C, B, A, D, E: Incorrect. Pollen chamber (C) forms post-pollination after female gametophyte (A) and archegonia (B) already exist.

   • A, C, B, D, E: Incorrect. Archegonium (B) matures from cellular female gametophyte before pollen chamber (C) forms.

   • B, A, C, D, E: Incorrect. Mature archegonium (B) develops after free nuclear stage (A) completes wall formation.

   • A, B, C, D, E: Correct. Sequence: 1) Free nuclear divisions → 2) Archegonia formation → 3) Pollination (pollen chamber) → 4) Fertilization (embryo) → 5) Seed development.

   Correct Answer: A, B, C, D, E.

   Cycas ovule structure sequence free nuclear gametophyte archegonium pollen chamber embryo seed represents classic gymnosperm reproductive progression over 6-12 months. This extended timeline distinguishes Cycas from angiosperms.

   Developmental Timeline

   1. Free Nuclear ♀ Gametophyte (A): Functional megaspore undergoes 3 mitotic divisions → 8 free nuclei; walls form creating corpuscular endosperm.

   2. Mature Archegonium (B): 2-8 archegonia develop at micropylar end; each with 2 neck cells + egg (largest in plant kingdom).

   3. Pollen Chamber (C): Pollination → pollen grains sink to nucellar micropyle forming chamber; pollen tubes elongate.

   4. Embryo (D): Multiflagellated sperms fertilize eggs → proembryos → mature embryo with 3-6 cotyledons.

   5. Seed (E): Ovule → seed with fleshy sarcotesta, stony sclereid layer, fleshy sclerotesta.

   Stage	Structure	Timing	Key Event
   A	Free nuclear gametophyte	Pre-pollination	Megaspore mitosis
   B	Mature archegonium	Pre-pollination	Egg formation
   C	Pollen chamber	Pollination	Male gametophyte entry
   D	Embryo	Post-fertilization	Zygote development
   E	Seed	Maturation	Ovule transformation

   Exam Relevance

   NCERT linkage: Q48 tests temporal ovule anatomy crucial for gymnosperm life cycle questions. Remember A→B (pre-pollination female structures) before C→D→E (pollination to seed). Essential for CSIR-NET Botany Paper I.