Paper 3 : The lCO2 concentration and the rate of photosynthesis.

     Figure shows an experiment set up to determine the relationship between

     the CO2 concentration and the rate of photosynthesis. The rate of photosynthesis

     is estimated by counting the number of gas bubbles releases per minute.      

     The reading is tabulated in Table 1 below.

Sample Answer

Aim : To investigate the effects of carbon dioxide on the rate of     photosynthesis of a plant.

Variables :

i.  Manipulated : carbon dioxide concentration

ii. Responding : the distance of the water moved in a capillary tube/rate 

    of photosynthesis/number of bubbles released.

iii Constant : time, temperature ,light intensity, plant used

Hypothesis :

The higher the concentration of carbon dioxide, the higher is the rate of

photosynthesis.

Technique :

Counting the number of air bubbles released in a fixed time.

Apparatus and material:

Beaker, capillary tube, rubber tube, filter funnel, plastic ruler, retort stand,

Thread, dropper, natrium bicarbonate solution of a different concentrations: 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, Hydrilla sp.

Procedure:

1. Cut 5 cm of hydrilla sp. And put it in a beaker.

2. Pour a little sodium hydrogen carbonate solution into the beaker.

3. Invert a filter funnel over the hydrilla sp. in a beaker. Place plasticine at

    its rim to support it.

4. Connect the capillary tube to the filter funnel by using rubber tube and

    clip the metre ruler.

5. Withdraw water till a quarter of capillary tube.

6. Mark the initial water level in capillary tube.

7. Record water level after 10 minutes.

8. Repeat the experiment for solutions of sodium bicarbonate of 0.2%,

    0.3%,0.4% and 0.5%.

Presentation of Data:

Solution Concentrations (Natrium bicarbonate)	0.1%	0.2%	0.3%	0.4%	0.5%
Initial reading(cm)
Final reading (cm)
Difference(cm)
Rate of Photosynthesis (cms-1)

Conclusion:

The increase in carbon dioxide concentration will increase the rate of photosynthesis. The hypothesis is accepted.