Work station -1 Aim To investigate the effect of light intensity on the rate of photosynthesis. Method 1. Set up a boiling tube containing 45 cm³ of sodium hydrogen carbonate solution. Allow the tube to stand for a few minutes and shake to disperse any air bubbles that might form. 2. Cut a piece of the pondweed, Cabomba. 3. Use forceps to place the pondweed in the boiling tube carefully. The pondweed should be cut end uppermost. Make sure that you don't damage the pondweed, or cause the liquid to overflow. 4. Position the boiling tube so that the pondweed is 10 cm away from the light source. Allow the boiling tube to stand for five minutes. Count the number of bubbles emerging from the cut end of the stems in one minute. Repeat the count five times and record your results. 5. Calculate the mean number of bubbles produced per minute. Repeat the experiment at different distances away from the light source. Work station -2 Aim To investigate photosynthesis in areas of a leaf with and without chlorophyll Method 1. The leaf of a variegated Pelargonium is dropped in boiling water to kill and preserve it. 2. The leaf is left for 10 minutes in hot ethanol in a boiling tube to remove chlorophyll. 3. The leaf is dipped in boiling water to soften it. 4. The leaf is spread out in a Petri dish and covered with iodine solution. 5. The areas that had the chlorophyll stain blue-black. 6. The areas that had no chlorophyll remain pale. Work station 3 Aim To determine that photosynthesis only occurs in areas of a leaf exposed to the light. Method 1. Wrap silver foil around half a leaf and leave the plant in its normal position for 48 hours. 2. Remove the leaf from the plant and place in boiling water to kill and preserve it. 3. The leaf is left for 10 minutes in hot ethanol in a boiling tube to remove chlorophyll. 4. The leaf is dipped in boiling water to soften it. 5. The leaf is spread out in a Petri dish and covered with iodine solution. Results The areas that were exposed to the light stain blue-black. The areas that were covered by the silver foil remain pale. Work station -4 Photosynthesis-Elodea Lab Photosynthesis is the process by which plants take carbon dioxide from the atmosphere, add water, and use the energy of sunlight to produce sugar. Bromothymol blue is an indicator solution to those used to test for food nutrients. It starts as a blue solution in water, and turns yellow in the presence of carbon dioxide. A small piece of elodea will be introduced to a solution containing bromothymol blue and CO2. The point is to determine whether the elodea will have an affect on CO2 levels. Record the following information in your lab journal: Write the equation for photosynthesis: Write a hypothesis about what will happen to CO2 levels in a solution if an aquatic plant is photosynthesizing. If ___________________________________________, then ___________________________________. Materials :3 test tubes and caps 25 ml bromothymol blue elodea scissors straw aluminum foil labels beaker safety goggles Day 1: Procedure 1. Pour 75 mL of BTB solution in flask. 2. GENTLY start bubbling through the straw. A. Describe the color change: 3. Pour 25 mL of BTB solution from flask into each test tube. (Or enough to fill tube) 4. Now add a sprig of elodea to two test tubes. Place cap in all test tubes. Cover one tube of elodea with foil. Label tubes with group information. Let it sit in a well lit area undisturbed until tomorrow. 5. Record current observations in science journal. 6. Clean the lab area Day 2: Record your observations in science journal. Remember to describe any changes that occur: Analysis Questions 1. Bromothymol Blue is an indicator used to detect the presence of _______________________________ gas. 2. During cellular respiration, ____________________ gas is given off and turns the indicator _____________. 3. Why did you initially blow into the solution to turn it yellow?_______________________________________ 4. During the process of _________________________ in plants, the indicator if yellow from respiration will turn back to ____________________ because plants take in _______________ gas to give off ________________ gas. 5. Do you support or reject your hypothesis? What qualitative data did you use to come to your conclusion?
