MEASUREMENTS

The following table may be downloaded and used as a template for collecting data.

SUMMARY TABLE OF MEASUREMENTS
PARAMETER Cold
High CO2		 °C
air 		 Warm
High CO2		 °C
air
Temperature (°C)
pH
O2 (mg/l)
O2 (% saturation)
Leaf number
Leaf size - Average for 5 leaves
Plant weight (g)
Morphological observations (average number of stomates 
on leaf area, Krantz anatomy)

Suggestions for Post Measurement Analyses:

1. Calculation of photosynthetic rates from changes in biomass or changes in leaf size (length or distance from hole punched)

2. Calculation of photosynthetic rates from changes in O2 and CO2

3. Graph changes in photosynthesis over time for different treatments

4. Graph changes in leaf number for different treatments over time

5. Graph changes in oxygen and CO2 over time in different systems

6. Graph changes in plant weight over time in different systems
 

Calculations

1. CO2   concentrations from pH change

       !!!  CO2(gas) = CO2  (dissolved) + H2O = H2CO3   = H+  + HCO3 –

       pH = -log [H+]

       pH = pK + log[HCO3-] – log [ CO2  ]

2.  Rate of primary production. The production rate of organic matter by photosynthesis can be measured by changes in biomass, changes in oxygen produced, or changes in CO2 uptake.  These are subsequently expressed in units of carbon or energy per unit time and normalized per unit area, per volume or chlorophyll content.

        By measuring changes in biomass we can express net photosynthesis in g carbon/plant (or leaf
        area)/time. Thus to calculate:  g carbon(T1) - g carbon(T0) /plant/ (T1 – T0).
 

        When measuring primary productivity one needs to distinguish between the following:

        Gross photosynthesis (Pg)=  the total fixation of energy by photosynthesis.

        Net photosynthesis (Pn) =  the actual rate of production of new biomass .  This is essentially gross
        photosynthesis minus the rate of respiration.

        Pnet = Pgross – Respiration

3. Another parameter which is used to compare the ability of different plants to convert available light energy to biomass is photosynthetic efficiency .  This is the ratio (expressed as %) of above-ground net primary production to the incoming photosynthetically active radiation (i.e. –light absorbed between 400 to 700 nm).

    To calculate: convert primary production to units of energy and divide by the light energy (measured as µmol quanta m-2 d-1
    and converted to cal m-2 d-1.)

    1 µmol quanta = 0.052 cal
    1 cal = 4.184 J
    Assume 1g dry weight = 4000 calories

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Technical contact: lpt@woodrow.org