Ultraviolet-B (UV-B) is a band of ultraviolet radiation with wavelengths from about 280 to 315 nanometres (nm), just outside the visible-light spectrum. Plants do not use UV-B as part of photosynthetically active radiation (PAR), but they can detect it through the UVR8 photoreceptor, triggering changes in growth, pigmentation, protective compounds, and stress responses.
In sunlight, UV-B represents only a small fraction of incoming radiation, but it can strongly influence plant development. Excessive UV-B can damage DNA, proteins, and photosynthetic tissues, while moderate exposure can stimulate protective compounds such as flavonoids and anthocyanins.
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