Figure 9. Carbon dioxide concentration before and after darkening the plant’s environment (top) and after oxygen enrichment (bottom)

From

Low-cost Spectroscopy: Experiments in Various Spectral Ranges

Patrick Gräb, Ekkehard Geidel, Hans-Christian Schmitt

World Journal of Chemical Education. 2021, 9(4), 144-151 doi:10.12691/wjce-9-4-7