Plant Physiology (Biology 327) - Dr. Stephen G. Saupe; College of St. Benedict/ St. John's University; Biology Department; Collegeville, MN 56321; (320) 363 - 2782; (320) 363 - 3202, fax; ssaupe@csbsju.edu |
Lab #1: Measuring Photosynthesis With a Qubit CO2 Gas Analyzer
Objectives:
Methods:
In today's lab we will follow the procedures given by Dr.
Diane Robertson in Part I of her
Intermediate Lab 1. We will compare the rate of photosynthesis
in a C3 (bean) and C4 (maize) plant. We will express the results on the
basis of fresh weight and per unit chlorophyll.
- Prepare 3 leaf disks using a cork borer or hole punch
- Weigh the disks (record data in table 2)
- Put the disks in a mortar and add a small amount of buffered 80% acetone
- Grind the disks thoroughly with a pestle
- Transfer the grindate to a centrifuge tube. Rinse the mortar with a small amount of fresh 80% acetone. Repeat until green color is gone. Stopper and spin at the highest setting for 5 minutes
- Pour the supernatant into a graduate cylinder. Add fresh 80% acetone to yield a final volume of 10 mL
- Record the absorbance at 645 and 663 in Table 2. Use Licthenthaler's and Welburn's equations to calculate chlorophyll concentrations.
- Complete Table 2.
Results:
Table 1. IRGA results | ||
Species | Corn | Bean |
Air temperature (C) | ||
flow rate (mL min-1) | ||
flow rate (L sec-1) | ||
Leaf area (cm2) Note: Area equals 9 cm2 if leaf fills the entire chamber. For smaller lvs, calculate the area using the tracing technique) | ||
Leaf area (m2) | ||
LED (μm m-2 sec-1) | ||
Light - reference (baseline) CO2 (ppm) | ||
Light - analysis CO2 (ppm) | ||
Light - Δ CO2 | ||
Dark - reference (baseline) CO2 (ppm) | ||
Dark - analysis CO2 (ppm) | ||
Dark - Δ CO2 | ||
Photosynthesis rate (μmol CO2 m-2 sec-1) | ||
Photosynthesis rate (μmol CO2 mg chl-1 sec-1) | ||
Respiration rate (μmol CO2 m-2 sec-1) | ||
Respiration rate (μmol CO2 mg chl-1 sec-1) |
Table 2. Chlorophyll Data | ||||||||
species | ||||||||
sample # | 1 | 2 | 3 | Mean | 1 | 2 | 3 | Mean |
tissue fresh weight (g) | ||||||||
final volume (mL) | ||||||||
A645 | ||||||||
A663 | ||||||||
Chl a (μg mL-1) in solution | ||||||||
Chl b (μg mL-1) in solution | ||||||||
Ttl Chl (μg mL-1) in solution | ||||||||
Chl a (μg) in leaf disks | ||||||||
Chl b (μg) in leaf disks | ||||||||
Ttl Chl (μg) in leaf disks | ||||||||
Chl a (μg g fw-1) | ||||||||
Chl b (μg g fw-1) | ||||||||
Ttl Chl (μg g fw-1) |
Postlab Assignment:
- copy of Table 1
- copy of Table 2
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Last updated:
01/07/2009 � Copyright by SG
Saupe