Photosynthesis and plant growth | Year 9 Biology (Cambridge) PDF Download

Photosynthesis

• Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy stored in glucose.
• Process: Chlorophyll in plant cells absorbs light energy, which is used to split water molecules into oxygen and hydrogen. The oxygen is released as a byproduct, and the hydrogen combines with carbon dioxide to form glucose.
  • Example: In a garden, plants like roses undergo photosynthesis to produce sugars from sunlight, which they use for growth and flowering.

Plant Growth

• Plant growth is a dynamic process influenced by various environmental factors and internal mechanisms.
• Environmental Factors: Factors such as light intensity, temperature, water availability, and nutrient levels play crucial roles in plant growth.
  • Example: Plants in a greenhouse grow faster due to controlled conditions that optimize factors like temperature and light.
• Internal Mechanisms: Hormones like auxins and gibberellins regulate plant growth, influencing processes such as cell elongation and fruit development.
  • Example: In tomato plants, gibberellins help in fruit enlargement, affecting their growth and development.

Transport of Water and Mineral Salts in Plants

• Plants absorb water and mineral salts from the soil through their roots and transport them to the rest of the plant.
• Root Structure: Root hairs and the root cortex increase the surface area for water absorption and facilitate the movement of minerals.
  • Example: Trees like oak trees have deep root systems that allow them to access water deep underground, helping them survive dry conditions.
• Transport Mechanism: Water moves through the plant via the xylem, driven by transpiration and cohesion-tension mechanisms.
  • Example: Cut flowers placed in a vase absorb water through their stems, demonstrating how water transport sustains plant tissues.

Conclusion

• Understanding the processes of photosynthesis and plant growth, as well as the transport of water and minerals, is essential for comprehending the biology of plants and their role in ecosystems.
• Ecological Impact: Photosynthesis not only provides energy for plant growth but also produces oxygen, which is vital for the survival of other organisms.