Green gap
The green gap denotes the area between 490 and 620 nm in the absorption spectrum of chlorophyll a and b, in which hardly any sunlight is absorbed.
absorption
Since chlorophyll absorbs the light quanta outside this green gap in the leaves and grass, only the spectral range around 555 nm is remitted . This color stimulus causes the color valence green in humans . This explains why plants appear green to the human eye. The chemical structure of chlorophyll causes this unused energy for photosynthesis . The phylogenetic development of chlorophyll as a source of energy for higher plants was also subject to other influences. It is well known that not all animals have the same range of visibility as humans.
Ecological importance
One consequence of the green gap is that the (green) algae living on the water surface do not absorb light from this spectral range. Therefore, cyanobacteria , glaucophyta , cryptophyta and red algae can develop in deeper water layers . These use other processes to generate energy from light and, through the formation of phycobiliproteins, have adapted to the absorption of these special wavelengths.
proof
Theodor Wilhelm Engelmann proved the green gap in a bacteria test ( Engelmann bacteria test ), which was named after him. A prism served to split the spectrum of sunlight. Then he brought the filamentous green alga Spirogyra to different areas of the spectrum . Some of the algae were irradiated with red, others with blue and still others with green light. The collected amount of oxygen produced by photosynthesis showed that the spirogyra exposed to the green light were photosynthetically considerably more inactive. He also added aerotactic bacteria, the presence of which was mainly found in the blue and red areas, while the green area remained virtually free of them. Here the non-working algae do not release any oxygen.
Individual evidence
- ↑ Dieter Heinrich, Manfred Hergt: dtv atlas for ecology . dtv, Munich 1990, ISBN 3-423-03228-6 .