Leaf structure and factors affecting photosynthesisIB MYP Sciences: Mind map

Exam questions on Leaf structure and factors affecting photosynthesis

1. A botanist in Costa Rica examines a thin slice of a leaf under a microscope. She identifies the layers of cells, working from the upper surface of the leaf downwards, and notes the structures that allow the leaf to carry out photosynthesis.
   Explain how the waxy cuticle helps the leaf.2 marks
2. A sunflower leaf has tiny pores on its lower surface. Each pore is surrounded by a pair of guard cells that can change shape. The leaf also contains veins, which are made of xylem and phloem tissue.
   Describe the role of the phloem in the leaf.2 marks
3. A student investigates how light intensity affects the rate of photosynthesis in a piece of pondweed. She places the pondweed in a beaker of water containing dissolved sodium hydrogencarbonate. She places a lamp at different distances from the beaker and counts the bubbles of gas released from the cut stem in one minute. She records 52 bubbles per minute with the lamp 10 cm away, 30 at 20 cm, 18 at 30 cm, 10 at 40 cm and 8 at 50 cm.
   Identify the independent variable, the dependent variable and one control variable in this investigation.3 marks