Red edge

Red edge refers to the region of rapid change in reflectance of chlorophyll in the near infrared range. Vegetation absorbs most of the light in the visible part of the spectrum but is strongly reflective at wavelengths greater than 700 nm. The change can be from 5% to 50% reflectance between 680 nm to 730 nm. This is an advantage to plants to avoid overheating during photosynthesis.

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The red edge accounts for the brightness of foliage in infrared photography. It is used in remote sensing to monitor plant activity and could be useful to detect light-harvesting organisms on distant planets.

References

• Seager, S., Turner, E. L., Schafer, J., & Ford, E. B. (2005) ``Vegetation's Red Edge: A Possible Spectroscopic Biosignature of Extraterrestrial Plants Astrobiology, Volume 5, Issue 3, pp. 372-390. (link and preprint)

See also

• Purple Earth Hypothesis