Name ______
Photosynthesis Lab
Before you begin, save this Lab Report Template on your computer as LastNameAPBIOPhoto
Go to Biology Labs Online site ( and log onto the Leaf Lab
Read all the instructions below BEFORE you start! It will help if you print out this template to use as you perform the lab.
Read the Background Information on photosynthesisso that you understand the terms used in this online lab as well as how different factors may affect photosynthesis.
To start the Leaf Lab, click the START LAB link just under the Welcome to Leaf Lab title or scroll down on the left if you are in the Assignments window. Wait for the Leaf Lab to open. You will see a lab bench. You can click on the various items to see their names and functions. You will also see links to the areas to choose a leaf, measure leaf area, collect data, prepare data, and plot data. Please spend time getting comfortable with the lab interface before you start! The assignments link provides lots of details about how to run the lab interface. PLEASE READ THEM CAREFULLY BEFORE YOU START! The instructions below are simplified and provide data charts for you. Before you begin any of the experiments below, you need to Choose a Leaf and Measure Area. Instructions on how to do this are provided below:
Experiment 1a: Photosynthetic Rate in Tomato Plants (From online Assignment 1)
a.Click on Choose LeafYour choices are tomato (C3 plant), corn (C4) plant, 2 goldenrod clones (differ in sun or shade preference), 2 types of fescue grass (differ in chromosome number).
b.Select the Tomato: Please read the details about the tomato and note the pictures of the plant, the leaf, and the fruit.
c.Click on Measure Areaand follow the instructions to measure the area of the tomato leafRecord this value in Data Table 1a (in the Results Section below)This is necessary, because calculations of photosynthetic rate generated by the lab interface are expressed as value per unit area. Please read the details online!
d.Click on Add to Notes (bottom right of the leaf measurement screen) and Record in Data Table 1a in the Results section below.You will use the same leaf area for the entire experiment!
e.Click on Collect Data (top left of the screen). You will see a screen labeled Input Controls.
f.Set the Input Controls as follows for Experiment 1a:gas flow = medium (Note that it has changed from 0 ml/min to 500 ml/minUse default values for temperature (25 oC), CO2 concentration (350 ppm), and light filter (white)You will be altering light intensity throughout the experiment.
g.Note that as soon as you change the gas flow, a recording (blue line) starts moving on the white screen below the CO2 Output window. Click RECORD when the line is straight.
h.Change the light intensity to 200. You need to hit Enter after you change light intensity.Click Record when the line is straight.
i.Repeat with light intensities as indicated in the data chart below.(Remember to hit Enter when you change light intensity and click Record when the blue line is straight)
j.RECORD ALL YOUR VALUES IN THE DATA TABLE 1ain the Results Section below
k.Once you have finished recording, click Prepare DataYou will see a list of equations and a data chart
l.Click on the rows for Experiment 1 that you want to analyze and then click on the Compute button to calculate net photosynthetic rate (Hold the Shift key down and click to highlight successive rows)
m.Click on Add to NotesIn the notes view there is a button to Export Notes: Make sure your popup blocker is off to use this function!
n.Record the values for net photosynthetic rate in the data chart as well.
o.Now click on Plot Data!
p.Title your graph PS Rates vs. Light in TomatoLight intensity will be on x-axis and Photosynthetic Rate on y-axis
q.Hold down the shift key and click on the rows of data you want to include in the plot and click Plot Selected Data
r.You will see a scatter plot and a horizontal line. You need to fit the curve to the data. Do this by adjusting the controls:First, set the intercept: Use the photosynthetic rate for 0 light intensity: type in the intercept box and hit enterNext, adjust the slope and then the asymptoteYou want to minimize the Error SS (error sum of squares)Please read the details online for Fitting the CurveFor this experiment, the y-intercept indicates the rate of dark respiration, the slope provides information about photochemical efficiency, and the asymptote indicates photosynthetic saturation.
s.When you are finished, click Export Graph (make sure your popup blocker is off!) and cut and paste your graph below the data chart.
Experiment 1b: Photosynthetic Rate in Corn Plants
a.Repeat the experiment, this time using a Corn leaf.
b.Go to Select Leaf (Corn), then Measure Leaf
c.Record this value in Data Table 1b (in the Results Section below)
d.You will need to adjust the gas flow to high (5000ml/min), but all the other parameters should stay the same. Start with light intensity of 0 and record your data in the data table 1b in the Results section below.
e.Plot the data as you did for the Tomato plant and copy/paste your graph below Data Table 1b in the Results section below
f.When you are finished, click Export Graph (make sure your popup blocker is off!) and cut and paste your graph below the data chart.
Experiment 2: Sun vs Shade Plants (from online Assignment 4)
In this experiment, you will repeat what you did with Tomato and Corn plants with sun and shade clones of Goldenrod plants.
a.Repeat experiment, this time using the Goldenrod Sun leaf:
b.Go to Select Leaf (Goldenrod Sun) and Measure Area BEFORE you start this experiment
c.Record this value in Data Table 2a below
d.Go to Collect Data
e.Set the input controls as follows:gas flowmedium = (500 ml/min)temperature = 25oClight filter = white
f.Start with light intensity of 0 and record your data in the data table 2a in the Results section below.
g.Plot the data as you did for the Tomato and corn plants and copy/paste your graph below Data Table 2a in the Results section below
h.When you are finished, click Export Graph (make sure your popup blocker is off!) and cut and paste your graph below Data Chart 2a
i.Repeat with the Goldenrod Shade clone.
j.Go to Select Leaf (Goldenrod Shade) and Measure Area BEFORE you start this experiment
k.Record this value in Data Table 2b below
l.Go to Collect Data
m.Set the input controls as follows:gas flowmedium = (500 ml/min)temperature = 25oClight filter = white
n.Start with light intensity of 0 and record your data in the data table 2a in the Results section below.
o.Plot the data as you did for the Tomato and corn plants and copy/paste your graph below Data Table 2a in the Results section below
p.When you are finished, click Export Graph (make sure your popup blocker is off!) and cut and paste your graph below Data Chart 2b
Experiment 3: Influence of Light Quality (Color/Wavelength) on Photosynthesis in Corn Plants (from online Assignment 2)
a.Go to Select Leaf (Corn) and Measure Area BEFORE you start this experiment
b.Go to Collect Data
c.Set the input controls as follows:
gas flow high = (5000 ml/min)
temperature = 25oC
light filter = whiteThe light shining on the leaf corresponds to the filter color
d.Measure photosynthesis for the light values indicated in Data Table 3 in the Results Section below
e.Repeat using red, green, and blue light filters
f.Record the photosynthetic rate for each trial, using the compute function in the Prepare Data area
g.Prepare and fit separate curves of photosynthetic rate (P) vs light intensity for each light filter.Note: it is a little tricky to use the graph function on Leaf Lab to construct a multiline graph, so you may want to use GraphPad ( or Create-a-Graph ( If you use either of these sites, you don’t need to fit the curve, but you should be able to determine rates of dark respiration (y-intercept) photochemical efficiency (initial slope), and photosynthetic saturation (asymptote). Copy and paste your graph after Data Table 2 below.
Experiment 4: Effect of CO2 Concentration on Photosynthesis (from online Assignment 6)Optional
Follow the online directions for Assignment 6 to determine the effect of CO2 Concentration on Photosynthesis in C3 (Tomato) and C4 (Corn) plants
Experiment 5: Effect of Temperature on Photosynthesis (from online Assignment 7)Optional
Follow the online directions for Assignment 7 to determine the effect of Temperature on Photosynthesis in Tomato plants
Experiment 6: Influence of Polyploidy on Photosynthesis (from online Assignment 8)Optional
Follow the online directions for Assignment 8 to determine the effect of Polyploidy on Photosynthesis in 4N (tetraploid) and 8N (octaploid) Tall Fescue Grass plants
Results:
Data Table 1a: Photosynthetic Rate in Tomato Plants
Leaf Area = ______
Gas Flow (medium) = 500 ml/min Temperature = 25oC CO2 Concentration = 350 ppm Light Filter = White
Light Intensity
(umol/m2/s)
/Carbon Input
(ppm)
/Carbon Output
(ppm)
/Net Photosynthetic Rate (umol/m2/s)
0
/350
200
/350
400
/350
600
/350
800
/350
1000
/350
1200
/350
1400
/350
1600
/350
1800
/350
2000
/350
Data Table 1b: Photosynthetic Rate in Corn Plants
Leaf Area = ______
Gas Flow (high) = 5000 ml/min Temperature = 25oC CO2 Concentration = 350 ppm Light Filter = White
Light Intensity
(umol/m2/s)
/Carbon Input
(ppm)
/Carbon Output
(ppm)
/Net Photosynthetic Rate (umol/m2/s)
0
/350
200
/350
400
/350
600
/350
800
/350
1000
/350
1200
/350
1400
/350
1600
/350
1800
/350
2000
/350
Data Table 2a: Photosynthetic Rate in Goldenrod Sun Plants
Leaf Area = ______
Gas Flow (medium) = 500 ml/min Temperature = 25oC CO2 Concentration = 350 ppm Light Filter = White
Light Intensity
(umol/m2/s)
/Carbon Input
(ppm)
/Carbon Output
(ppm)
/Net Photosynthetic Rate (umol/m2/s)
0
/350
200
/350
400
/350
600
/350
800
/350
1000
/350
1200
/350
1400
/350
1600
/350
1800
/350
2000
/350
Data Table 2b: Photosynthetic Rate in Goldenrod Shade Plants
Leaf Area = ______
Gas Flow (medium) = 500 ml/min Temperature = 25oC CO2 Concentration = 350 ppm Light Filter = White
Light Intensity
(umol/m2/s)
/Carbon Input
(ppm)
/Carbon Output
(ppm)
/Net Photosynthetic Rate (umol/m2/s)
0
/350
200
/350
400
/350
600
/350
800
/350
1000
/350
1200
/350
1400
/350
1600
/350
1800
/350
2000
/350
Data Table 3: Light Quality (Color/Wavelength) and Net Photosynthetic Rate in Corn Plants
Leaf Area = ______
Gas Flow (high) = 5000 ml/min Temperature = 25oC CO2 Concentration = 350 ppm
Light Intensity
(umol/m2/s)
/Color
/PhotoSx Rate (umol/m2/s)
/Color
/PhotoSx Rate (umol/m2/s)
/Color
/PhotoSx Rate (umol/m2/s)
/Color
/PhotoSx Rate (umol/m2/s)
0
/white
/red
/ green /blue
200
/ white / red / green / blue400
/ white / red / green / blue600
/ white / red / green / blue800
/ white / red / green / blue1000
/ white / red / green / blue1200
/ white / red / green / blue1400
/ white / red / green / blue1600
/ white / red / green / blue1800
/ white / red / green / blue2000
/ white / red / green / blueDiscussion and Analysis
1.Summarize what you did and discuss what is meant by rate of dark respiration, rate of photochemical efficiency, and photosynthetic saturation.
2.Describe the relationship between light intensity and photosynthetic rate in tomato, corn, and goldenrod plants.
3.Compare/contrast the rates of dark respiration and photochemical efficiency in tomato and corn plants and in sun and shade clones of goldenrod plants
4.Compare/contrast the light intensity associated with photosynthetic saturation (maximum photosynthesis rate) in tomato, corn, and goldenrod plants.
5.Describe the relation between light quality (wavelength/filter) and photosynthesis rate in corn. Which color is associated with the lowest photosynthesis rate? Explain.
6.Describe the relation between temperature and photosynthesis rate in tomato plants.
Conclusion:
Brief statements about the effect of light intensity and color on photosynthetic rates in the different plants you studied.
Reflection: Comment on what you learned by doing this lab.