Gymnosperms Notes 🌲
🌱 What are Gymnosperms?
- Meaning: “Gymnos” = naked, “sperma” = seeds → Naked seeds!
- Key feature: Ovules and seeds aren’t covered by any ovary wall (exposed before/after fertilization)
- Examples: Giant redwood trees (Sequoia), Cycas, Pinus, Ginkgo
🌿 Plant Structure
- Roots:
- Usually tap roots
- Special partnerships:
- Pinus: Forms mycorrhiza with fungi
- Cycas: Coralloid roots with \(N_2\)-fixing cyanobacteria 💙
- Stems:
- Unbranched (Cycas) or branched (Pinus)
- Leaves:
- Survive extreme temperature/humidity/wind ❄️🔥💨
- Cycas: Long pinnate leaves
- Conifers: Needle-like leaves reduce surface area
- Water-saving tricks: Thick cuticle + sunken stomata
✨ Reproduction
- Heterosporous: Makes two spore types:
- Microspores → Male gametophytes
- Megaspores → Female gametophytes
- Male cones 🟨:
- Bear microsporophylls with microsporangia
- Produce pollen grains (highly reduced male gametophytes)
- Female cones 🟩:
- Bear megasporophylls with ovules
- Ovule = Nucellus + protective envelopes
- Develop female gametophytes with archegonia
- Pollination & fertilization:
- Pollen travels by wind currents 🌬️
- Pollen tube delivers sperm to archegonia
- After fertilization:
- Zygote → Embryo
- Ovule → Naked seed 🥜
- Fun fact: Pinus has male/female cones on same tree, but Cycas has them on separate trees!
🔬 Key Differences from Other Plants
| Feature | Gymnosperms | Bryophytes/Pteridophytes |
|---|---|---|
| Gametophytes | Depend on parent plant 🌱 | Free-living (need damp shade) |
| Water for fertilization | ❌ Not needed | ✅ Required |
| Seeds | 🥜 Naked seeds | ❌ No seeds |
💡 NEET Must-Knows (High-Yield!)
- Naked seeds = Defining feature
- Heterospory: Microspores (♂) & megaspores (♀)
- Wind pollination + Pollen tube delivery
- Special roots: Coralloid roots (Cycas) & mycorrhiza (Pinus)
- Reduced gametophytes → Pollen grains (male) & retained female gametophytes
Keep studying – you’re doing great! 🌟💪
