Question 1: Define the term 'palisade mesophyll' and explain its role in photosynthesis.

Answer: Palisade mesophyll is a layer of elongated cells located beneath the upper epidermis of a leaf, containing chloroplasts; its role is to carry out photosynthesis efficiently due to high chloroplast density.

Question 2: Describe how the structure of the leaf's stomata facilitates gas exchange while minimising water loss.

Answer: Stomata are small pores surrounded by guard cells that control their opening and closing; their arrangement allows CO₂ to enter for photosynthesis while reducing water vapour loss through transpiration.

Question 3: What is the significance of the waxy cuticle on the surface of a leaf?

Answer: The waxy cuticle acts as a waterproof barrier that reduces water loss from the leaf surface.

Question 4: Identify the primary function of the vein (vascular bundle) in a leaf.

Answer: The vein transports water, minerals, and food (glucose) throughout the leaf and to other parts of the plant.

Question 5: Calculate the surface area in square centimetres of a circular leaf with a diameter of 5 cm.

Answer: Area = 3.14 × (2.5)^2 = 3.14 × 6.25 = 19.63 cm²

Question 6: Identify three variables that could affect the rate of photosynthesis in a leaf during an experiment.

Answer: Light intensity, carbon dioxide concentration, temperature.

Question 7: Explain why a leaf with a thicker cuticle might be less efficient at gas exchange.

Answer: A thicker cuticle forms a more effective waterproof barrier, which can hinder the diffusion of gases like oxygen and carbon dioxide, reducing efficiency in gas exchange.

Question 8: Describe a practical experiment to investigate the effect of light intensity on the rate of photosynthesis in leaf discs.

Answer: Insert a description of a practical experiment involving floating leaf discs in a solution with a dye or indicator, varying the light source distance or intensity, observing the rate of leaf disc floating (indicating oxygen production), and controlling variables such as temperature and CO₂ levels.

Question 9: Based on data showing that increasing light intensity from 100 to 400 lux increases the rate of photosynthesis from 2 to 8 units per hour, analyse the trend and suggest a possible reason for this pattern.

Answer: The data indicates a positive correlation between light intensity and the rate of photosynthesis, likely because higher light provides more energy for the light-dependent reactions, up to a point where other factors may become limiting.

Question 10: In the context of crop farming, explain how knowledge of leaf structure can influence the development of more efficient crop varieties.

Answer: Understanding leaf structure allows breeders to select for traits such as larger surface area, optimal stomatal density, or thicker cuticles, which can improve photosynthesis efficiency, water use, and drought resistance in crops.