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The vegetation red edge (or just red edge, abbreviated VRE) is a feature of the reflectance of Earth vegetation: there is a limit (at a point near wavelength 700 nm) such that photons with shorter wavelengths (visible light) are generally absorbed and those with longer wavelengths (infrared light) are generally reflected. Sufficient such plants across the surface of a world can produce a detectable "feature" in its reflectance spectrum, i.e., a jump in power. Such a feature is a possible candidate for a biosignature for life on an extra-solar planet. Clouds or seasons might produce an observable a change in the effects of the feature, constituting additional evidence. There are only a limited number of plausible exoplanet biosignature candidates capable of being observed at stellar distances and all remain of interest.
The feature is evident in direct measurements of Earth plants, and has also shown in earthshine. There are theories regarding the reason for the red edge but no proven explanation. A mechanism such as photosynthesis requires photons within a particular energy range, and on Earth, such mechanisms are adapted to the light from the Sun that is allowed through atmospheric windows. Above some photon energy (i.e., sufficiently short wavelength), electromagnetic radiation (EMR) damages the organism's photosynthesis mechanism (for example, Earth's received ultraviolet light) and Earth plants have mechanisms to defend themselves from EMR wavelengths that are too short, such as biofluorescence. Wavelengths longer than the plants can use are not in the UV range and do not cause the type of damage that UV does, thus any danger that encourages evolution of a built-in red edge must be something else. It is possible the VRE cutoff is mere happenstance, due to the way photosynthesizing mechanisms are constructed. Or it may be to lessen the chance of heat damage: photosynthesis does not use the energy of the longer-wavelength IR but whatever such IR were absorbed would heat the plant.
On another planet, life might be similar, since abiotically-produced amino acids which could plausibly form there seem a reasonable "starting point" for the formation of organisms. A planet orbiting within the habitable zone of a similar star might receive EMR with a similar spectral energy distribution (SED), inducing the development of similar mechanisms. Dissimilar stars might result in an analogous feature but with a different cutoff wavelength.