gen-define-seed-germination-requirements-and-give-one-short-work-6594

Define seed germination requirements and give one short worked example.

# Seed Germination Requirements **Seed germination requirements** are the specific environmental and internal conditions that must be met for a dormant seed to begin active growth and develop into a seedling. ## Key Requirements: 1. **Water (imbibition)** - Activates enzymes and metabolic processes 2. **Oxygen** - Needed for aerobic respiration to provide energy 3. **Suitable temperature** - Species-specific optimal range 4. **Light** - Required by some species (photoblastic seeds) 5. **Viable embryo** - Living, non-dormant embryo 6. **Permeable seed coat** - Allows water/gas exchange --- ## Worked Example: Lettuce Seeds **Species:** *Lactuca sativa* (lettuce) **Requirements:** - **Water:** Must absorb ~30-40% of seed weight - **Temperature:** Optimal 15-20°C (germination inhibited above 25°C) - **Light:** **Positive photoblastic** (requires light to germinate) - **Oxygen:** Normal atmospheric levels **Scenario:** Seeds are sown at 2mm depth in moist soil at 18°C in darkness. **Result:** Germination fails or is severely reduced because lettuce seeds require light exposure. The phytochrome system needs red light (660nm) to convert Pr → Pfr, which triggers germination. **Solution:** Sow seeds on the soil surface or at <1mm depth to allow light penetration.