Factors Affecting Photosynthesis - Extended Engelmann Experiment

Investigating different factors that affect photosynthesis
Experimental setup (expand)
The Engelmann experiment investigates photosynthesis via oxygen production.
A filamentous alga (for example Spirogyra) lies in a water droplet under the microscope. White light is split into spectral colours by a prism and projected onto the alga as a coloured band, so that different wavelengths act on different parts of the alga.
Motile aerobic bacteria are added to the surrounding water. They need oxygen and therefore serve as biological indicators: where more O₂ is available locally, their distribution can change. This makes it possible to observe spatially, along the spectrum, how strongly photosynthesis proceeds under each condition,
Chart 1: light intensity Apparent photosynthesis (total): –
Chart 2: temperature Apparent photosynthesis (total): –
Chart 3: CO₂ concentration Apparent photosynthesis (total): –

Parameter

Apparent: – Actual: – Respiration: –
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–
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λ: – PS: – O₂ (rel.): – T-factor: – Light factor: – CO₂ factor: –
Legend: parameters & model assumptions (expand)
Light colour: determines how well the alga can use the light (with a prism, this depends on the wavelength across the width).
Light intensity: more light increases photosynthesis up to saturation (at very high light levels, the additional gain becomes smaller).
CO₂ supply: more CO₂ increases photosynthesis up to saturation.
Temperature: activity rises up to an optimum and then decreases; at very high temperatures it drops sharply.
Bacteria: gather where more O₂ is produced (a proxy for photosynthesis).
Charts: mouse wheel = zoom, drag = pan, double-click = reset.

Messfenster an der Lupe

Relative photosynthesis (at the magnifier position)
– %
Bacterial accumulation (magnifier)
– %
Comparison with the average in the basin: positive values indicate accumulation in the measurement window.

Log

Measurement point Light (%) CO₂ (%) T (°C) Colour Prism λ (nm) Actual (%) Respiration (%) Apparent (%)
The measurement value from the current measurement window (magnifier) is saved together with the current slider settings.