The photosynthesis laboratory package may be used to measure photosynthesis in attached or detached leaves maintained in a sealed leaf chamber. O2 is produced by the light reactions of photosynthesis causing an accumulation of O2 in the chamber. The O2 concentration within the chamber is measured by a gas phase O2 sensor, and the rate at which O2 concentration in the chamber increases provides a measurement of the rate of photosynthesis.
Photosynthesis requires both light and CO2. Light is provided by a halogen light source, the intensity of which may be varied by a sliding dimmer control. The amount of light passing through the leaf is measured by a photosensor placed beneath the transparent leaf chamber. CO2 is supplied from a gas bag which the user inflates with exhaled breath, the breath providing sufficient CO2 (usually about 3%) to saturate photosynthesis. The concentration of CO2 in the chamber declines as it is fixed in photosynthesis, and its rate of fixation is directly related to the rate of O2 production. Eventually, the CO2 concentration declines to a level that will not support net fixation, and O2 production ceases as a consequence. At this point (the CO2 compensation point) the O2 concentration in the chamber remains stable unless processes are activated that inhibit photosynthesis or stimulate respiratory O2 consumption.
The photosynthesis package is best used to measure photosynthetic O2 production under CO2-saturated conditions, and the experiments described in the manuals reflect its capability under these optimal conditions. However, there is great scope for measuring the effects on photosynthesis of other environmental parameters such as light quantity and quality. In addition, plants may be pre-treated in various ways that affect their photosynthetic rate, and the effects of these treatments may be measured under conditions of both CO2 and light saturation.
| Support and funding provided by: |
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Andrew W. Mellon Foundation |
Instrumentation manufactured by: |
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