Factors affecting photosynthesisIB MYP Biology: Mind map

Exam questions on Factors affecting photosynthesis

1. A student in Dubai grows basil in pots on a balcony. In summer the afternoon temperature on the balcony can rise above 45 °C, and in the early morning, just after sunrise, the light is dim. The student notices that the plants grow best in the spring.
   Explain why the rate of photosynthesis of the basil falls when the temperature rises above about 40 °C.2 marks
2. A student measures the rate of photosynthesis of a plant at 25 °C in air containing 0.04% carbon dioxide. From 0 to 40 arbitrary units (au) of light intensity the rate rises in a straight line from zero, reaching a rate of 8 units at 40 au. From 40 au to 100 au the rate stays at 8 units. At 80 au she then increases the carbon dioxide concentration to 0.1%, and the rate rises to 14 units.
   Explain why the rate stayed at 8 units above 40 au, and why it then rose when the carbon dioxide concentration was increased.2 marks
3. A student investigates how light intensity affects the rate of photosynthesis of pondweed. She places a piece of pondweed in a beaker of water and shines a lamp on it from different distances. She counts the bubbles of gas released from the cut stem in one minute. She records 48 bubbles per minute at 10 cm from the lamp, 22 at 20 cm, 10 at 30 cm and 5 at 40 cm.
   Describe how the student should carry out this investigation so that her results are valid.3 marks