Investigation #5
Plant Pigments and Photosynthesis
Plant Pigments:
Purpose:
Rate of Photosynthesis
Purpose:
Pre-Lab Questions
•What are pigments?
•What is the electromagnetic spectrum?
•Why are leaves green?
•What colors do you expect to see?
•How does paper chromatography work?
•What variables affect the rate of photosynthesis in
living leaves?
•Design a controlled experiment to test one of the
variables from PLQ#6.
Materials:
-Chromatography paper
-Solvent (Petroleum ether/acetone solvent)
-Pencil
-Ruler
-Coin
-Different kinds of leaves
Procedure
Step 1: Prepare chromatography papers. Draw a
fine pencil line across the strip about 1.5 cm
from one end.
Step 2. Use the ribbed edge of the coin to push
the plant cells into the chromatography paper.
Step 3: Set the chromatograph paper in the
solvent.
Step4 : Stop the chromatogram and record
(Sketch) your results. When the solvent "front"
is within 2-3 cm from the top of the paper,
remove the chromatogram. Use a pencil to
quickly mark the location of the solvent front.
Step 5: Identify your pigments. Calculate the Rf
value (described below) for each pigment.
•Rf value = distance from origin to pigment
distance from origin to solvent front
Data Table
Leaf 1- Spinach
Color
Pigment1
Pigment2
Pigment3
Pigment4
Rf Value
Name of the Pigment
Photosynthetic pigments
•
•
Pigments absorb different λ of light
chlorophyll – absorb violet-blue/red light, reflect
green
 chlorophyll a (blue-green): light reaction, converts solar
to chemical E
 chlorophyll b (yellow-green): conveys E to chlorophyll a
 Caroten (yellow, orange): photoprotection, broaden color
spectrum for photosynthesis
 Xanotophyll (Yellow)