To measure the effect of light intensity on the rate of photosynthesis in leaf discs. Introduction :
The simple concept of photosynthesis is that it can occurs in the presence of light, which takes place in the chloroplasts of green plant cells. Photosynthesis can also be defined as the production of simple sugars from carbon dioxide and water causing the release of glucose and oxygen. The chemical equation for photosynthesis can be expressed as: (light) 6CO2 + 6H2O C6H12O6 + 6O2 (in the presence of chlorophyll)
Thus, in this experiment, we are required to determine the rate of photosynthesis of leaf disc. But first, we must know that, the rate of photosynthesis and the amount of oxygen produced by a plant is affected by different factors such as light intensity, temperature, amount of water and amount of CO2. Thus, we are investigating effect of light intensity on the rate of photosynthesis in leaf discs by varying the light intensity, and fixing the amount of sodium hydrogen carbonate solution and temperature.
It is predicted that as the intensity of light increases, so will the rate of photosynthesis and the amount of oxygen produced.
Reasearch question :
How does different light intensity (distance of light source from the table surface) affect the rate of photosynthesis in leaf disc? Hypothesis :
The greater the light intensity (shorter distance between light source and table surface) The higher the rate of photosynthesis in leaf discs.
VariablesWays to conductunit
IndipendantThe distance between the light source and the surface of table (light intensity)By using a meter ruler, each light intensity are represented by distance of (10, 15, 20, 25, 30 and 35) cm between the lamp and surface of the table.
DependantThe time taken for each leaf disc to rise. ( The rate of photosynthesis)By recording the time taken for leaf disc to rise starting form when light are applied using a stopwatch. The time taken for each disc to rise is recorded in minute. For data processing, the result will be converted to seconds to calculate the rate of photosynthesis. s
Controlled VariablesValue + UnitMethod to controlPossible effects on the result of experiment The number of leaf disc used for each value of light intensity.5 discsIn each beaker for different value of light intensity, and also for each trial, use exactly 5 leaf discs.Imagine if beaker for different trials each have 5 and 6 disc. When more leaf disc is used, the CO2 from hydrogen carbonate solution will be divided to 6 instead of 5 leaf discs. Thus the beaker with more leaf disc will take more time to rise than the other beaker. Thus the result can not be compared as the number of disc is not fixed and it will affect the rate of photosynthesis. The diameter (size) of leaf disc used for each value of light intensity.Approximate to 8mmAll the leaf discs used must be obtained by using the same cork borrer. The size of the cork borrer is approximate to 8mm.The same applied to the concept for number of leaf disc used. Bigger diameter will cause longer time for the leaf disc to rise. This will affect the rate of photosynthesis. The concentration of sodium hydrogen carbonate solution used.3%The concentration of solution of sodium hydrogen carbonate used must all be 3%.The use of sodium hydrogen carbonate is to provide CO2 in order for photosynthesis to occur. If a more concentrated solution is used for other beaker, that beaker will have more supply of CO2 that will cause photosynthesis to occur faster. Thus the value of rate of photosynthesis can not be compared with others since that rate of photosynthesis is higher and affected by more supply of CO2. The volume of sodium hydrogen carbonate solution used.10mlFirstly, take 20ml of 3% sodium hydrogen carbonate by using a beaker. Then take onlt 10 ml of it by...