title: Elevated ultraviolet-B radiation induces cross-protection to cold in leaves of Rhododendron under field conditions.
abstract: Previously, we have shown a cold-hardening response in Rhododendron 'English Roseum' exposed to elevated ultraviolet-B radiation (UV-B, 280-320 nm) under growth chamber conditions. We have conducted the present study under field conditions to provide for a higher ratio of photosynthetically active radiation to UV-B (PAR:UV-B) than is possible in the laboratory and to more accurately reflect natural conditions of solar irradiance. Leaf disks taken after 3 months from UV-B-exposed plants exhibited a greater tolerance to freezing temperatures than those from control plants that received no supplemental UV-B exposure during this time. Leaf disks taken from UV-B-irradiated plants survived temperatures below -8 degrees C, whereas control disks were killed at -6 degrees C. Cold hardiness did not significantly increase until September, when environmental cues such as decreasing day length and night temperatures also may have enhanced hardening. Our field findings confirm our previous laboratory study, demonstrating that elevated UV-B induces cross-protection to cold in Rhododendron leaf tissues.
authors.affiliation: Center for Urban Horticulture, Ecosystem Sciences Division, College of Forest Resources, University of Washington, Seattle, WA 98195-4115, USA. lindacs@u.washington.edu
authors.forename: Linda
authors.initials: L
authors.lastname: Chalker-Scott
authors.forename: James D
authors.initials: JD
authors.lastname: Scott
mesh_terms: D000064:Acclimatization / Q000528:radiation effects*; D003080:Cold Temperature; D004780:Environment, Controlled; D018384:Oxidative Stress; D010788:Photosynthesis / Q000528:radiation effects; D018515:Plant Leaves / Q000254:growth & development / Q000528:radiation effects; D029793:Rhododendron / Q000254:growth & development / Q000528:radiation effects*; D012621:Seasons; D013472:Sunlight; D014466:Ultraviolet Rays