Page 30 - Ranger SPM 2022 Biology

Biology SPM Chapter 2 Leaf Structure and Function

Aim: To study the effect of concentrations of carbon dioxide on rate of photosynthesis
Hypothesis: As concentration of carbon dioxide increases, photosynthesis rate also
increases.
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Materials and apparatus: Water weeds (Hydrilla sp.), 0.0%, 0.04%, 0.08%, 0.12%,
0.16%, 0.2% sodium hydrogen carbonate solution, distilled water, 60 W light bulb,
500 ml beaker, water bath, boiling tube, retort stand, stopwatch and metre rule.
Result:

Concentration of sodium Total number of gas bubbles Photosynthesis rate
hydrogen carbonate solution (%) released in 5 minutes (min )
–1
0.00 0 0.0
0.04 6 1.2

0.08 10 2.0
0.12 12 2.4
0.16 18 3.6 Form 5
0.20 20 2.0

Rate of photosynthesis (min –1 ) 6.0

4.0

2.0
0.0
0.12
0.16
0.20
0.00
0.04
0.08
Concentration of sodium hydrogen
carbonate solution (%)
Discussions:
1. Sodium hydrogen carbonate solution supplies carbon dioxide to the water weeds.
2. Based on the results obtained, as the concentration of sodium hydrogen
carbonate solution increased, more gas bubbles were released per 5 minutes.
3. From the graph, when the concentration of sodium hydrogen carbonate solution
increased photosynthesis rate also increased, with the condition that light
intensity is not a limiting factor.
Conclusion:
Rate of photosynthesis increases when concentration of carbon dioxide increases.
The hypothesis was accepted.

The Effects of Different Light Colours on the Rate of Photosynthesis
1. Light colours play an important role in photosynthesis.
2. Plants only use a few types of light colours in photosynthesis.

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F5 Chapter 2.indd 225 3/29/22 4:35 PM