Microsporangium: wall layers & microsporogenesisलघुबीजाणुधानी: भित्ति परतें व लघुबीजाणुजनन

NCERT Fig 1.3b · Class 12 Biology · Chapter 1 · interactive diagram

Parts and their functions

• Epidermis (बाह्यत्वचा) — Outer wall layer — protection.
• Endothecium (अंतस्थीसियम) — Second wall layer (below epidermis). With the epidermis and middle layers it protects the anther and helps it dehisce to release pollen.
• Middle layers (मध्य परतें) — 2–3 layers between endothecium and tapetum; protective, help in dehiscence.
• Tapetum (टेपीटम) — Innermost wall layer. NOURISHES the developing pollen grains. Its cells have dense cytoplasm and generally more than one nucleus.
• Sporogenous tissue / PMC (बीजाणुजन ऊतक / पराग मातृ कोशिका) — Centre of the young microsporangium. Each cell is a potential pollen (microspore) mother cell — PMC, diploid (2n).
• Microspore tetrad (लघुबीजाणु चतुष्क) — Each PMC divides by MEIOSIS → a cluster of 4 haploid (n) microspores = microspore tetrad. This is microsporogenesis.
• Pollen grains (पराग कण) — As the anther matures and dehydrates, microspores separate and develop into pollen grains; then the anther dehisces.

Steps

1. Four wall layers: epidermis, endothecium, middle layers, tapetum. Centre = sporogenous tissue.
2. Each sporogenous cell can become a pollen mother cell (PMC, 2n).
3. Meiosis: each PMC → microspore tetrad (4 microspores, n). Tapetum nourishes them.
4. Microspores separate and become pollen grains; the mature anther dehisces.

Original diagram drawn by Simple Learning Hub, based on NCERT Fig 1.3b. Report a mistake