the time taken by a leaf text to float a back is an indication of the rate of photosynthesis the more time taken to for all the leaf dics float up what is the rate of photosynthesis
Answers
Explanation:
In this experiment, the effect of light intensity on rate of photosynthesis was investigated by recording the time taken for the leaf discs to float at the surface of sodium hydrogen carbonate solution in the beaker. This method is more accurate than to immerse a plant and then count the number of bubbles produced per minute. This is because it is easier to observe the leaf discs which are bigger than the bubbles and there is also no need to count the number of bubbles produced at the same time which most probably lose the focus to record an accurate time.
Sodium hydrogen bicarbonate was used in this experiment to supply carbon dioxide to the pineapple leaf discs to perform photosynthesis. The water does not have a high concentration of carbon dioxide dissolved in it but the amount is sufficient for the aquatic plants to survive. Hence, by using sodium hydrogen bicarbonate will increase the concentration of carbon dioxide available for plants to produce glucose and oxygen thus, increasing the rate of photosynthesis. [3] This is important so that the time taken for the leaf discs to float on the surface will not be too long and to get a clearer result as well.
The leaf discs sink when put into the bicarbonate solution. This is because the bicarbonate solution infiltrates the air spaces of the leaf discs causing the overall density to increase. That is why the leaf discs sink. On the other hand, when the leaf discs were left in the beaker under the lamp, we had observed that the leaf discs slowly rise up to surface. The explanation for this is, when photosynthesis occur, oxygen will be released into the interior of the leaf causing the buoyancy to change. Hence, the leaf discs rise up to the surface. However, at a certain times, the leaf discs sink again. This happened as respiration process that occurs at the same time, consumed oxygen, thus it removed the oxygen from the air spaces thereby, causing the bicarbonate solution to fill in the spaces again. This therefore, results in the sinking of the leaf discs again. Since both processes took place at the same time, we can say that the result obtained is the net rate of photosynthesis. [4]
Now, to analyse further, when the experiment used white light, the graph produced has a lower rate of photosynthesis compared to that of the other colors such as red and blue light. This is because chlorophyll will only absorb light with a certain wavelength. Since, white light has various colors ranging from violet to red, thus, not all light will be absorb, thus, the source of light will not be fully utilised to perform the photosynthesis process. However, if red light is used, the graph will have a higher rate of photosynthesis as red light has the highest percentage absorbance by the chlorophyll molecules. On the other hand, if the green light is used, a graph with lower rate of photosynthesis will be produced as green light has the lowest percentage absorbance by the chlorophyll molecules. This green light in the white light is the light that is not absorbed by the chlorophyll which makes the rate of photosynthesis of the leaf discs is lower than other leaf discs under other colors of light.