1. Whole Plant Transpiration Lab
AP Biology
How to calculate transpiration RATE

2. STEP ONE: Calculating water loss g/day to ug/sec
Steps for measuring water loss
Calculate g of water/day lost then convert to ug/sec
grams x day x 1 hour x minute = ___________ gram/sec
day hr min sec
Now convert your answer to ug/sec Hint: 1 g = 106 ug
This answer is the amount of water lost
3. Calculate each day and write out your water LOSS in ug/sec for each day
W ______ Th _________ Fr__________
 Then do an average of all 3 days ______________ug/sec
NOW to get the cm2

3. STEP TWO: Measuring Leaf Surface Area
1. Gently remove all the leaves on your plant and lay them on the grid to calculate the total number of cm2
HINT: You may trace around the leaves on the grid and then throw the leaf away.
1 cm x 1 cm grid to use: 4 boxes equal one square centimeter
2. Total the entire surface area in cm2. ________________ cm2
3. Now take your average water loss divide it by the cm2 to get your answer for the TRANSPIRATION RATE __________ug/sec/cm2

4. Leaf Surface Area Results
Fan Plant = ______118_____ cm2 Control fan group ___172____ cm2 Dark Plant = ______136.75___ cm2 Control dark group __165.25_ cm2 Mist Plant = ___208_________ cm2 Control mist group __123.5___ cm2 Bright light plant = ___168____cm2 Control bright light group _157__cm2

5. RAW data for whole plant mass in grams
Whole Plant Transpiration Mass in grams (g)
Variable
Day 1
Day 2
Day 3
Day 4
Fan
304.4
285.6
269.7
251.8
Dark
233.7
227.3
221.4
215.9
Mist
253.9
252.8
252.4
Bright Light
286.2
249.9
216.7
183
Control

6. Average Transpiration rate ug/sec/cm2
Calculate the transpiration rate for each variable and your control group
Variable
Average Transpiration rate ug/sec/cm2
Fan
Dark
Mist
Bright Light
Control