Edexcel iGCSE Biology-4.6 Germinating Seeds- Study Notes- New Syllabus

Germination and Utilisation of Food Reserves

🌱 Introduction

Germination = process by which a seed develops into a seedling.
Initially, the seedling cannot photosynthesise, so it relies on food reserves stored in the seed.

🍃 1. Food Reserves in Seeds

• Starch → in most cereals (e.g., wheat, maize)
• Proteins → in legumes (e.g., peas, beans)
• Fats/oils → in oilseeds (e.g., sunflower)
• Stored in endosperm or cotyledons

⚡ 2. Utilisation of Food Reserves

• Imbibition: water uptake → activates enzymes
• Enzymes break down reserves:
  • Amylase → starch → glucose → energy for respiration
  • Protease → proteins → amino acids → for new cell formation
  • Lipase → fats → glycerol + fatty acids → energy for growth
• Respiration of sugars/fats/proteins → ATP → powers cell division, elongation & differentiation

🌞 3. Transition to Photosynthesis

• Seedling grows upward → emerges from soil
• Leaves develop → start photosynthesising → own food production begins
• Dependence on stored food decreases once photosynthesis starts

📊 Summary Table

📌 Quick Recap
– Seeds store starch, protein, or fats for germination.
– Enzymes break down reserves → sugars, amino acids, fatty acids.
– Respiration → ATP for growth until leaves photosynthesise.
– Seedling becomes independent once leaves develop.