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No photosynthesis occurs in the absence of light, but the respiration continues and the net gas exchange of a green plant will show uptake oxygen and resale of carbon dioxide. As the light intensity increases, so the rate of photosynthesis increases until the amount of carbon dioxide released from respiration is equal to the amount used up in the photosynthesis. .
Carbon dioxide is needed in the light - dependent reactions, where it is involved in the formation of carbohydrates. Carbon dioxide concentration will directly affect the rate of photosynthesis as it is used in the photosynthesis reaction. It is necessary to provide the plant with sufficient amount of CO2. This can be done if the plant is placed in sodium hydrogencarbonate (NaHCO3) solution. The sodium carbonate will go through a chemical change and replace the CO2 that the plant takes from the water. The oxygen that the plant gives off as it carries on photosynthesis will be released into the water. .
Temperature affects the rate of chemical reactions and is important in the light - dependent stage of the photosynthetic process because the reactions are enzyme controlled. In temperate climates, the optimum temperature for photosynthesis is about 25°C. As the temperature is increased, molecules in the cells will be moving at a faster rate. If the temperature is raised above a certain level, the rate of photosynthesis will drop as the plant's enzymes are denatured. .
Temperature is the only factor that I will change while carrying out this lab with the help of a water bath. .
Apparatus:.
Elodea Plant - An Elodea plant is used as it is an aquatic plant. It is a plant that releases oxygen bubbles which are easy to measure. .
Photosynthometer - A photosynthometer is used to measure the uptake of oxygen bubbles into the capillary tube, as there is no other way of measuring the length of the bubbles.
Bench Lamp - This is used to maintain constant light intensity.
