| Date | May 2011 | Marks available | 1 | Reference code | 11M.3.SL.TZ2.7 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Describe | Question number | 7 | Adapted from | N/A |
Question
The effect of temperature on photosynthesis was studied in sweet orange (Citrus sinensis) using leaf discs. The production of oxygen was used to measure the rate of photosynthesis. Gross photosynthesis refers to the sum of net photosynthesis and respiration. Net photosynthesis was calculated by subtracting the rate of respiration in the dark from gross photosynthesis.
Identify the optimum temperature for photosynthesis in this plant.
Determine the difference between gross photosynthesis and net photosynthesis at 40°C and 50°C.
40 °C: ................................................................
50 °C: ................................................................
Deduce what happens to the rate of respiration as the temperature increases between 40°C and 50°C.
Describe the general pattern of change in photosynthesis in sweet orange as the temperature increases.
Compare the effect of temperature on photosynthesis with the effect of temperature on respiration in sweet orange.
Markscheme
40°C
40° C : 3.5 μmol m–2 s–1; (units required)
Accept answers between 3.0 μmol m–2 s–1 and 4.0 μmol m–2 s–1.
50° C : 10 μmol m–2 s–1; (units required)
Accept answers between 9 μmol m–2 s–1 and 11 μmol m–2 s–1.
rate of respiration is increasing
rate increases as the temperature increases up to a point/40°C and then decreases
at low temperatures/between 25°C and 35°C the rate of photosynthesis increases and the rate of respiration is (approximately) constant;
between 35°C and 40°C both increase;
as temperature continues to increase the rate of photosynthesis reaches optimum whereas rate of respiration decreases less/stays constant/increases;
at high temperatures/between 40°C and 50°C photosynthesis decreases as respiration decreases less/stays constant/increases;
Examiners report
C1 was well answered by most candidates.
C1 was well answered by most candidates.
C1 was well answered by most candidates.
C1 was well answered by most candidates.
C1 was well answered by most candidates.
