Plant Growth and Development Notes

🔬 13.2 Differentiation, Dedifferentiation & Redifferentiation

  • Differentiation: Cells from root/shoot tips (meristems) or cambium mature to do special jobs
    • Example: Water-carrying cells (tracheary elements):
      • Lose their inner fluid (protoplasm)
      • Build super strong, stretchy walls 🧱 to move water
  • Dedifferentiation: Mature cells that stopped dividing can regain division ability
    • Example: Soft tissue cells (parenchyma) → cork cambium 🌱
  • Redifferentiation: New cells from dedifferentiated tissues mature again
    • Example in trees: Wood (xylem) or bark tissues
💡 Fun fact: Plant growth is “open” – cells from the same meristem become different structures based on location!
  • Cells near root tips → root cap cells
  • Cells at organ’s edge → skin (epidermis)

🌿 13.3 Development

Development = All changes from seed 🌰 → death ☠️ in a plant’s life

Steps in Plant Cell Development

MERISTEMATIC CELL 
→ Plasmatic growth 
→ Cell Division 
→ Expansion/Elongation 
→ Differentiation 
→ MATURE CELL 
→ Death

Plasticity 🌈

Plants change shape based on environment/life stage

  • Heterophylly (different leaves):
    • Cotton/coriander: Young vs. adult leaves look different
    • Buttercup: Air leaves vs. water leaves

Key Takeaway

Development = Growth + Differentiation
Controlled by:
– Inside factors: Genes 🧬 & chemicals (e.g., plant hormones)
– Outside factors: Light ☀️, temperature 🌡️, water 💧, nutrients

🌼 13.4 Plant Growth Regulators (PGRs)

What are PGRs?

Tiny molecules that control growth. Also called plant hormones

2 Main Groups

  1. Growth Promoters 🚀: Help cell division, flowering, fruiting
    • Examples: Auxins, Gibberellins, Cytokinins
  2. Growth Inhibitors 🛑: Manage stress, dormancy, leaf drop
    • Examples: Abscisic acid (ABA)
    • Special Case: Ethylene gas 🌫️ (mostly an inhibitor)

Discovery of PGRs 🔍

  • Auxin found by accident!
  • Darwin & son saw grass tips 🌾 bend toward light
  • Experiments proved: Tip sends signals (auxin) causing bending

⚡ NEET High-Yield Concepts

  1. Dedifferentiation → Parenchyma cells regain division ability
  2. Heterophylly (e.g., buttercup) = Example of plasticity
  3. PGR Groups: Promoters (auxins, gibberellins) vs. Inhibitors (ABA, ethylene)
  4. Auxin Discovery: Tip of coleoptile controls phototropism
  5. Development Formula: Growth + Differentiation + Environment factors
🌟 Pro tip: Sketch Fig 13.8 (cell development) & Fig 13.9 (heterophylly) for visual memory!