Page 27 - Ranger SPM 2022 Biology

Biology SPM Chapter 2 Leaf Structure and Function

• Photosynthesis rate can be increased by
increasing light intensity.
• However, if light intensity is too high, the
stomata will close to reduce water loss through
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transpiration. This prevents carbon dioxide from
entering the leaf, which subsequently decreases
photosynthesis rate.

Temperature • Any changes in temperature will affect
Maximum
100 photosynthesis rate because light-independent
Photosynthesis rate (cm / min) 60 • As the temperature increases, the rate of
reactions are catalysed by enzymes.
80
photosynthesis will also increase until the optimum
temperature. Optimum temperature of most plants
40
are between 25 °C to 30 °C.
20
temperature, photosynthesis rate decreases
5 10 15 20 25 30 35 40 • At temperature higher than the optimum
Temperature (ºC) because the enzymes are denatured.

Form 5
Aim: To study the effect of light intensity on rate of photosynthesis
Hypothesis: As light intensity increases photosynthesis rate also increases
Materials and apparatus: Hydrilla sp., 0.3% sodium hydrogen carbonate solution,
distilled water, 60 W light bulb, 500 ml beaker, stopwatch, thermometer, paper clip,
blade, table lamp, metre rule, filter funnel, boiling tube, retort stand and black paper

Oxygen
Retort stand
Gas bubbles
Boiling tube
60 W
light bulb 0.2% sodium hydrogen
Beaker carbonate solution
Filter funnel
Hydrilla sp.
Metre rule
Figure 2.10 Set-up of apparatus
1. Light intensity is calculated by using the following formula:
1
Light intensity =
Distance between light source and Hydrilla sp.

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F5 Chapter 2.indd 222 3/29/22 4:35 PM